012 FXUS66 KSEW 221805 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 1005 AM PST Sun Dec 22 2024 .SYNOPSIS...The active pattern continues with multiple frontal systems moving through the area bringing periods of rain, mountain snow, and gusty winds. The focus shifts towards Christmas into late next week with potentially higher-impact systems with heavy rain and snow and gusty winds, especially when combined with holiday travel. && .SHORT TERM /TODAY THROUGH TUESDAY/...No changes to the forecast this morning. In the wise words of the previous shift, it truly will be a rinse, later and repeat kind of day. Rain from the next system has arrived at the coast and will spread inland through the morning and into early afternoon. Gusty wind is expected along the coast, where a wind advisory has been posted. Wind is not expected to be an issue further into the eastern Puget Sound lowlands this time as the front is weaker. Monday will be drier due to short lived ridging between systems, but things certainly get more active thereafter. A stronger system will arrive Monday night, bringing more rain, mountain snow and gusty winds. Winds overnight into Tuesday will be gusty out of the southeast, with the Cascade gaps and eastern Strait of Juan de Fuca seeing the stronger wind gusts. By early Tuesday, the winds are expected to turn more southerly but remain elevated. Thereafter, the weather is going to continue to remain active, and given the holidays, it would be good to stay tuned to the forecast for updates as they relate to travel as there are likely going to be impacts whether across the Cascade passes or otherwise. .LONG TERM /WEDNESDAY THROUGH SATURDAY/...Christmas and the following days will be active weather wise as upward of four to five additional weather systems barrel into western Washington. On Wednesday, a strong and wet front will arrive for lowland rain and mountain snow, as the snow levels will be around 2500 feet. This may cause periods of heavy snow across the Cascade passes. Additionally, wind will be gusty, particularly in the afternoon from the south. Northern Puget Sound and eastern Strait of Juan de Fuca, as well as the immediate coast will likely see the strongest winds. Given the amount of precipitation expected, the series of storms and atmospheric rivers will be hydrologically impactful as well. Boxing Day remains wet as another system arrives with windy conditions expected area wide. Another one then is expected late in the week. Expect there to be more elevated rivers with possible flooding, and periods of snow across the Cascades. Kristell && .AVIATION...An approaching front will continue to spread widespread rain and increasing winds into the interior. While ceilings will gradually transition down into MVFR for most terminals through the day, gusty low level winds will also increase. Expect surface winds to gust to 20 kt this afternoon and into evening. The cold front will sweep through later tonight, with additional showers in the unstable post-frontal environment. Confidence too low for any thunderstorm mention in TAFs, but chances will be highest (around 20%) near the coastal terminals. Ceilings generally lower to widespread MVFR (local IFR possible) late tonight into early Monday. KSEA...VFR today in rain ahead of the approaching front. Brief lowering cigs/visibility possible late today in heavier rain. Southerly surface winds increase with gusts to 20 kt this afternoon. Ceilings likely drop toward MVFR after 12z through early Monday morning with winds easing. 12 && .MARINE...The next in a series of strong frontal systems will cross western WA today for another round of elevated wind and seas. Gales are forecast over the coastal waters and the eastern Strait of Juan de Fuca, with SCA winds across the northern inland waters. In addition, seas will build to 18 to 22 ft over the coastal waters throughout the day today. Additional strong frontal systems will impact the region through the week ahead, with even stronger winds forecast to move over area waters Tuesday morning with seas remaining elevated at 15 to 19 feet. Yet another strong storm system is on track to bring another round of potentially storm force winds on Wednesday to the outer coastal waters and at least Small Craft winds to the northern interior waters and Straits, with seas once again building to 17 to 21 feet. Additional headlines are possible heading towards the weekend as both seas and winds are expected to remain elevated. 15 && .HYDROLOGY...A series of frontal systems will move through the area this weekend into early next week and bring several rounds of precipitation. Widespread river flooding is not likely with these systems, minor rises on area rivers expected. The Skokomish River has briefly dropped below flood stage this morning but will begin to rise again this afternoon. Increasing precipitation around Christmas and into the end of next week could push the Skokomish back up to moderate flood stage. For the remaining rivers, the threat of flooding will also increase in the middle of next week as ensembles continue to indicate the potential for significant precipitation area-wide. While discrepancies remain, this most likely will lead to an increased chance of river flooding becoming more widespread and landslide concerns that may impact holiday travel. && .SEW WATCHES/WARNINGS/ADVISORIES... WA...Wind Advisory until 5 PM PST this afternoon for Central Coast- North Coast. PZ...Small Craft Advisory until 10 PM PST this evening for Admiralty Inlet-Grays Harbor Bar-Northern Inland Waters Including The San Juan Islands-West Entrance U.S. Waters Strait Of Juan De Fuca. Small Craft Advisory until 6 PM PST this evening for Central U.S. Waters Strait Of Juan De Fuca. Gale Warning until 6 PM PST this evening for Coastal Waters From Cape Flattery To James Island 10 To 60 Nm-Coastal Waters From Cape Flattery To James Island Out 10 Nm-Coastal Waters From James Island To Point Grenville 10 To 60 Nm-Coastal Waters From James Island To Point Grenville Out 10 Nm- Coastal Waters From Point Grenville To Cape Shoalwater 10 To 60 Nm-Coastal Waters From Point Grenville To Cape Shoalwater Out 10 Nm-East Entrance U.S. Waters Strait Of Juan De Fuca. Small Craft Advisory from 6 PM to 10 PM PST this evening for East Entrance U.S. Waters Strait Of Juan De Fuca. Small Craft Advisory from 6 PM this evening to 4 PM PST Monday for Coastal Waters From Cape Flattery To James Island 10 To 60 Nm-Coastal Waters From Cape Flattery To James Island Out 10 Nm-Coastal Waters From James Island To Point Grenville 10 To 60 Nm-Coastal Waters From James Island To Point Grenville Out 10 Nm-Coastal Waters From Point Grenville To Cape Shoalwater 10 To 60 Nm-Coastal Waters From Point Grenville To Cape Shoalwater Out 10 Nm. && $$

833 FXUS66 KPQR 222223 AFDPQR Area Forecast Discussion National Weather Service Portland OR 223 PM PST Sun Dec 22 2024 .SYNOPSIS...Rain showers continue tonight as a front moves through the area. Brief dry period tomorrow as most of the day should be dry, then rain spreads across region late afternoon through the night with showers Tuesday. A stronger frontal system slowly pushes across region Wednesday night into Thursday, bringing heavier rain, gusty winds, and high Cascade snow. Active weather continues into the weekend. && .SHORT TERM...Sunday afternoon through Tuesday...Showery conditions are being observed on radar this afternoon across NW Oregon and SW Washington as a frontal system impacts the PacNW. A weak warm front moved through the area this morning from the south, and satellite data shows the associated cold front is approaching the coast, located around 100-120 miles offshore as of 1 PM PDT. Widespread showers will continue ahead of the front as it moves through the area this evening, with scattered showers continuing overnight behind the front. Snow levels remain above 6000-7000 ft this afternoon, and are only expected to fall to around pass level 4000-5000 ft later tonight after the front passes and precipitation becomes more limited, so very limited snow accumulation is expected at pass level. A few stronger showers or thunderstorms are possible along and behind the front tonight, mainly along the coast and over the waters. Breezy south winds are being observed over the waters with gusts 35-50 mph at the buoys, which will continue this afternoon until the front passes. Breezy east winds continue through the Columbia Gorge into this evening with gusts up to 30-35 mph. A bit of a break in the rain tomorrow morning between frontal systems. Some patchy fog could form in low-lying valleys where winds are calm. Then the next frontal system begins pushing widespread rain into the area from the south late tomorrow afternoon ahead of the warm front, with the cold front making landfall tomorrow evening and moving quickly from west to east overnight. Scattered showers will continue Tuesday behind the front. Overall, this will be a very similar frontal system to the one current impacting the area. QPF amounts are around 0.25-0.75 inches for inland valleys, 0.75-1.25 inches for the coast and Coast Range, and up to 1.5-2 inches over the Cascades. Snow levels will once again rise above pass level with the warm front tomorrow afternoon and not fall to below pass level until early Tuesday morning. As this system does have slightly higher moisture over the Cascades due to a better orographic positioning, snow showers could produce up to 2-4 inches at pass level on Tuesday. -HEC .LONG TERM...Wednesday through Saturday...Ensembles indicate zonal upper level flow takes over briefly Tuesday night into Wednesday morning. Will likely see another brief break from the rain, though the coast could see some drizzle. Then, a more potent frontal system remains directed at Washington and Oregon for Wednesday afternoon/evening into Thursday. GFS and Euro ensembles are coming into better agreement on indicating this system is a moderate to strong atmospheric river with an IVT plume of around 750 kg/ms aimed directly towards Oregon. 