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Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
1227 AM EST Sun Dec 22 2024

Valid 12Z Sun Dec 22 2024 - 12Z Tue Dec 24 2024

...Periods of moderate to heavy rainfall for the Pacific Northwest
and northern California as systems move in from the North
Pacific... 
 
...Record warmth possible across parts of the Southwest on
Sunday... 

...More winter weather from the northern Plains through the Great
Lakes and the Northeast from Sunday into Tuesday morning...
 
The general flow pattern becomes more zonal with time, with
systems of Pacific origen moving eastward and reforming downstream
across the Plains/Midwest. The consequence of this pattern will be
rainfall/elevation snows near the Pacific Northwest & northern
California, decreasing warmth across the West, and by Monday
decreasing cold across portions of the East.  Starting out West,
weakening fronts move eastward out of the Pacific into the Great
Basin, pushing batches of rainfall into and through the Pacific
Northwest, northern Intermountain West, and northern California,
with snowfall expected at higher elevations through Tuesday
morning.  The heaviest precipitation is expected in and near
northern California Monday night and Tuesday, which carries some
risk of excessive rainfall/flash flooding, particularly in burn
scars.  Some periods of high winds are expected on Sunday -- wind
advisories are in effect for areas of northern California and
southern Oregon.  Across the Southwest, high temperatures should
rise 60s to 70s on Sunday, threatening daily record high
temperatures in and near southern Arizona and southern California.
 As one of the Pacific disturbances aloft moves east of the
Rockies, a low pressure system develops across the Upper Midwest
and Great Lakes Sunday into early Monday, which is expected to
bring freezing rain to portions of northeast Montana and northwest
North Dakota -- winter weather advisories are in effect -- then
snowfall which increases in coverage and intensity with time from
North Dakota eastward through Michigan into the Northeast.  This
system should weaken as it moves through the Northeast.

A seasonably strong and cold high pressure system migrates through
the East into the Western Atlantic on Sunday and Monday,
continuing the cold in the eastern United States.  Cold Weather
Advisories are in effect across portions of eastern Upstate New
York and northeast Pennsylvania, while freeze warnings and frost
advisories are out for portions of southeast Georgia and North
Florida for Sunday morning.  As the flow over the Great Lakes
becomes more anticyclonic with time, Lake Effect Snows should
continue to fade on Sunday.  For some areas of the East, Sunday
should be the coldest day thus far this winter.  Once the high
moves offshore on Monday, temperatures should begin to moderate
closer to late December averages.
 
Roth 


Graphics available at
https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php