During the past month, increased storminess across the West brought some limited drought relief, though long term drought conditions continue to blanket nearly 94 percent of the Western Climate Region. A mid-December series of storms has started to erode the snowpack deficits across the Cascades and Sierra Nevadas, and further storminess through the end of December may help to erode some of the most severe drought conditions.
In contrast, drought and abnormal dryness expanded considerably across the south-central U.S. and the Southeast, as persistent ridging promoted dry conditions and above-average temperatures.
During the first three months of 2022 (JFM), the pattern across North America is likely to be strongly influenced by ongoing La Niña conditions, which typically favor an active pattern and below-normal temperatures across the Northwest and north-central CONUS, and abnormally dry, warm conditions across the southern tier of states.
The CPC January and JFM temperature and precipitation outlooks broadly reflect this signal, with a potential for the dry signal typically observed across California being suppressed further south than it is during typical La Niña events.
Therefore, drought improvement is favored for much of coastal central and northern California and the Sierra Nevadas, while persistence is maintained across the San Joaquin Valley which relies more on Spring snowmelt for moisture. Mid-December through the end of March is a wet time of year for California which also supports improvement.
Drought improvement is also favored for the Northwest, northern Rockies, the upper Midwest, and New England, while seasonable dryness and cold favor persistence of existing drought areas across the High Plains.
Across the southern tier, additional drought expansion is favored for the interior Southwest and much of Texas, while short term wetness may spark some improvements across the lower Mississippi Valley. Widespread drought development is likely across the Southeast, with drought conditions possibly sneaking northward into the mid-Atlantic despite seasonably low moisture requirements.
No drought is currently present or forecast to develop across Alaska, while enhanced trade winds and periodic troughing associated with La Niña conditions favors drought reductions for Hawaii. Drought conditions have been slowly expanding across Puerto Rico, and this trend is favored to continue through the end of March.
Forecast confidence is high for the interior Southwest, and moderate for California, the Great Basin, and the Northwest.
- Through early December, drought conditions eased a bit across parts of the Northwest and north-central California, but overall protracted moderate to extreme drought remained entrenched across the Western Region, with nearly 94 percent of the region continuing to experience drought conditions as of the December 7th USDM.
- Following up on a potent Atmospheric River (AR) event in November that brought impressive precipitation accumulations but failed to make a substantial dent in the long term drought conditions, several storm systems have impacted the West during December, as a strongly negative Pacific North America (PNA) pattern favored troughing over the West and a storm track further south than is typical during La Niña winter seasons.
- Following a series of storms in mid-December, California’s overall SWE content jumped from 19 percent of normal on December 10th to 76 percent of normal on December 17th. The heavy rainfall and mountain snows have caused flooding and mudslide impacts across the Pacific coastal states as well.
- The stormy pattern is favored to continue during the next week, with up to 3 feet of additional snow possible across both the Sierras and the coastal ranges of north-central California, and 3-4 inches of rain along the coast north of the Bay Area.
- Based on the CPC 6-10 and 8-14 day outlooks, a wet pattern is favored for the remainder of December as well. Despite the ongoing La Niña pattern, the CPC JFM seasonal outlook maintains equal chances for below-, near-, and above-median precipitation for much of California and enhanced chances for above-median precipitation across much of the Northwest.
- Enhanced chances for below-median precipitation are limited to the southern third of California eastward across southern Utah, Arizona, and New Mexico.
- Based on high climatological precipitation, the wet short and medium range outlooks, and recently improved incipient conditions, drought improvements are forecast for coastal California north of the Los Angeles metro area as well as the Sierras.
- Improvements to long term drought conditions are less likely across the San Joaquin Valley region, as this area is more dependent on Spring snowmelt that would occur mainly beyond the JFM period.
- In addition to Pacific moisture, upslope snow events during arctic airmass intrusions into the central US may promote drought improvements across the northern Rockies. In contrast, dry conditions favored under the ongoing La Niña regime favor drought persistence and expansion across Arizona and New Mexico.
Forecast confidence is moderate to high for the High Plains Region.
- Widespread drought conditions persisted and expanded slightly across the High Plains region during the past month, with just over 65 percent of the region experiencing drought conditions as of December 7th.
- Unseasonable warmth, lack of snow cover, and dry soil conditions stressed newly planted winter wheat crops, particularly across Wyoming and Colorado.
- During the next 7 days, widespread light snow (up to 0.5 inch liquid equivalent) is forecast to fall across the Dakotas, with mostly dry conditions persisting across the rest of the High Plains.
