Tools used in the U.S. Monthly Drought Outlook (MDO) included the Climate Prediction Center (CPC) updated temperature and precipitation outlooks for January, 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), the Week 3-4 outlooks and tools from CPC, dynamical models at the monthly time scale, the 384-hour total precipitation forecasts from several runs of the GFS, and climatology for January, with the December 31 U.S. Drought Monitor used for current drought conditions. Recent precipitation deficits and surpluses were also considered. La Niña conditions are present in late December, and are likely (~95%) to continue through the Northern Hemisphere winter, and into spring 2021 (~50% during April-June).
During December, early season Pacific moisture brought rain and mountain snow across the Northwest, resulting in some modest improvements to drought conditions across Washington, Oregon, northern Idaho, and Montana. A late-month storm is ongoing and bringing additional precipitation to the region, forecast accumulations based on the WPC 7-day QPF are generally more than 3.0 inches liquid equivalent along the coast and at higher elevations. Beyond the near term storminess, a wetter pattern is favored for the Pacific Northwest and northern California from Week-1 to a month, which will bring additional relief during January. Therefore, one class drought improvement is the favored outcome. Although the updated monthly outlook calls for increased chances of above normal precipitation for a larger area of California and the Great Basin, widespread persistence is most likely on a monthly time scale. Persistence is likely for the worst drought conditions throughout the Southwest.
For the Western Region, forecast confidence is moderate for the Southwest, and moderate to high for the coastal areas and Pacific Northwest.
A narrow band of heavy precipitation during December brought some drought relief to southwest Kansas, while drought conditions persisted across the Dakotas. Elsewhere, little change to the drought depiction occurred over the previous four weeks. January is a dry time of year for the High Plains, with colder temperatures gradually causing soils and streams to freeze. Given its a dry time of year, persistence is most likely for much of the High Plains region.
Forecast confidence is moderate to high for the High Plains Region.
Earlier in December, widespread drought expansion and intensification occurred across Texas and parts of the lower Mississippi River basin. At the end of the month, however, widespread rainfall occurred across eastern Texas, Louisiana, and the western Gulf Coast, with amounts of more than 2 inches in some locations. Once this moisture absorbs into the soil and runs off into streams and rivers, it is expected to bring relief to the newly developed short term drought conditions. Improvement or removal of D1 (moderate drought) are indicated where recent rainfall totals exceeded 2 inches. Additional heavy rainfall is anticipated across the western Gulf Coast during Week-1 and a wetter pattern is favored for January. Therefore, drought improvement or removal is forecast for eastern Texas and the lower Mississippi Valley along with southeast Oklahoma. Persistence is likely farther to the west due in part to a drier climatology. The Southeast is expected to remain drought-free through the end of January due to recent wetness and increased chances of above normal precipitation during the next month. Given the ongoing La Niña conditions, drought development as indicated on the seasonal outlook may still occur by the end of March.
Forecast confidence is moderate for the Southern and Southeastern Regions.
A major winter storm brought widespread precipitation (0.5 to 1.5 inches, liquid equivalent) from northern Missouri and southern Iowa east to Illinois and Indiana during the final week of December. The updated January outlook favors above normal precipitation for the Midwest Region. Therefore, drought improvement or removal is indicated on this outlook for existing drought areas.
Forecast confidence is moderate for the Midwest Region.
During December, periodic storminess across the Northeast brought gradual drought relief to most areas. During late December, much of this region received more than 2 inches (liquid equivalent) of precipitation which resulted in a 1-category improvement to lingering drought areas in Pennsylvania, New York, southern New Hampshire, and Maine. Additional storminess is expected during early to mid-January and the updated monthly outlook favors above normal precipitation. Therefore, continued drought removal is likely.
Forecast confidence is high for the Northeast Region.
No drought is currently depicted or anticipated to develop across Alaska for January. January is the dry season for Puerto Rico and no wet signal is forecast. Therefore, drought persistence is likely for the small areas of drought. For Hawaii, La Niña conditions typically result in enhanced trade winds, which increase the potential for drought relief across the leeward sides of the islands. Dynamical model forecasts show the potential for drought relief across the Islands. Based on these factors and it is the rainy season, drought improvement or removal is forecast.
Forecast confidence is moderate for Hawaii and Purto Rico, and high for Alaska.
Forecaster: Yun Fan
Next Monthly Outlook issued: January 31, 2021 at 3 PM EST