Tools used in the U.S. Monthly Drought Outlook (MDO) include the Climate Prediction Center (CPC) temperature and precipitation outlooks for December, various short- and medium-range forecasts and models such as the 7-day quantitative precipitation forecast (QPF) totals from the Weather Prediction Center (WPC), the 6-10 day and 8-14 day CPC extended-range forecasts (ERFs), dynamical models at the monthly time scale, climatology for December, and initial conditions such as soil moisture. The U.S. Drought Monitor (USDM) valid on November 26, 2024 was used for initial drought conditions. There is a 57% chance of La Niña conditions developing by the end of December. As such, potential effects from La Niña are only weakly considered in this outlook.



Snowpack is running near to above normal across much of the Western region at the start of December, the exception being parts of the Southwest and eastern portions of the central and northern Rockies. Soil moisture is also in predominantly good shape throughout much of the West. However, the top 50 to 100 cm of soil have dried out quite a bit during November, especially in the central and northern Rockies and Desert Southwest. Looking ahead to December, drought persistence is forecast throughout much of the Intermountain West, associated with warmer and drier than average temperature and precipitation outlooks, respectively, favored through at least mid-December. Where the highest chances of warmer and drier conditions are favored across the Desert Southwest, and where soil moisture conditions are worse off, some drought development is forecast. Conversely, drought removal and improvement are forecast for remaining moderate drought (D1, as depicted in the USDM) in the northern Cascades and severe to exceptional drought (D2-D4) areas in the northern Rockies, associated with near to above average precipitation outlooks, with above average chances expanding in spatial coverage toward the latter half of the month.



Forecast confidence is high in the Western region.



In the High Plains region, drought persistence is predominantly favored, associated with a dry time of year, mixed temperature signals in the short and medium-range outlooks, and near to above average precipitation signals. Some of the wetter than average chances in the short-range precipitation outlooks in the Northern Plains are primarily driven by a low precipitation climatology, as December is a very dry time of year, so even light precipitation amounts are enough to push odds toward above average precipitation when that occurs. As such, despite the wetter than average signals across some of those areas in the Northern Plains, drought persistence is favored. In western portions of the High Plains region, drought improvement and removal are favored, associated with elevated odds of precipitation in areas with higher precipitation climatologies than the aforementioned areas in the Plains. Also, there is a possibility of the mean synoptic pattern retrograding toward the latter half of December. This may result in increased troughing across central North America and potentially increase precipitation chances due to upslope flow for eastern portions of the central and northern Rockies, if cold air dives southward from Canada and along the Front Range. The small area of drought removal forecast in southeastern Kansas is associated with heavy precipitation during November, especially early on, and residual improvements as drought indicators continue to respond.



Forecast confidence is moderate to high in the High Plains region.



By the end of December, drought persistence is favored across western Texas, parts of Mississippi, and the Tennessee Valley in the Southern region. This persistence is associated with near to warmer than average temperatures forecast and precipitation signals either lacking entirely (Tennessee Valley and Mississippi) or precipitation chances leaning below average (western Texas) during December. Across the remainder of the Southern Plains, drought removal and improvement are favored. In southern and eastern Texas and the Lower Mississippi Valley, much of the improvements forecast are associated with above average precipitation chances throughout December. However, farther northward across the Ark-La-Tex, Oklahoma, and the Ozarks, much of the removal is due in large part to the heavy precipitation amounts received during November and the potential for residual improvements as drought indicators continue to respond early on in December. However, there is some indication that the mean troughing over the western Atlantic Ocean may retrograde a bit toward the latter half of December, which could result in a more active pattern and increased precipitation chances again across these areas.



Forecast confidence is moderate in the Southern region.



Drought persistence is favored for much of the Midwestern region, the exception being southwestern Missouri, central parts of Michigan's Upper Peninsula (UP), and parts of the Upper Ohio River Valley. The forecast drought removal in southwestern Missouri is associated with heavy precipitation during November and the potential for drought indicators to continue to respond early on in December. The targeted areas of improvement in the UP of Michigan and the Upper Ohio Valley are associated with a synoptic flow pattern that favors increased chances of lake effect snow in areas that have experienced marked improvements to soil moisture over the last 30 days.



Forecast confidence is moderate in the Midwestern region.



In the Southeastern region, drought is favored to persist through the end of December, as drier than average precipitation is favored by the end of the month. For parts of Florida and northern South Carolina that are currently depicted in abnormal dryness (D0, as depicted in the USDM), and where soil moisture signals are driest, drought development is favored. There is some uncertainty along the Gulf Coast, associated with above average precipitation chances early on in December and the potential for the synoptic flow pattern to retrograde westward toward the latter half of December, which could possibly increase precipitation chances again.



Forecast confidence is low in the Southeastern region.



There have been some improvements in the topsoil moisture during November across the central and northern Appalachians, the coastal Mid-Atlantic, and New England in the Northeastern region. However, drought persistence is broadly favored in these areas by the end of December, associated with a predominantly cold and dry pattern forecast through at least the middle of the month. On the other hand, the synoptic flow pattern is favorable for lake effect snow, which could result in some drought removal and improvement downwind of Lake Erie and along the windward side of the Allegheny Front in areas that have seen improvements in soil moisture in recent weeks.



Forecast confidence is moderate in the Northeastern region.



In Alaska, abnormal dryness (D0, as depicted in the USDM) was removed from southern parts of the Panhandle since the November release of the MDO, due to heavy precipitation. Given the time of year and wet precipitation outlook through the end of December, Alaska is forecast to remain drought-free.



Forecast confidence is high in Alaska.



Drought persistence is favored throughout the Hawaiian Islands. Stream flows continue to struggle a bit, despite some improvements to drought conditions over the past 30 days. In addition, near average precipitation is favored through mid-December, with signals lacking for the month as a whole, according to the North American Multi-model Ensemble (NMME). However, this is offset by December being a climatologically wetter time of year for Hawaii, hence the persistence forecast.



Forecast confidence is moderate in Hawaii.



Despite a dry end to November in Puerto Rico, many locations experienced near to above average precipitation for the month as whole, particularly across eastern and extreme western parts of the island. Given good antecedent conditions and favorable December precipitation outlooks from the NMME, drought-free conditions are favored to persist through the end of December.



Forecast confidence is high in Puerto Rico.



November was very wet in the U.S. Virgin Islands (USVI), with the islands experiencing nearly twice their average rainfall. Groundwater levels are also in good shape, due in part to the above average November rainfall. Looking ahead to December, above average precipitation is also favored, which will likely keep the USVI free from drought by the end of the month.



Forecast confidence is high in the U.S. Virgin Islands.



Forecaster: Adam Hartman



Next Monthly Drought Outlook issued: December 31, 2024 at 3:00 PM EST