13z NBM run indicates fairly steady most likely scenario and high end scenario of 48 hour QPF ending 4 AM Friday from previous forecasts (2-5 inches and 6-8 inches over the coast, Coast Range, and Cascades and 1.5-2 inches and 2.5-3 inches for the interior lowlands, respectively). However, the low end 10th percentile scenario has increased from previous forecasts with 1.5-4 inches over the coast, Coast Range, and Cascades, and 0.75-1.5 inches over the interior lowlands. Rises on rivers are possible, especially those in the Coast Range and Willapa Hills. However, flooding may not become a concern until later in the week after the next frontal system or two produces additional rain Friday into Saturday. Details are much more uncertain on specifics with the late-week storms, but overall, HREF guidance indicates a 25-45% chance of rivers along the Coast Range and Willapa Hills reaching minor flood stage anytime late Thursday through the weekend. Wind will also be more of a factor with these storm systems. NBM indicates a 50-75% chance of wind gusts over 50 mph and 20-50% chance of wind gusts over 60 mph along the coast with each frontal system Wednesday night through Friday. Inland, there`s a 30-50% chance of wind gusts exceeding 40 mph. Additionally, more Cascade snow is forecast with these systems as snow levels won`t be able to rise as much in between each system. Snow levels will mostly remain around 4500-5500 ft. The latest forecast indicates around 1 foot of snow at pass level from Wednesday night into early Saturday morning, though the 90th percentile high end scenario indicates up to 2 feet is possible. Keep an eye on the forecast as these systems become better resolved. -HEC && .AVIATION...Showers continue through the evening as moisture associated with the cold front lingers. Conditions dry out overnight. Gusts up to 20 to 30 knots are anticipated along the coast and at KTTD. Once the front through, coastal terminals see a 80% chance of MVFR cigs, while inland TAFS see around a 40-60% chance of MVFR or lower ceilings from around 00-06z Mon onwards. Clouds break up a bit overnight leading to potential fog development within the southern Willamette Valley between 15-21Z. PDX AND APPROACHES...Likely VFR condition throughout most of the TAF period. Showers continue through the evening before tapering off. Sporadic gusts up to 15-20 kt may be possible. Around a 50-70% chance of MVFR cigs from 01-03z Mon onwards but confidence in the exact timing of this change is only moderate. -Batz && .MARINE...Weather system after weather system will parade through the coastal waters the week as a broad upper-level low holds in place over the eastern Pacific. Solid Gales continue across all zones and the Columbia River Bar but Storm force winds are starting to look less likely given the observations from buoy 46089 which has had peak wind gusts around 40 kt. Winds will start to drop off this evening, dropping below Gales after 5-6 PM. Waves will peak 3 to 4 hours later. Hazardous Seas Warnings are in place from 7 PM this evening until 4 PM Monday. Moving into Monday we`ll see the arrival of a long period swell (~20 seconds) with significant wave heights likely peaking in the 19-21 foot range. Another quick hitting front will move through the area Monday evening into Monday night with another period of solid Gales after 7 PM Monday. After a lull of wave heights back into the teens Tuesday into early Wednesday morning a stronger system mid to late week will increase winds to at least Gales and usher in seas near 20 feet yet again. The NBM now projects a 25-40% chance for Storm Force (>48 knot) gusts on Wednesday across the outer waters. Mariners should be prepared for continued hazardous conditions through the end of the week into next weekend as the active pattern continues. -Batz/Schuldt && .BEACH HAZARDS...A large, energetic westerly swell will continue to build over the coastal waters into Monday. Seas in excess of 18 to 20 feet with a period of around 19-21 seconds will likely result in breaking waves approaching 25 to 30 feet in the surf zone. The High Surf Advisory will be maintained through Monday evening. Forecast period and wave heights continue to show marginal surf energy for the peak of the swell. Continue to monitor future forecasts for changing conditions. Beachgoers should be prepared for dangerous surf conditions and large waves running far up onto the beach into early next week. -Schuldt/Batz && .PQR WATCHES/WARNINGS/ADVISORIES... OR...High Surf Advisory until 10 PM PST Monday for ORZ101>103. WA...High Surf Advisory until 10 PM PST Monday for WAZ201. PZ...Gale Warning until 7 PM PST this evening for PZZ210. Hazardous Seas Warning from 7 PM this evening to 4 PM PST Monday for PZZ210-251>253-271>273. Storm Warning until 7 PM PST this evening for PZZ251>253-271>273. && $$ www.weather.gov/portland Interact with us via social media: www.facebook.com/NWSPortland x.com/NWSPortland

680 FXUS66 KMFR 222148 AFDMFR Area Forecast Discussion National Weather Service Medford OR 148 PM PST Sun Dec 22 2024 .SHORT TERM...Active weather continues through Christmas Eve as a couple front move across the area. The first of these is moving inland today. Ahead of this front snow levels have risen to around 6000-7000 feet. Light rain has begun to spread inland from the coast to the Cascades. Rain will increase later this afternoon and evening. Precipitation chances will diminish late this evening into early Monday morning as the front gradually shifts eastward. Additionally, this front is bringing some gusty winds to the area. South winds have increased over the mountains, in the Shasta Valley and in southern portions of the Rogue Valley. Gusts to around 40-50 mph are expect for these areas. A wind advisory (NPWMFR) remains in effect through this evening. Then, expect a brief break in the weather before a second, slightly stronger front moves into the area Monday afternoon through Tuesday (Christmas Eve day). Models shows this system will bring slightly stronger winds to the area as a mid level jet of 50-60 kt moves over the area and a moderate surface pressure gradient develops (-8 mb Medford to Redding). Winds are expected to reach advisory levels (with gusts of 40 to 55 mph) in the southern Rogue Valley and east of the Cascades over the higher terrain and in the Summer Lake area. In the Shasta Valley, models and guidance support gusts to 45-60 mph (60% chance for gusts to 60 mph), with strongest winds for areas in and near Weed. See the NPWMFR for details. Additionally, this is a moist front which gradually moves across the area late Monday through early Tuesday, so expect more precipitation with this system. Snow levels are expected to be high (6000-8000 feet) as precipitation spreads inland late Monday through Monday night, with most areas seeing moderate to locally heavy rain. Heaviest rainfall (1.5-3 inches in about 12-18 hours) is expected Monday night across Curry, southwest Josephine and western/south- central Siskiyou counties. The front shifts east of the Cascades late Monday night into Tuesday morning. Behind the front, an upper trough moves inland with additional showers through the day Tuesday, then decreasing chances for showers by late Tuesday evening. With the frontal passage, Monday night and early Tuesday morning, expect cold air to move into the area and snow levels to lower to 4000-5000 feet. Then showers continue on Tuesday with the upper trough overhead. These will result in some light snow over higher mountain passes. While snowfall amounts are generally light, with 1 to 4 inches on higher passes in the southern Oregon Cascades, mountains in western Siskiyou County and over the Warner Mountains, this has a potential to impact holiday travel due to occuring during the day on Christmas eve. Crater Lake may see higher totals closer to 5 to 6 inches. Highway 97 is also expected to see light snow (around 1-2 inches) Tuesday morning. For I-5 near Siskiyou Summit, snow levels may lower to near or just above pass level. This is forecast to resultin a rain/snow mix and periods of snow in showers. Travelers should be prepared for the potential for light snow on mountain passes and periods of light snow along Highway 97, mainly north of Chiloquin. && .LONG_TERM... Christmas Day through Sunday...An active weather pattern will continue. Christmas Day for the region looks uneventful as high pressure prevails in the wake of the Christmas Eve trough. Some overrunning will be occurring and there is a chance (50-70%) for some light rain/high mountain snow from the Cascades west. Christmas night through Thursday looks wet and windy as a fairly energetic system moves inland across the region with strong onshore flow. Snow levels will be 4500-5000 feet during this time and our forecast remains consistent for another 6-12 inches at the local areas ski resorts (Willamette Pass, Mt. Ashland, Mt. Shasta). The high country around Crater Lake could receive over a foot in the 24 hour period ending 4pm Thursday (60% chance per NBM). A hefty onshore Pacific Jet remains aimed at Oregon Thursday Night through the weekend with periodic shortwaves. The NBM shows a 60-75% chance for three day precipitation totals of at least 3 inches across the south coast through Josephine and western/southern Siskiyou counties. Also, similar amounts are possible across the Cascades from Willamette Pass to Highway 140. As a result of this extended wet period, our attention has been shifting to flood potential for the coast region and perhaps some areas of Douglas, Josephine and Siskiyou counties for late next weekend into early in the week after Christmas. Please remain alert for this potential. Stavish && .AVIATION...22/18Z TAFS...Incoming strong front currently bringing widespread mountain obscuration, showers and gusty south wind west of the Cascades. Areas of low level wind shear with south to southwest wind 40 to 50 kts at 2000 feet agl. Condition spreading east of Cascades this afternoon. Winds easing after 00z and showers ending after 06z. Areas of LIFR valley fog across the west side developing after 06z with east side possibly seeing local LIFR fog as well after 12z. Expect widespread LIFR conditions for the inland west side 12z-18z Monday but widespread MVFR to VFR should prevail at the coast and over the east side. Stavish && .MARINE...Updated 200 PM PST Sunday December 22, 2024...Very high, steep, and chaotic mixed seas will be a persistent feature in the marine waters through much of the forecast period. Multiple strong fronts will pass through the area this afternoon and through the holiday week, bringing multiple rounds of gale force south winds, with storm force gusts a possibility with each front. The latest front is approaching the western edge of the outer waters right now and is expected to move onshore late this afternoon or early evening. South gales and very high, steep, and chaotic mixed seas will continue until the front passes. Residual wind wave/fresh swell along with a heavy background west swell will keep very high and steep combined seas going between this front and the next front (tonight through Monday morning). The next strong front arrives later Monday. As a deepening low pressure moves south-to-north near 130W Monday afternoon and evening, pressure gradients will be tighter with this front, and as a result winds will be stronger - gales at least and storm force winds are possible. A gale watch remains in effect for this front, but we continue to evaluate the potential for worse conditions. Conditions briefly "improve" as seas lower below 15 feet late Tuesday into early Wednesday (Christmas Day), but seas will remain high and steep with conditions hazardous to small craft likely during this time. Yet another deep low pressure system and strong front is expected late Christmas day into Thursday. High end gales look likely with this front, possibly even storm force. Guidance continues to fluctuate with respect to the height of the swell train behind the Christmas front, but seas will continue to be very high, steep and chaotic into next weekend. -Wright && .BEACH HAZARDS...Updated 200 PM PST Sunday, December 22, 2024... Numerous fronts will bring periods of increasing swells and dangerous surf conditions this weekend and through next week. A High Surf Advisory remains in effect through this evening, with large breaking waves of 21 to 26 feet expected. It will be followed immediately by a High Surf Warning from late this evening through Monday evening as the next, stronger front will bring dangerously large breaking waves of 25 to 33 feet. Conditions are expected to slowly improve on Tuesday, but another round of dangerous surf conditions can be expected late Wednesday (Christmas Day) through Thursday, if not longer. Extremely large breaking waves will create very hazardous conditions along beaches and area shorelines. Waves will inundate beaches and surge into normally dry areas. Infrastructure damage and significant beach erosion can be expected. Stay away from area beaches during this period of active weather. -Wright/BR-y && .MFR WATCHES/WARNINGS/ADVISORIES... OR...Wind Advisory until 7 PM PST this evening for ORZ026-030-031. High Surf Advisory until 10 PM PST this evening for ORZ021-022. High Surf Warning from 10 PM this evening to 4 AM PST Tuesday for ORZ021-022. CA...Wind Advisory until 7 PM PST this evening for CAZ081-085. High Wind Warning from 1 PM Monday to 1 AM PST Tuesday for CAZ081. PACIFIC COASTAL WATERS...Gale Warning until 7 PM PST this evening for PZZ350-356-370-376. Hazardous Seas Warning from 7 PM this evening to 1 PM PST Monday for PZZ350-356-370-376. Gale Watch from Monday afternoon through late Monday night for PZZ350-356-370-376. && $$ CC

102 FXUS66 KEKA 221411 AFDEKA AREA FORECAST DISCUSSION National Weather Service Eureka CA 611 AM PST Sun Dec 22 2024 .SYNOPSIS...Increasing southerly winds expected this morning as another frontal system moves through the area. A brief dry period will lead into the onset of a more impactful system Monday night into Tuesday. Increasing hydrologic impacts are expected by midweek, with additional rainfall likely through next weekend. && .DISCUSSION...The area remained mostly dry overnight beneath this brief period of ridging aside from some light radar returns. Mid level cloud cover will gradually lower this morning as another storm system approaches the coast. Low level wind shear is already prevalent with gusts exceeding 30 mph on higher terrain. Winds will continue to increase and mix down to the surface as the front approaches; hi-res models continue to highlight a strong low level jet with max winds exceeding 60 to 65 knots. A wind advisory is in effect for elevated terrain in Humboldt and Del Norte counties as well as exposed headlands around Cape Mendocino. Gusts 25 to 40 mph are possible along lower elevations on the coast, including Crescent City. Precip along the leading north end of this fast moving front is expected to arrive late this morning (around 10 am) while areas of Mendocino and Lake county may not see rainfall begin until 4-5 PM. Periods of heavier rainfall is possible, especially along the the north coast where the convective environment is a bit more favorable for isolated thunderstorms. WPC storm totals are similar to yesterday, with 0.50 to 1.25 inches and locally higher amounts approaching 1.5-1.75 in the King Range. Much like this last system, interior Trinity and Lake county will be on the lower end of the spectrum. Scattered showers will likely continue even after the heaviest rainfall tapers off late this evening. Another period of brief ridging will keep the first half of Monday mostly dry and unseasonably warm with consistent SW flow. The most impactful AR system is still on track to arrive late morning into early afternoon, beginning with warm frontal precipitation in Mendo/Lake counties. Near term model guidance is in good agreement on widespread heavy precipitation late Monday afternoon through early Tuesday morning as a strong cold front follows behind. GFS and WPC are forecasting widespread 2 inches to nearly 4 inches in portions of interior Del Norte and along the King Range while ECMWF is nearly 0.50 to 1.0 inches lower, but leaning toward higher totals given ample moisture transport. A fair amount of model spread is still prevalent on the strength and timing of strong winds associated with the front and low level jet. Hi-res models have gusts exceeding 30 mph beginning as early as mid afternoon, while ensembles are leaning closer to 00Z. With another strong jet max, NAM gusts are currently exceeding 45-50 mph in Crescent City and elevated terrain in interior Del Norte and Humboldt. Widespread gusts 25 to 40 mph are possible, especially along the coast. Strongest winds are likely to accompany heavy rains through late Monday evening. A more substantial break is still expected Tuesday afternoon through late Wednesday. CNRFC forecasts are still favoring rapid river rise late Tuesday into Wednesday following the rainfall, but have backed off a bit to just under action/minor flood state (see hydrology section). Additional 1 to 3 inches of precip still expected for the next system late Wednesday into Thursday. Lower snow levels (2500 to 3000 feet) Christmas Day will quickly rise in time for this additional precipitation, but GFS is beginning to note a cold pool <5000 feet in the Trinity Alps through early Thursday morning. Snow impacts will need to watched closely as several inches are possible at Scott Mountain Pass before a warmer air mass drives snow levels up again. && .AVIATION...As previously stated in prior discussions, a series