Tools used in the U.S. Seasonal Drought Outlook (SDO) included the Climate Prediction Center (CPC) temperature and precipitation outlooks for August and August through October 2021 (ASO), various short- and medium-range forecasts and models such as the 7-day quantitative precipitation forecast (QPF) 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 related tools from CPC, dynamical models at the monthly and seasonal time scales, the 384-hour total precipitation forecasts from several runs of the GFS, climatology for the ASO season, and initial conditions such as soil moisture. The USDM valid on July 13 was used for initial drought conditions. 

Drought remains firmly entrenched across the western conterminous U.S., with nearly the entire Western Region experiencing drought conditions (D1 or worse) according to the US Drought Monitor valid on July 13, 2021. An unprecedented heat wave baked the Northwest in late June, with daytime temperatures climbing near 30 deg. F above normal. New all-time record high temperatures were established at numerous locations, including Seattle WA (108F), Portland OR (116F), and Salem OR (117F). Quillayute, in far western Washington, hit 110F -- more than ten degrees higher than their previous all-time record. In Lytton, British Columbia (about 200 miles northeast of Seattle), temperatures climbed to 121F, easily setting a new all-time high temperature record for Canada. Most areas of Idaho and Montana are now D2-D3, with some D4 in central Idaho. Farther south, conditions are even more extreme, with D3-D4 encompassing large sections of eastern Washington, interior Oregon, California, Nevada, Utah, Arizona, and adjacent western Colorado and western New Mexico. There is good news in the short-term across the Southwest, where monsoon rains should be abundant until about the end of July. Conditions are more uncertain thereafter, and the 3-month ASO outlook favors subnormal precipitation. Late summer is the wettest time of year in this region, and the July moisture should bring drought improvement that will likely not reintensify between August and the end of October. Part of east-central Arizona could record over 4 inhces of rain by July 22. One-third to one-half of the annual precipitation total in Arizona, southern Utah, and New Mexico falls during July through September. Over the rest of the West, annual precipitation totals are not as dominated by the late summer monsoon, and the ASO outlook favors less precipitation than normal everywhere except Washington, north and west Oregon, north Idaho, and adjacent northwest Montana. Above-normal temperatures are expected regionwide. Based on these considerations, drought is expected to persist or intensify outside the desert Southwest, with drought covering the entire region except westernmost Washington by the end of October.

Forecast confidence is high in the West Coast States, where precipitation is climatologically low until autumn, and moderate for the desert Southwest, Utah, Idaho, and Montana.

In the High Plains region, drought is entrenched across northern and western sections (i.e., the Dakotas, Wyoming, and western Colorado) like it is across most of the West Region. In sharp contrast, Nebraska, Kansas, and the eastern half of Colorado contain few areas of drought. Climatologically, ASO as a whole is a drier time of year across Wyoming, but for the rest of the region, precipitation climatologically wanes as August progresses into autumn. The third week of July could bring a couple inches of precipitation to eastern Kansas, but the short-term looks drier elsewhere, and the ASO outlook favors deficient precipitation everywhere but the east half of Kansas and extreme southeastern Nebraska. Drought persistence or intensification is the only reasonable forecast in areas of existing drought, and drought is expected to expand across all of Wyoming, northeastern Colorado, western Nebraska, and adjacent South Dakota by the end of October. Recent surplus precipitation should preclude drought from extending into more of eastern Colorado and Kansas.

Forecast confidence is medium for the High Plains Region.

Precipitation during the last few weeks has almost entirely removed drought from the Southern Region. