La Niña conditions have developed and are expected to continue with an 87% chance during the Northern Hemisphere winter 2021-22.
Drought continued across much of the western and north-central CONUS and there was some improvement across parts of northern California, western Nevada, the Pacific Northwest, the Southwest and the Rockies due to below-normal temperatures and above-normal precipitation during October.
However, there was some deteriorating drought conditions across portions of western Montana, as the region experienced above-normal temperatures and below normal precipitation.
Parts of the Southern and Central Plains experienced a mix of deteriorating drought conditions with some rapid drought re-development in areas previously in drought earlier this year due to above-normal temperatures and below-normal precipitation during October, while drought conditions in most of the Northern Plains have improved, as some heavier precipitation amounts have resulted in improved soil moisture and stream flows.
Improvements have also been observed across parts of the western, central and southern Midwest and Great Lakes region in October, while below-normal rainfall and above-normal temperatures have resulted in abnormal dryness (D0) and moderate drought (D1) conditions in north-central Wisconsin in recent weeks.
The Southeast is drought-free across most of the region during October, but some areas along the Atlantic Coast have teetered between abnormal dryness (D0) and moderate drought (D1) conditions in recent weeks.
Drought conditions continued across northern New England, as long-term precipitation deficits and soil moisture depletion are evident.
Looking forward to November, heavy rainfall is predicted across parts of the northwestern CONUS and northern California early in the period, with a wetter pattern also favored through the remainder of the period, which should curtail and reverse the ongoing drought across the above region.
However, persistence is likely elsewhere across the Western and High Plains Regions due to above-normal temperatures and near- to below-normal rainfall during the period. Near- to above-normal precipitation is expected across the Midwest and Northeast early in the period and a similar wetter pattern is favored through the end of November, which should improve the ongoing drought conditions across the regions where above-normal precipitation is favored.
Forecasts call for above-normal precipitation across much of the Southeast early in the period, and near-normal rainfall and temperatures through the end of November. Therefore, the Southeast is likely to remain drought-free, except a small area in eastern North Carolina where the ongoing moderate drought conditions are expected to persist throughout the month.
Time of year and climatology are likely to keep Alaska drought-free through the end of November. Ongoing D1-D3 (moderate-extreme) drought is likely to persist in Hawaii, as seasonal temperatures are expected and the state enters into a climatologically wetter time of year, despite drier signals at the monthly lead.
Drought persistence is likely across portions of southwestern coastal areas of Puerto Rico due to a lack of wet signals and areas heading into their climatological dry seasons.
Forecast confidence is high for the Western Region.
- Drought conditions continue to blanket the Western Region, with 98 percent of these states experiencing moderate drought conditions (D1) or worse, and just under 54 percent of the region in extreme to exceptional drought (D3-D4).
- Parts of the Pacific Northwest and northern California have experienced modest improvements in drought conditions due to recent very heavy rainfall brought by a strong atmospheric river (AR) event. Soil moisture conditions were much improved over the areas, but the received heavy precipitation was not enough to offset the long-term rainfall deficits.
- As the region enters into a climatologically wetter time of year, and short-term to monthly forecasts favor above-normal rainfall over the areas, drought removal (D1) and improvements (D2-D4) are expected to continue in parts of the Pacific Northwest and the northern Rockies.
- However, for the central and southern West Coast, the Great Basin, and Four Corners, any excessive rainfall will likely not be enough to improve drought conditions, as antecedent soil moisture conditions are widespread below the 5th percentile of the climatological distribution (below the 20th percentile across the Four Corners), stream flows have begun to decline in recent weeks as the Southwest Monsoon Season has come to an end, and major reservoirs remain at record low levels.
- Short-term to monthly forecasts favor near- to below-normal precipitation and near- to above-normal temperatures over the region. As such, drought persistence is favored for the remainder of the Western Region, as these areas will require sustained above-normal precipitation for several weeks for meaningful improvements.
Forecast confidence is moderate-to-high for the High Plains Region.
- Across the High Plains region, drought is also prevalent, with nearly 63 percent of the region currently experiencing moderate drought (D1) conditions or worse.