of frontal boundaries will continue for the next few days, introducing gusty southerly winds, precip, and vicinity thunderstorms. KCEC and KACV are likely to see low level wind shear before the gusts mix down this morning. Rain is also soon to follow just before the afternoon with probabilities of thunderstorms above 15% - 20% at the coastal terminals. Flight categories may dip to IFR by the late afternoon as ceilings and visibility drop with rain becoming more established. KUKI will meet similar conditions without the gusts and wind shear. IFR setting in at KUKI by the early evening with rain and lower ceilings. /EYS && .MARINE...Unsettled and hazardous conditions in all area waters after the previous passage of a frontal boundary and the development of sizable/considerable westerly swell. Winds are forecasted to increase again this morning, leading to gale force gusts over the northern outer waters initially and spreading this afternoon with gusts up to 45kts. After the passage winds will calm significantly before strengthening again Monday midday as yet another front passes over the coastal waters. This repetition of stout boundaries with dynamic fetch in the same direction will continue to send large long period swells into the waters. In conjunction to the strong winds and associated wind waves, seas will continue to be chaotic. /EYS && .HYDROLOGY...Forecast is still on track for additional rainfall totals 0.5 to 1.5 inches by this evening, with the highest totals in the higher terrain of interior Del Norte and Humboldt. A stronger system is expected Monday night into Tuesday with more significant rain impacts as IVT values exceed 500 kg/m/s. WPC is outlining a marginal excessive rainfall outlook for most of the CWA on top of increasingly saturated soils, with 2 to 4 inches of rainfall currently forecast. CNRFC deterministic river forecasts have backed off slightly to just under action/minor flood stage Wednesday - there is still a 25 to 40% chance of exceeding action/minor flood stage for the Mad River at Arcata, the Eel River at Fernbridge (slightly exceeding monitor), the Russian River at Hopland and the Navarro River. Impacts are expected for small streams and flood susceptible areas. NBM probabilities are still showing 1 to 3 inches of rainfall by Thursday evening, the higher end of which will once again land in Del Norte and the King Range. River ensemble forecasts are already showing responsive tendencies after only briefly being able to diminish on Wednesday. For the end of the week: WPC and CPC continue to emphasize risk for excessive rainfall Friday through Sunday. && .BEACH HAZARDS...A long period, westerly swell will continue to impact the coastal waters of Northwest California through the week. The current swell is expected to bring breakers between 20 to 22 feet with a brief pause before longer period swell trains of varying wave heights combine to constructive interference, resulting in large breakers. A high surf warning will likely be hoisted for the early evening around 4 or 5pm, as the arrival time on shore is speculative. Hazardous surf conditions due to the breaking waves will be possible along west-northwest facing beaches and will peak Monday afternoon around 28 - 29ft. High surf conditions will continue from the early afternoon through the evening on Monday. /EYS && .EKA WATCHES/WARNINGS/ADVISORIES... CA... High Surf Advisory until 9 AM PST this morning for CAZ101- 103-104-109. Wind Advisory from 7 AM this morning to 4 PM PST this afternoon for CAZ102-104>106. NORTHWEST CALIFORNIA COASTAL WATERS... Hazardous Seas Warning until 9 AM PST this morning for PZZ450-475. Gale Warning from 9 AM this morning to 3 PM PST this afternoon for PZZ450-475. Hazardous Seas Warning until 3 PM PST this afternoon for PZZ455. Gale Warning until 3 PM PST this afternoon for PZZ470. && $$ Visit us at https://www.weather.gov/eureka Follow us on Facebook and Twitter at: https://www.facebook.com/NWSEureka https://www.twitter.com/NWSEureka For forecast zone information see the forecast zone map online: https://www.weather.gov/images/eka/zonemap.png

548 FXUS66 KMTR 221844 AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 1044 AM PST Sun Dec 22 2024 ...New AVIATION... .SYNOPSIS... Issued at 229 AM PST Sun Dec 22 2024 A parade of systems will bring compounding impacts to the Bay Area and Central Coast. Life-threatening bay, ocean, and beach conditions linger through next week. && .UPDATE... Issued at 940 AM PST Sun Dec 22 2024 The inherited near term forecast is in good shape, with only some minor tweaks to PoPs and Wx grids needed to address ongoing trends. Widespread drizzle/mist and some pockets of fog continue this morning. Modest ascent, as inferred by traditional water vapor imagery, ahead of the next upper trough coupled with a moist lower troposphere continues to encourage the development of drizzle, mist, and fog. In fact, AlertCalifornia web cameras show that even interior portions of the East Bay are quite damp this morning with low clouds and drizzle. I`ve inserted drizzle into the forecast for most areas, except far the extreme northern portions of the North Bay and far southern Monterey and San Benito counties where webcams show more in the way of clouds (even some peaks of sunshine). I anticipate that this will continue through at least early afternoon, though there is some potential that drizzle could linger a little later. If so, we`ll make adjustments to the worded forecast with the main afternoon forecast update. Otherwise, our lull in actual rain showers is anticipated to continue until late this afternoon when more numerous shower activity begins to impact the North Bay ahead of our next system. Tonight into Monday morning does appear that we`ll see more widespread rainfall and the details outlined in the previous discussion remain valid. Updated products will be transmitted soon. && .SHORT TERM... (Today and tonight) Issued at 229 AM PST Sun Dec 22 2024 Light rain can be expected today thanks to a weak frontal boundary across Central California which will allow for precipitation up to 0.25" in orographic lift favored locations like the East Bay Hills, Eastern Santa Clara hills, Santa Cruz Mountains, and the Santa Lucia Mountains. A cold front will move through tonight providing another shot of rainfall with totals on the order of 0.25"-0.75" for the North Bay, up to 0.25" for the rest of the Bay Area, with drizzle at best in Monterey and San Benito Counties. A High Surf Warning will replace the High Surf Advisory at 4 PM with life-threatening beach and ocean conditions lingering into next week. && .LONG TERM... (Monday through Saturday) Issued at 229 AM PST Sun Dec 22 2024 Key Messages: *Parade of storm systems through next week *Most impactful storm appears to be Monday into Tuesday *Rainfall totals between today and Saturday: North Bay: 2"-6", locally up to 9", rest of the Bay Area: 1-4", Central Coast: 0.25"-1.50", locally up to 5" in the Santa Cruz Mountains and locally up to 3" along the Big Sur Coast *Wind gusts up to 45 mph on Tuesday *Life-threatening beach and ocean conditions linger into next week. A widespread impactful system will move through the region Monday afternoon through Tuesday afternoon. Rainfall totals up to 2.50" are forecast for the higher terrain of the North Bay with a gradual taper in rainfall amounts from north to south with higher rainfall totals expected in higher terrain. The greatest impacts are expected in the North Bay as portions of Marin, Napa, and Sonoma Counties have been highlighted by the Weather Prediction Center (WPC) for a marginal/at least 5% risk of rainfall exceeding flash flood guidance between 4 AM Monday and 4 AM Tuesday. This means that isolated flash floods will be possible and that their nature will be localized and primarily affecting places that can experience rapid runoff with heavy rainfall. Fortunately, no mainstem river forecast points are forecast to reach minor flood stage according to deterministic forecasts; however, rivers and their creeks and streams will have no problem responding quickly to rainfall. While it is too early to issue any wind headlines, there is increasing probability of wind gusts reaching or exceeding 45 mph during this system. Whether southerly winds meet Wind Advisory criteria or not, soils approaching saturation in addition to tree damage from last weekend`s storms will allow for plentiful tree debris. Isolated thunderstorms will also be possible with this system with the Storm Prediction Center (SPC) highlighting all counties with the exception of Monterey and San Benito for general or non-severe thunderstorms between 4 AM Tuesday and 4 AM Wednesday. Remember that lightning and flooding threats exist with all thunderstorms. An ECMWF point sounding forecast for STS at 10 AM Tuesday shows that the environment will be that of low CAPE and high shear, but that the parcel will have to overcome a stable lapse rate in the 850-700 mb layer. Wednesday will be dry, giving rivers and their creeks and streams in addition to soils a chance to somewhat dry out ahead of more rainfall. Another cold front moves through the region Thursday bringing rainfall totals of up to 1.00" in the higher terrain of the North