Tools used in the U.S. Seasonal Drought Outlook (SDO) include the Climate Prediction Center (CPC) temperature and precipitation outlooks for September and September-October-November (SON), 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 and seasonal time scale, climatology for SON, and initial conditions such as soil moisture. The U.S. Drought Monitor valid on August 13, 2024 was used for initial drought conditions.

The autumn season (September-November) is climatologically transitional in and near the West Region, with the seasonable dryness (wetness) during summer in the western (central) parts of the contiguous 48 states moving toward the climatologically opposite regimes during winter. Typically, the Pacific Northwest is the first area in the Far West to experience increased precipitation which usually results in net soil moisture recharge during the season. In these regions, extant drought is expected to be improved or removed by the end of November, with confidence boosted in central and western sections of Washington and Oregon, where the autumn long lead forecast (LLF) favors above-normal precipitation. In contrast, drought areas over the rest of the region exist in regions that tend to get at least somewhat drier during the 3-month period, and over central and southern parts of the West Region, the LLF shows enhanced chances for below-normal precipitation and above-normal temperatures. This justifies a forecast of drought persistence where it exists, with some expansion forecast in some southern areas of the West Region. It should be noted that drought is currently not present in a vast majority of California and the Great Basin, and antecedent conditions (especially high reservoir levels) should be sufficient to preclude drought development by the end of November.

Forecast confidence is generally high, but moderate in the Intermountain West due to a lack of precipitation signal in the September-November LLF and the uncertainties inherent to a transitional situation.

In the High Plains Region, autumn climatologically becomes drier as the season progresses. September brings anywhere from 5 to 11 percent of the annual precipitation while November only delivers 2 to 4 percent of the annual total east of the Rockies (somewhat more in western Colorado and Wyoming). In the short-term, moderate rains are forecast in the eastern Dakotas and in some of the higher elevations during the last half of August, with only light amounts anticipated elsewhere. The monthly LLF for September favors warmer and drier than normal conditions everywhere outside North Dakota and northwestern Wyoming while the autumn LLF favors abnormally warm weather regionwide and subnormal precipitation everywhere except the Dakotas and northern Wyoming. The combination of the short-term forecast, the LLFs for autumn and September, and drying climatology favors drought persisting where it exists, with development anticipated across a large part of Kansas, Nebraska, and southern South Dakota.

Forecast confidence is high for most of the High Plains Region, but moderate over the Dakotas and northern Wyoming where the LLF does not favor subnormal precipitation.

September in the South Region is one of the wetter months from central Texas westward, with 15 to 20 percent of the annual total typically falling on the Big Bend and Deep South Texas. Farther east, September is actually a little drier than most months from eastern Texas and southeastern Oklahoma eastward, with most of Arkansas and northern Louisiana typically recording 2 to 5 percent of the annual total during the month. For November, the numbers are similar in eastern parts of the South Region, but over western Oklahoma and the western half of Texas, the month usually brings less than 5 percent of the annual precipitation. In the Big Bend of Texas, less than 2 percent typically falls in November. The LLF for September shows increased chances for above-normal precipitation along the southeastern tier of Texas and southern portions of Louisiana and Mississippi, but totals are expected to be less than normal across western Arkansas, Oklahoma, and the northwestern half of Texas. The seasonal LLF for September-November leans toward drier than normal conditions over most of the South Region except southeastern Texas, southern portions of Louisiana and Mississippi, and most of Tennessee. Both the September and September-November LLFs favor warmer than normal conditions regionwide. Because of the LLFs and climatology, areas of existing drought are expected to persist, with development expected in areas where there is antecedent short-term dryness and where September-November is expected to be drier than normal.

Forecast confidence is High in western parts of the South Region, moderate in the central tier, and low to moderate in Tennessee where the LLFs favor neither wetter nor drier than normal conditions.

Drought in the Midwest Region is restricted to the southeastern two-thirds of Ohio and a few small areas in north-central Kentucky, plus portions of southwestern Missouri. September-November precipitation is expected to be below-normal across Missouri and adjacent portions of Illinois and Iowa, so the drought in southwestern Missouri should persist. Despite some antecedent dryness in other parts of the western Midwest Region, heavy precipitation during the last half of August is expected to preclude development outside a relatively small area adjacent to the existing area of moderate drought. On the east side of the region, drought conditions have been around for a few months now, and with no clear indicators of heavy precipitation in the near future, drought is forecast to persist there. Some drought expansion is possible in the eastern Midwest Region, but with no clear indicators of below-normal precipitation, there is not enough confidence to forecast development in any specific location.

Forecast confidence is moderate Midwest Region.

The Southeast Region has seen a dramatic decline in drought coverage over the past 4 weeks, punctuated by areas of heavy rains from Tropical Storm Debby in early August. Currently, drought is restricted to small parts of western and northern Alabama, a small part of east-central Florida, and the Piedmont and mountainous regions of Virginia. The autumn LLF leans toward wetter than normal conditions east of the spine of the Appalachians and across Florida and the eastern Gulf Coast Region, with neither precipitation extreme favored elsewhere. Warmer than normal weather is expected regionwide, especially across southern Florida and northern Virginia. Climatologically, autumn is slightly drier than other times of the year across Alabama, Georgia, and the adjacent Carolinas, and unremarkable elsewhere. As a result, the drought areas in east-central Florida and the northern half of Virginia are expected to improve. The other patches of drought are outside the forecast area for above-normal precipitation, so with warmer than normal conditions anticipated, drought persistence is expected across western and northern Alabama, and southwestern parts of Virginia. But given the forecast uncertainty, no specific area of development can be identified.

Forecast confidence is low to moderate in the western tier of the region, and high farther east where the LLF favors wetter than normal conditions.

Following the rains from Tropical Storm Debby, drought in the Northeast Region is now limited to western Maryland, most of West Virginia, southwestern Pennsylvania, and southeastern New Hampshire. Most of the Northeast typically experiences an increase in soil moisture during autumn, except in West Virginia and southwestern Pennsylvania, where little or no change occurs during typical years. The autumn LLF leans toward above-normal precipitation east of the Appalachians, with no tilt of the odds elsewhere, including most of West Virginia. These factors support a forecast of drought improvement or removal in southeastern New Hampshire and west-central Maryland, and persistence farther west across most of West Virginia and the Maryland Panhandle. An exception is over part of western West Virginia, where the current extreme drought conditions (D3) should improve slightly to severe drought by the end of November .

Forecast confidence is high east of the Appalachians, and moderate farther west.

Alaska is mostly drought-free with only a small moderate drought area designated for southeastern Alaska. Since above-normal precipitation is favored for September-November, removal is forecast.

Forecast confidence is high for Alaska.

Persistence is forecast for ongoing drought areas of Hawaii, consistent with the LLF for autumn. Drought may expand into central parts of the Big Island, but with the seasonal increase in precipitation during the end of autumn, larger areas of development are not expected.

Forecast confidence is moderate for Hawaii.

Puerto Rico has remained drought-free since late April. Given the antecedent wetness, wet climatology, and the North American Multi-Model Ensemble favoring above-normal precipitation, development is unlikely through the end of November.

Forecast confidence is high for Puerto Rico.

Similar to neighboring Puerto Rico and for the same reasons, the U.S. Virgin Islands are likely to remain drought-free through the end of November.

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

Forecaster: Rich Tinker

Next Seasonal Drought Outlook issued: September 19, 2024 at 8:30 AM EDT