- Much of the Dakotas have experienced improving drought conditions in recent weeks, with many locations receiving 2 to 5 inches above-normal precipitation.
- Large areas of near- to above-normal precipitation also extend westward to Wyoming and southward to Kansas. This has resulted in marked improvements to soil moisture conditions across much of the region.
- However, east-central Colorado experienced 1 to 2 inch precipitation deficits in October, forcing drought expansion or redevelopment over these areas.
- As the High Plains Region enters into a climatologically drier season, and with the lack of wet signals in short-term forecasts and extended range to monthly forecasts favoring near- to below-normal precipitation and near- to above-normal temperatures across the region, drought persistence is expected in much of the region.
- Some drought development is also likely over some abnormally dry (D0) areas of Colorado and Kansas.
Forecast confidence is moderate for the Midwest Region.
- The western and central Midwest has benefited in recent weeks from 1 to 5 inches above-normal rainfall and improved soil moisture, which has led to improving drought conditions, mainly for parts of Minnesota, much of Iowa, parts of Wisconsin, Illinois and Indiana.
- However, long-term deficits remain widespread across northern Minnesota and the western Corn Belt. North-central Wisconsin and adjacent Michigan also experienced abnormal dryness and some drought development due to 1 to 3 inch rainfall deficits.
- Temperatures typically become less of a factor as the Midwest enters its cold season, particularly the northernmost areas.
- During November, near- to above-normal precipitation odds are favored for the Midwest Region, with 1 to 4 inches of rainfall received in recent days across most of the region.
- Areas of removal (D1) and improvement (D2-D3) are mainly designated to areas that have experienced improved soil moisture conditions in recent weeks. Therefore, drought improvements are forecast across current drought areas in the Midwest.
Forecast confidence is moderate for the Southern Region.
- In the Southern Region, western Texas and the ArkLaTex experienced rapid expansion of drought during October due to 1 to 3 inch rainfall deficits and above-normal temperatures, while much of eastern and central Oklahoma has experienced drought improvement, benefiting from 1 to 4 inch rainfall surpluses across these areas in recent weeks.
- During November, 1 to 2 inches of precipitation in the first week is forecast across eastern Oklahoma and western Arkansas, while extended range (6-14 days) and monthly outlooks favor below-normal precipitation across the Southern region.
- Therefore, drought persistence is expected for the current drought areas in the region and drought development is likely over much of Texas and west-central Oklahoma.
Forecast confidence is moderate for the Southeast Region.
- The Southeast was drought-free most of the time during October. However, some locations across the Carolinas and Virginia have experienced abnormally dry conditions due to 1 to 3 inch rainfall deficits across these areas. Moderate drought developed recently over a small area in eastern North Carolina.
- With near- to below-normal precipitation favored during November, drought persistence is expected for areas in drought over eastern North Carolina and drought development is likely over some abnormally dry (D0) areas in the Carolinas.
Forecast confidence is high for the Northeast Region.
- In the Northeast, moderate (D1) to severe (D2) drought is confined to a small area in northern New England. Healthy streamflows and decent antecedent soil moisture conditions are evident over most of the region.
- Although above-normal temperatures are favored for November, it is less of a factor in increased evaporation rates during the winter season.
- Given the favorable season for soil moisture recharge and above-normal precipitation is favored across the Northeast during November, modest improvement (D2) and removal (D1) of drought are likely in the Northeast.
Forecast confidence is high for Alaska, moderate for Hawaii, and moderate-to-high for Puerto Rico.
- Alaska is drought-free presently and much of the state entered its annual freeze during November. Therefore, Alaska is likely to remain drought-free through November.
- In Hawaii, although the region is entering its climatological wet season, drought persistence is likely, with seasonal temperatures and below-normal precipitation expected.
- Puerto Rico received some beneficial rainfall in recent weeks, which resulted in drought removal across the region. Moderate drought developed in abnormally dry areas near the southwestern coast recently. As the region heads into its climatological dry season and dynamical models favoring below-normal rainfall, drought persistence is likely in existing D1 (moderate drought) areas along the southwestern coast.