Bay with a stout tapering of rainfall totals from north to south with interior Monterey and San Benito County not expecting to receive any rainfall. Friday and beyond is unfortunately where confidence begins to wane. Global ensemble clusters are depicting the potential for zonal flow across much of the region which would deflect systems to the north of the region; however, there may be just enough troughiness over the North Bay to allow for more impactful rainfall with the help of some shortwave troughs. && .AVIATION... (18Z TAFS) Issued at 1028 AM PST Sun Dec 22 2024 Light rain showers leftover from this morning have mostly ended across the area, with light drizzle and local fog impacts lingering into this afternoon. Otherwise complicated cig forecast with mixed skies and multiple systems moving in with only short windows in between. Current forecast is largely IFR cigs for nearly all terminals through the TAF period, with some clearing to SCT this afternoon for areas south of the SF Bay. Moderate confidence in timing of major features such as rainfall, but a bit less confidence in exact degree of reduced vis and cig height, especially after the expected rain this evening. Showers this evening move out late tonight with lingering cloudiness and drizzle into Monday morning. Vicinity of SFO...Difficult forecast this issuance due to mixed skies and multiple weather systems in rapid succession. Currently thinking mostly IFR cigs with brief improvements to MVFR this afternoon as the next cold front approaches and mixes the airmass a bit. However, conditions are likely to fall back to IFR in the post-frontal environment after the rain showers end tonight, lasting into Monday morning. SFO Bridge Approach...Similar to SFO. Monterey Bay Terminals...Gloomy conditions persist through much of the period with IFR/MVFR cigs lingering throughout. Moderate chance of clearing to VFR this afternoon under SCT skies, but will likely return to IFR tonight as another weak cold front passes through. && .MARINE... (Today through Friday) Issued at 229 AM PST Sun Dec 22 2024 Large, building westerly swell continue into Sunday morning with a temporary decrease in swell later Sunday. Then, a large to very large westerly swell is expected Monday into Tuesday. Wave heights will remain elevated through late next week with 15 to 20 foot waves Monday through Wednesday. Expect dangerous conditions for small crafts through the weekend and into midweek. Elevated seas will continue to produce enhanced shoaling at harbor entrances and bars. && .BEACHES... Issued at 353 AM PST Sun Dec 22 2024 High surf advisory remains in effect through this afternoon for elevated surf of 20-26 feet, with breakers up to 30 feet. A long period, westerly swell will continue to create hazardous beach conditions along the coast into Tuesday. Global wave models are forecasting a more intense and energetic swell with 20+ feet heights and swell periods of 20+ seconds, this will lead to much higher breakers of 30-35 feet, and up to 40 feet at favored spots such as Mavericks. Localized coastal flooding impacts are also likely, especially during high tide. As such, a High Surf Warning has been issued from 4 PM this afternoon through noon Tuesday. These conditions will result in dangerous and life-threatening bay, ocean, and beach conditions lingering into next week. && .MTR WATCHES/WARNINGS/ADVISORIES... CA...High Surf Advisory until 4 PM PST this afternoon for CAZ006-505- 509-529-530. High Surf Warning from 4 PM this afternoon to noon PST Tuesday for CAZ006-505-509-529-530. PZ...Small Craft Advisory until 3 AM PST Tuesday for Mry Bay-Pigeon Pt to Pt Pinos 0-10 nm-Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 0-10 nm-Pt Arena to Pt Reyes 10-60 NM-Pt Pinos to Pt Piedras Blancas 0-10 nm-Pt Reyes to Pigeon Pt 0- 10 nm. && $$ SHORT TERM...Sarment LONG TERM....Sarment AVIATION...Behringer MARINE...Behringer Visit us at www.weather.gov/sanfrancisco Follow us on Facebook, Twitter, and YouTube at: www.facebook.com/nwsbayarea www.twitter.com/nwsbayarea www.youtube.com/nwsbayarea

328 FXUS66 KOTX 221752 AFDOTX Area Forecast Discussion National Weather Service Spokane WA 952 AM PST Sun Dec 22 2024 .SYNOPSIS... Unsettled weather will continue for much of this week, with mild temperatures and precipitation falling primarily as valley rain and mountain snow. Check mountain pass forecasts and conditions often before traveling. Periods of heavy mountain snow will be possible late in the week. && .DISCUSSION... Morning update: Visibility has improved on several web cams around the Moses Lake and Ritzville areas, while Waterville remains in dense fog. The Dense Fog Advisory has been cancelled for the Moses Lake and Upper Columbia Basin with the HREF showing continued improve visibility into the early afternoon, while extended until 1 PM for the Waterville Plateau where the dense fog is expected to persist. JW && .AVIATION... 18Z TAFS: Southeast winds ahead of an incoming weather system is helping to bring some drying in the boundary layer across SE Washington and the Spokane/Coeur d`Alene area with improving CIGS. Meanwhile dense fog down in the LC Valley is expected to gradually lift as the southeast boundary layer winds increase. The northern valleys and areas near the Cascades are likely to remain in IFR/MVFR stratus through the day as moisture gets pooled up in these areas. Then the incoming weather system will spread light rain into the region from west to east crossing into Central WA late this afternoon and then Eastern WA/N Idaho this evening and overnight. As southeast boundary layer winds shift to southwest, CIGS will again drop to IFR and MVFR across the Spokane/Coeur d`Alene area and Palouse overnight into Monday morning. JW FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: There is moderate confidence that KGEG/KSFF/KCOE will be VFR this afternoon, and high confidence for VFR at KPUW. Fog trapped down in the LC Valley with lower confidence as to timing and degree of improvement through the afternoon. Seeing signs of improvement on web cams south and east of KMWH, matching the HREF probabilities of timing of improvement leading to moderate confidence in improving conditions through 21z for KMWH. As the boundary layer winds winds shift back to SW overnight, the HREF suggests nearly a 100% chance that GEG will drop back down to IFR between 10-12z Monday. JW ----------------------- Confidence descriptors: Low - Less than a 30 percent chance Moderate - 30 to 70 percent chance High - Greater than a 70 percent chance For additional probabilistic information for NWS Spokane airports, please refer to the Aviation Dashboard on our webpage: https:/www.weather.gov/otx/avndashboard && .PREV DISCUSSION... /issued 423 AM PST Sun Dec 22 2024/ Through Monday night: Areas of fog and low stratus will prevail this morning across portions of the Inland Northwest, especially in valleys that typically favor fog development. A disturbance will push through the region later today and is anticipated to bring widespread precipitation as it moves west to east from the Cascades into eastern WA and northern ID. Expect mainly rain across populated valleys and snow generally confined to elevations of 3000-3500 feet (lower in sheltered valleys in the lee of the Cascades) and above, including light accumulations for several mountain passes. A shortwave ridge quickly passes thru on Monday, with a brief period of drier conditions likely for the forecast area. /KD Tuesday through Saturday: An active, unsettled pattern continues through next weekend with several rounds of precipitation in store for the Inland Northwest. Monday night into Tuesday a compact low pressure system will make landfall along the coast of British Columbia, bringing snow to the Cascades and northern mountains and rain elsewhere. A brief lull in precipitation will occur Wednesday (Christmas) morning and afternoon before a more robust system moves in Wednesday evening. Snow amounts with this system have trended upward over the past few ensemble runs for the Cascade Passes, so monitoring pass conditions will be crucial if you`re planning on traveling after the holiday. Based on current guidance, lowland areas could potentially see some snow Wednesday night too, but uncertainty is high at this point. A wet, troughing pattern persists through the end of the week delivering additional rounds of precipitation to the Inland Northwest. /Fewkes && .PRELIMINARY POINT TEMPS/POPS... Spokane 41 37 41 35 43 31 / 10 80 10 50 80 10 Coeur d`Alene 41 35 41 34 41 32 / 10 90 30 30 90 30 Pullman 43 38 45 37 40 30 / 10 100 20 50 90 30 Lewiston 48 41 50 39 47 34 / 10 90 10 30 90 20 Colville 37 33 39 32 39 28 / 30 90 10 40 90 10 Sandpoint 38 34 39 33 38 29 / 10 90 70 30 90 40 Kellogg 41 36 39 34 39 34 / 20 90 80 30 100 50 Moses Lake 41 35 42 36 44 29 / 40 70 0 80 50 0 Wenatchee 37 33 39 35 41 30 / 70 60 0 80 40 0 Omak 36 32 39 34 39 28 / 50 90 0 70 50 0 && .OTX WATCHES/WARNINGS/ADVISORIES... ID...None. WA...Dense Fog Advisory until 1 PM PST this afternoon for Waterville Plateau. && $$