- The CPC 6-10 and 8-14 day outlooks favor wetness across Colorado, Wyoming, and the Dakotas, which may bring some limited drought relief, while drier conditions are favored for Nebraska and Kansas. Both the CPC January and JFM outlooks maintain equal chances for below-, near-, and above-median precipitation and temperatures across the High Plains region.
- JFM is a cold, dry time of year for the Plains, which both limits the prospects for substantial improvements to the overall drought situation, and also limits the potential for widespread degradations. Therefore, drought persistence seems to be the most likely outcome, with no additional development indicated on the outlook.
Forecast confidence is moderate to high for Texas, and low for central portions of the Southern Region.
- Drought conditions marched steadily eastward across the Southern Region under a regime of subnormal precipitation and above-normal temperatures, with widespread 1- to 2-category degradations on the USDM depiction over the 4 weeks ending December 7th across Texas, southern Oklahoma and Arkansas, northern Louisiana, and western Mississippi.
- La Niña composites and long term trends yield a strong warm and dry signal across much of Texas, making additional drought development likely.
- Drought development is unlikely to occur across far southern Texas by the end of March, however, due to recent wet conditions (60-day percent of normal precipitation in excess of 200 percent).
- The dry signal in both La Niña composites and the CPC seasonal guidance is less pronounced across the central Gulf Coast, and with no incipient dryness in place, widespread drought development by the end of March is not likely, but drought development may occur across southeastern Louisiana and southern Mississippi.
- Further north, recent rainfall across Arkansas and the surrounding border states, coupled with additional forecast short term moisture, may result in an area of improved drought conditions.
- This region is fairly close to the tail end of the canonical Ohio Valley storm track that frequently sets up during JFM La Niña events and is favored in the CPC seasonal guidance. Therefore, drought redevelopment later in the JFM period following any short term drought improvements is less likely.
Forecast confidence is moderate for the Midwest Region.
- Across the Midwest region, drought conditions persist across northern Minnesota, parts of Iowa and Wisconsin, and northern Iowa. Drought conditions have eased a bit over the past 4 weeks, though severe to extreme drought conditions remain across the Arrowhead region of Minnesota.
- Over the next 7 days, the WPC QPF forecast shows widespread 1 to 1.5 inches liquid equivalent falling across northern Minnesota, which is a fairly significant shot of moisture this time of year. This precipitation may help to relieve ongoing drought conditions.
- The CPC 8-14 day outlook slightly favors a continuation of above-median precipitation across the northern Midwest region. The CPC seasonal outlook favors above-median precipitation across the Great Lakes and southeastern portions of the Midwest region.
- Based on the short term forecast for Minnesota, and the longer term wet forecasts across the remainder of the Midwest Region, continued easing of drought conditions is the favored outcome.
Forecast confidence is moderate to high for the Southeast Region, and moderate for the Northeast Region.
- Abnormal dryness and drought expanded considerably over the past month across the Southeast, as persistent ridging maintained prolonged warm and dry conditions. Abnormal dryness has also begun to expand into parts of the Mid-Atlantic states, but low evapotranspiration rates and dormant vegetation have kept this expansion slow.
- Streamflow values are well below average across much of the east-central US, with topsoil being a bigger concern across the Southeast.
- While dry conditions are favored to continue across the Mid-Atlantic over the next week, widespread 1 to 1.5 inches of rain are forecast across much of the Southeast. While this rainfall may limit continued short term drought expansion, it is unlikely to counteract the longer term warm and dry signal favored during La Niña events and forecast by the CPC monthly and seasonal outlooks.
- Therefore, continued drought development is favored across the Southeast, including much of Florida. Drought expansion into northern Virginia, southern Maryland, and parts of the Delmarva are also possible.
- In contrast, climatological precipitation across northern New England should be sufficient to continue easing the remaining drought area across western Maine.
Forecast confidence is high for Alaska, high for Hawaii, and moderate for Puerto Rico.
- No drought or abnormal dryness is currently in place across Alaska, and drought is not anticipated to develop during the climatologically dry JFM period, especially with the CPC seasonal outlook favoring below-median temperatures.
- An enhanced trade wind regime coupled with trough intrusions favors continued drought reduction across Hawaii, with the largest reductions likely across the northwestern islands.
- In contrast, drought conditions have expanded across Puerto Rico, and climate anomalies associated with La Niña events favor persistent dryness and continued drought development.