372 FXUS66 KPDT 222234 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 234 PM PST Sun Dec 22 2024 .SHORT TERM... Tonight through Tuesday night...Two systems will impact the region during the short term period. The first will be tonight into Monday morning and the second system will be later Monday into Tuesday. Drying is expected to move in for Tuesday night... Christmas Eve. As the first system moves inland late this afternoon/early evening, precipitation will increase from west to east across the region. Snow levels are quite high...generally 4500-5000 feet in the Washington Cascades and 6500-7500 feet elsewhere. With snow levels that high, precipitation will be rain almost everywhere. Snow levels do fall a bit by morning, but the bulk of the precipitation is over by then. The next system arrives Monday evening/night and continues into Tuesday. Snow levels remain quite high with this system on southwesterly flow. The trough associated with this system will pass through the Pacific Northwest Tuesday afternoon. Snow levels will decrease substantially behind the trough, but again the bulk of the precipitation will be over with by this point. Snow levels will decrease from 3500 feet over the Washington Cascades to 6500-7500 feet elsewhere on Tuesday to 2500-3500 feet across the area by Wednesday morning. Snow accumulations with both systems are expected to be light, except at the highest elevations and along the crests. Liquid equivalent QPF will be 0.25 to 0.5 inches in the mountains with the first system and 0.10 to 0.20 in most of the lower elevation areas. This is a slight increase in QPF. With the second system, liquid equivalent QPF is 0.50 inches to 0.75 inches in most of the higher terrain, with 0.75 to 1.00 inches in the highest terrain. Most of the lower terrain will receive 0.25 inches or less with portions of the Basin and central Oregon, Kittitas and Yakima Valley receiving less than 0.10 inches. This is a decrease in QPF from previous runs. ECMWF EFI indicates a large swath of 0.8 to 0.9 anomalies for QPF across much of eastern Oregon on Tuesday. Winds will increase Monday night into Tuesday as the southwesterly flow increases ahead of the trough with the warm front. The greatest areas of concern are the Grand Ronde Valley and the base of the Blue Mountains. Pressure gradients between Baker City and Meacham do go over 5 mb late Monday night into Tuesday morning. Will need to keep an eye on these areas for potential headlines. NBM wind gust probabilities indicate 50 to 70% probabilities for wind gusts to 39 mph but only about 30% probabilities for wind gusts to 47 mph. High temperatures will range 5 to 10 degrees above normal in many lower elevation locations. .LONG TERM... Christmas Day through Sunday...A wet and windy holiday week is in store for the forecast area, as models continue to be in good agreement on a series of warm fronts and amplified W to SW flow impacting the region through at least around New Years. One saving grace to the forecast when it comes to holiday travel is that snow levels look to remain quite elevated for the week, holding steady at around 3500-4500 feet for the majority of the period. That being said, with how much moisture models are having us receive through the week, hydro concerns could arise, especially downslope of the Cascades and Blues. Christmas Day starts out with a shot of cold and dry air filling in from behind a departing trough, before the evening becomes wet with the arrival of a shortwave from the WSW. This system has just enough cold air trailing it that the best chances for snow across the WA Cascade passes looks to be associated with this system, however confidence is on the lower end (30-40%) of Snoqualmie and White Passes seeing accumulating snow beyond a couple of inches given how borderline snow levels appear to be. Could see lighter snow across Santiam Pass and even Meacham, but as of now, the most forecast variability when it comes to ptype lies with this system. A warm front then lifts through around the overnight period Thursday into Friday. Consensus across models is that this looks to be a particularly wet system, with moderate to high confidence (50-60%) in the Cascade crests seeing over an inch of QPF, and moderate confidence (40-60%) for our population zones seeing at least a quarter of an inch of rain. This warm front looks to be robust enough to keep snow levels more elevated at above 4000 feet for WA, increasing southward towards Oregon, but the high mountains within the northern Blues (think Tollgate, Ski Bluewood) would see decent snowfall given how moisture-laden this system looks to be. Elsewhere, winds downslope of the Blues and mountains of central Oregon are expected to pick up, more so with this warm front than any other system in the period, although confidence is high (70-80%) in persistently breezy conditions for the aforementioned areas under this pattern. Models hint at an atmospheric river setting up over the PacNW next weekend, with confidence moderate-high (50-60%) given the relative lack of disagreement across ensembles. Looking at river gauge forecasts, some gauges along the east slopes of the Cascades and foothills of the Blues are nearing action stage by the beginning of next week. Will certainly be something to keep an eye on, as again, this wet pattern looks to hold steady beyond even the period and into the start of the new year. Evans/74 && .AVIATION... 00z TAFs...Low clouds and fog continue to persist for many sites this afternoon as rain moves through the forecast area. ALW in particular has seen dense fog move in this afternoon. Expectation is that as rain moves through, sites will see relief in the form of improved visibilities and slightly improved cigs, however cigs below 5 kft are expected to persist for most sites through tomorrow morning. Fog may also redevelop for some sites in the Basin overnight, however confidence in this occurring is low to moderate (30-40%). Expect light winds less than 10 kts to continue, except for some breeziness in BDN/RDM as this ongoing system moves through the area. Evans/74 && .PRELIMINARY POINT TEMPS/POPS... PDT 38 52 40 46 / 90 0 80 80 ALW 40 53 41 48 / 100 10 70 90 PSC 38 51 40 48 / 60 0 90 70 YKM 31 43 34 45 / 70 0 100 30 HRI 38 51 41 48 / 60 0 80 70 ELN 32 41 34 44 / 60 0 100 30 RDM 30 49 38 44 / 70 0 90 50 LGD 36 47 38 44 / 70 0 60 100 GCD 36 46 38 45 / 90 0 80 100 DLS 39 50 43 50 / 50 0 100 60 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. && $$ SHORT TERM...77 LONG TERM....74 AVIATION...74

373 FXUS65 KREV 222029 AFDREV Area Forecast Discussion National Weather Service Reno NV 1229 PM PST Sun Dec 22 2024 .SYNOPSIS... * Light rain showers this evening, otherwise quiet through Monday. * Quick moving storm for Christmas Eve with impacts to travel over the Sierra passes from snow and wet roads in Western Nevada. * Periods of mainly light rain and mountain snow Thursday into next weekend. && .DISCUSSION... * Changes: Winter weather advisories posted in the Sierra for Christmas Eve storm. Potential for lightning and brief higher intensity snow rates has increased. * Generally quiet weather through Monday, except a few light showers this evening with a fast moving short wave aloft. This is a warm airmass so most areas even in the mountains would see liquid precip type. * Christmas Eve continues to showcase the most robust looking storm this week, though it`s a pretty quick mover so only looking at a 6-12 hour period of heavier precip during the day. Fairly dynamic system along with instability will yield moderate-heavy snows above 7000` with a few hours of higher intensity 1-2"/hour rates likely. Thundersnow possible. Snow lines do look to fall into the 5500-6500` range mid to late day, so mountain communities may pick up some snow. Example: NBM at South Lake Tahoe ranges from 1" to 4", as a result of snow-line uncertainties. * Spillover rain into W Nevada on Tuesday with NBM showing anywhere from 25-50% odds of at least 0.25" wetting rain for W Nevada cities. Decreasing concerns for river impacts due to quick movement of the storm, but there will still be rises on Tuesday into early Wednesday. Winds will increase for a period Tuesday, especially ridges and mid-slopes with 700mb flow 40-55 knots but questions about the lower valleys remain with more of a nebulous pressure gradient. As a result, the NBM is showing 30-50% odds of 45+ MPH peak gusts at Reno and Mammoth Airport. * After a cooler and dry Christmas Day, we enter a period of persistent moist onshore flow into the Sierra Thursday into the next weekend. Rain-snow lines initially look to be low enough Thursday for snow impacts to travel in the Sierra, but rise Friday onward, potentially above 8000`. Right now, precip potentials look light-moderate overall, with highest probabilities of IVT above 500 (moderate AR) to our north. Still a wet period for sure in our mountain communities, with on/off showers into W Nevada. Next Sunday has a bump in the 90th percentile QPF in the NBM so perhaps a signal for something more meaningful then. * Per the latest CPC guidance and AR landfall charts, the storm door for more significant Pacific systems seems to close as we head into the first week or so of 2025. -Chris && .AVIATION... * Periods of VFR-MVFR rain showers for most sites tonight, mainly between 03Z-09Z/Mon. Mountain top obscuration possible. * Winds aloft increase enough for LLWS at most terminals tonight. Models showing 30-40 knots at ridge top level. * More appreciable storm moves in Tuesday with higher probability for IFR conditions in the Sierra and even into W Nevada (RNO), mainly between 12Z/Tue-00Z/Wed. Rain to snow transition at mountain airfields (TRK,TVL,MMH). 10-25% odds of 2" snowfall at TRK/MMH with 55% at TVL. All rain at RNO. Increased winds with 40% odds of seeing S/SW gusts over 35 knots during the daytime Tuesday as ridgetop flow hits 40-55 knots. It`ll be bumpy. -Chris && .REV Watches/Warnings/Advisories... NV...Winter Weather Advisory from 7 AM to 7 PM PST Tuesday NVZ002. CA...Winter Weather Advisory from 7 AM to 7 PM PST Tuesday CAZ071>073. && $$

146 FXUS66 KSTO 222131 AFDSTO Area Forecast Discussion National Weather Service Sacramento CA 131 PM PST Sun Dec 22 2024 .SYNOPSIS... Periodic chances for precipitation and breezy to gusty southerly winds are expected to continue into the week ahead as a series of weather systems impacts the region. .DISCUSSION... Current GOES-West satellite imagery shows a fairly robust swath of low level cloud cover and mid to high level clouds streaming toward interior NorCal this afternoon. While resultant radar imagery generally depicts a lack of attendant precipitation at this time, some returns are beginning to pop up across Shasta and Tehama counties as the next wave of precipitation approaches. Prior to that though, some patchy fog development will be possible ahead of the precipitation this evening. Additional fog development, likely more dense than the evening fog, is then expected into Monday morning following the burst of evening and overnight precipitation. The progressive nature of this wave alongside snow levels generally above 7000 feet are expected to limit overall impacts from precipitation. Current forecast precipitation totals through Monday morning sit around 0.25 to 0.5 inches across the Valley and foothills, with 0.5 to 1.5 inches possible along the Sierra/southern Cascades. Given high snow levels, most accumulating snowfall is expected above pass level with this wave. A slightly more pronounced lull between waves is then expected for much of Monday, before precipitation chances begin to increase again from north to south late Monday into Tuesday. The next wave is expected to be stronger, colder, and wetter than previous waves over the weekend, with a more defined southerly track expected with this system. As a result, higher precipitation totals look to accompany rapidly falling snow levels on Tuesday, which will likely introduce some holiday travel impacts to the region throughout Tuesday. Additionally, breezy to gusty southerly winds (Low elevations: 20 to 30 mph and Along the Sierra: 40 to 50 mph) and isolated thunderstorm potential (10% to 20%) are anticipated as the system moves in as well. Current probabilities of exceeding 0.5 inches of liquid precipitation are around 60% to 90% for much of the Delta, Valley, and lower foothills, with 70% to 95% probabilities of exceeding 1 inch across the Sierra/southern Cascades and northern Sacramento Valley and surrounding terrain. Snow levels are expected to rapidly decrease into Tuesday, sitting near 6000 to 7000 feet on Tuesday morning, before falling to 5000 to 6000 feet by Tuesday afternoon. As a result, the majority of accumulating snowfall is expected above 6000 feet, with generally 60% to 90% probabilities of exceeding 6 inches of snowfall through Tuesday evening. As quickly as this more potent wave arrives, precipitation chances are expected to rapidly drop off Tuesday night, with overall dry conditions anticipated for much of Wednesday (Christmas Day). With a drier period expected to follow, additional chances for fog development will likely be possible, but there is currently some uncertainty with respect to that at the moment. Otherwise, near normal temperatures and light winds are primarily expected for the holiday. Please continue to check weather.gov/sto for the latest updates and check quickmap.gov.ca.us before you go this holiday season! .EXTENDED DISCUSSION (Thursday THROUGH Sunday)... Persistently active weather is expected to continue through at least the end of the week, with latest ensemble trends indicating a continuation of periodic precipitation chances into next weekend. Overall uncertainty does notably increase through the weekend, with ridging aloft attempting to build in from the south, but ensembles differ on how this and additional shortwave ejections will interact late in the extended forecast period. While the Thursday into Friday wave of precipitation looks to follow a similar trajectory to the Tuesday system, ensemble guidance currently indicates a slightly weaker synoptic look to it. As a result, probabilities of liquid precipitation exceeding 0.5 inches around 40% to 60% favor the Delta and southern Sacramento and northern San Joaquin Valleys, while probabilities of exceeding 1 inch around 60% to 90% favor the northern Sacramento Valley and surrounding terrain and northern Sierra/southern Cascades from Interstate 80 northward. Initial snow levels around 4500 to 5500 feet late Wednesday/early Thursday do look to increase closer to 5500 to 6500 feet from midday Thursday into Friday. Resultant probabilities of snowfall exceeding 6 inches above 6000 feet through Friday evening sit around 40% to 70% at this time. Please continue to check weather.gov/sto for the latest updates and check quickmap.gov.ca.us before you go this holiday season! && .AVIATION... MVFR/IFR/LIFR in low cigs through 00z, with precipitation chances increasing from north to south between 00z and 09z. Snow levels remain 6500-7500 feet. Additional visibility reductions in BR/FG then anticipated following precipitation, generally after 09z. Light southerly winds less than 12 kts expected next 24 hours, although some gusts to 30 kts possible along Sierra crest through 12z. && .STO WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory from 7 AM to 7 PM PST Tuesday for West Slope Northern Sierra Nevada-Western Plumas County/Lassen Park. && $$

620 FXUS65 KMSO 221922 AFDMSO Area Forecast Discussion National Weather Service Missoula MT 1222 PM MST Sun Dec 22 2024 .DISCUSSION... KEY MESSAGES: - Risk for pockets of freezing rain Monday morning for valleys below 4000 feet, mainly affecting western Montana. - Pattern will remain active through the week, with mountainous terrain receiving persistent snow, affecting travel over mountain passes. The next week`s worth of weather will be one weak weather disturbance after another, causing a mixed bag of precipitation for valleys generally below 4000 feet. Tonight will be another round of such precipitation, predominantly affecting western Montana valleys below 4000 feet with a rain/snow mix and pockets of freezing rain through Monday morning. Fog and/or low stratus will also be a concern across all of north central Idaho into western Montana tomorrow morning, which will dissipate by late morning. Despite the fact our region`s valleys are not expected to receive much in the way of new snowfall (thus, not producing the much desired white Christmas many are hoping for), the mountainous terrain will steadily accumulate snowfall throughout the week. There will be a brief break on Tuesday, but the majority of the week will be an active one. The next weather system on Christmas Day will be cold enough to support snow down to many valley floors, but accumulations will be very minor (a trace to a half inch, at most) through Wednesday morning. Thursday into the weekend is when things become more interesting as a more potent weather system moves in from the west. As of now, this system also looks cold enough to produce snow down to valley floors. There is much higher confidence that moderate to heavy snowfall will occur above 4500 feet during a period from late Thursday through Sunday (Dec 29), which could create difficult travel over mountain passes for those traveling during the holiday travel period. The most snowfall looks . For I-90 over Lookout Pass, there is currently an 80% chance of at least 6 inches of snow accumulating by Saturday afternoon, and a 60% probability of one foot of accumulation. Both Lolo Pass and Lost Trail pass show a 65% probability of 6 inches occurring by Saturday afternoon. && .AVIATION...Another incoming weather system will bring the threat for mixed precipitation at most, if not all, aviation terminals through Monday morning, occurring between 23/12Z and 23/17Z, especially for KGPI, KHRF, and KMSO. Precipitation will be accompanied by fog and/or low stratus, causing additional impacts to visibility and ceiling heights. Precipitation will continue through Monday, with any mixed precip changing over to rain before dissipating Monday evening. && .MSO WATCHES/WARNINGS/ADVISORIES... MT...None. ID...None. && $$

269 FXUS65 KBOI 222124 AFDBOI Area Forecast Discussion National Weather Service Boise ID 224 PM MST Sun Dec 22 2024 .SHORT TERM...Tonight through Tuesday night...The next storm system is pushing onto the coast this afternoon and will spread precipitation into the area late this evening and overnight. Lower elevations will be rain with snow levels rising to 5500-6500 feet across e-central Oregon and the w-central ID and up to 6500-7500 feet along the NV border. Mountain valleys, to include McCall will see less than an inch of snow from a wet snow or rain/snow mix, while sites above 6000 feet add 3 to 6 inches. Monday is mostly dry as showers kick east of the area by midday. The lull between storms will bring light winds, clearing skies and temperatures at or above normal. The next storm in line will push across the region Monday night and Tuesday. As with recent storms, the axis of heavier precipitation will angle from Harney County northeastward into the w-central Idaho mountains where a broad 0.25-0.50 inches of liquid is expected. Higher mountains will see amounts of up to an inch of liquid. Snow levels will remain between 5500 ft (northern areas) to 7500 ft (NV border). Generally sites above 6-6.5kft will see another 3-6 inches with up to 10 inches across higher peaks. Tuesday night is dry as we head into a brief break in the storms. The west-east storm track will do little to change out the air mass, thus temperatures remain around 10 degrees above normal through Tuesday. .LONG TERM...Wednesday through Sunday...After brief ridging Wednesday, a strong system will move through Thursday, spreading valley rain and mountain snow throughout the area with snow levels 4000 to 5000 ft MSL. Snow amounts Wed night through Thu night should range from 1 to 2 ft in the highest elevations, with 4 to 8 inches in places like Idaho City and McCall. Another weaker system follows Friday, with yet another, longer-lasting system Saturday through Sunday. Total snowfall in the mountains Friday through Sunday will be 2 to 3.5 ft, with 6 to 10 inches in McCall. Snow levels will rise through the period, initially around 4000 ft MSL, but rising to 5000 ft in Baker County and 7000 ft in far SW Idaho. McCall may switch over to rain Saturday after receiving 6 to 10 inches of snow Friday through early Saturday. Temperatures will be above-normal throughout the extended, with the warmest days expected to be Sat/Sun (around 10 degrees above). There is a very low chance for snow in the Treasure Valley Wed night (20% chance), but even if it occurs, little to now accumulation is expected. && .AVIATION...Mostly VFR. Very light valley rain/mountain snow today, resulting in areas of MVFR/IFR conditions in the mountains. Tonight, widespread valley rain/mountain snow resulting in periods of MVFR/IFR conditions. Snow levels rising to 5500-7000 ft tonight. Mountains frequently obscured. Surface winds: SE-SW 5-15 kt. Winds aloft at 10kft MSL: SW 20-30 kt, becoming W 20-35 kt by 12Z/Mon. KBOI...Low VFR cigs possible today with a 10% chance of rain showers at the terminal. Rain will increase tonight (90%), mainly after 04Z/Mon, with cigs lowering to MVFR (10% chance of IFR). Surface winds light, becoming SE 3-7 kt this afternoon. && .BOI WATCHES/WARNINGS/ADVISORIES... ID...None. OR...None. && $$ www.weather.gov/Boise Interact with us via social media: www.facebook.com/NWSBoise www.twitter.com/NWSBoise SHORT TERM...DG LONG TERM....SP AVIATION.....SP

340 FXUS65 KLKN 222218 AFDLKN Area Forecast Discussion National Weather Service Elko NV 218 PM PST Sun Dec 22 2024 .SYNOPSIS...Active weather persists thru the week as a progressive upper wave pattern takes charge. Greatest opportunity for widespread wetting rains will be on Tuesday and Tuesday night. Otherwise precipitation will be focused across northern Nevada. && .SHORT TERM...Tonight through Monday Night Ongoing light shower activity will continue to exit from west to east early this evening though the pause in activity will be very brief. Another shortwave ejects from a region of persistent deep low pressure situated over southern Alaska. This transient shortwave moves thru the PacNW tonight, skirting northern Nevada. Light valley rain and high mountain snow begin to move back into northern Nevada from the west before midnight in Humboldt County, spreading east thru tonight. Activity generally remains north of the US-50 corridor and accumulations will be light, less than 0.10 of liquid for the valleys, with the higher mountain ranges observing between 0.10 and 0.25+ of liquid. Mountain precipitation comes in the form of snow with an inch or two expected. Snow levels remain higher than 7000 feet. Overnight low temperatures reside in the low 20s to low 30s. Precipitation associated with the shortwave exits the forecast area from west to east Monday with the entire forecast area dry by early afternoon under mostly cloudy skies. Progressive wave pattern brings a transient upper ridge thru the western U.S. Monday night and weather will be relatively quiet aside from increasing southerly winds ahead of the cold front expected to pass on Tuesday. Gusts 15 to 20 mph will be in place by sunrise Tuesday. Temperatures continue to reside 10 to 15 degrees warmer than average and daytime highs will be in the mid 40s to mid 50s with overnight lows in the low 20s to low 30s. && .LONG TERM...Tuesday through next Monday Tuesday dawns with another quick moving upper shortwave trough moving through the region. This system will be a quick hitter, exiting by Wednesday morning, but it will pack a liquid punch which is much needed. Starting like the previous system with a mix of valley rain and higher elevation snows with light to moderate accumulations of both possible through early Christmas morning. Unfortunately, cold air will be lacking and late to the party, limiting any valley changeover to snow limited to the overnight hours Christmas eve into Christmas morning. So Santa may have to deal with favorable icing conditions aloft as he visits the lower and middle Humboldt valley. The good news is that higher elevations above 5600 feet like Ely, Eureka, and Wells it should be all snow for the precipitation type. Accumulations have increased from prior model runs with a 0.10 to 0.25 of rain for the Valleys, a 0.20 to 0.45 of water which includes up to 1 to 3 of snow for the passes and roadway summits, and up to 0.80 of liquid, inducing 3 to 8 of snow for the mountains. There may be a brief window for a white Christmas for Winnemucca, Battle Mountain, and Elko, at least on the grassy surfaces if cooler air mixes in quicker than expected during the overnight into Christmas morning, current probabilities however remain low at 25% to 35%. From mid morning Christmas day to mid morning on Boxing day (26th) there will be another quick break in the action before the long duration event finally begins to influence the region as a strong Pacific upper low ejects a pair of shortwaves for Thursday into Friday and the second for late Saturday into next Monday. The good news is that this system is associated with an atmospheric river which will bring in much needed moisture. That bad news is that considering how the models track with these shortwaves, central NV may miss out with needed precipitation. Models continue to be split with this possibility with the NBM and the GFS favoring only minimal accumulations of rain and snow for central Nevada, while the ECMWF and the CMC (Canadian) favor a more southern track with much higher probabilities of rain and snow. Another issue will be temperature wise with the Pacific nature of this system snow levels will be highly variable and may limit snow accumulations for area below 6500 feet. With these issues in mind total accumulations with these systems for central Nevada total rain and snow amounts run from a trace to 0.05 of water with 1 to 2 of snow in the mountains. Amounts for the northern 1/3 of NV look a lot better overall, for the valleys current trend indicate 0.20 to 0.60 of liquid which will include up to 1 of snow. The Passes and roadway summits will see several changeovers to precipitation type from rain to snow and back again, totals look to run between 0.35 to 0.75 of liquid, which will include about 1 to 4 of snowfall. The mountains (above 7000 feet) look to see mostly snow, but current trends indicate about 0.50 to 1.50 of liquid, which includes a 4 day snowfall of 8 to 24+. Temperatures will start on the warm side Tuesday with highs in the upper 40s to upper 50s and lows in the mid 20s to mid 30s. Wednesday through Friday temperatures tumble a bit in the the upper 20s to low 40s with overnight lows in the upper teens to upper 20s. Next Saturday and Sunday temperatures warm back into the mid 40s to mid 50s with morning lows in the low 20s to low 30s. Winds for the period will be generally out of the west to southwest with speeds peaking at 10 MPH to 25 MPH with gusts up to 35 MPH Tuesday, Thursday, and Saturday. Between those days winds will be weaker at 5 MPH to 15 MPH with gusts up to 25 MPH. && .AVIATION...VFR conditions forecast to persist for the next 24 hours. Low ceilings in the 3000Ft to 7000Ft will continue for all terminals with occasional light rain showers for KELY and KEKO which should end by early morning Monday. This evening through Monday morning VCSH and BR will be possible for KWMC, KBAM, and KTPH. This along with showers may occasionally drop conditions to MVFR levels at times. Look for ceilings to rise after 12Z Monday back above 10kFt as this upper trough exits the area. && .LKN Watches/Warnings/Advisories... None. && $$ 92/98/98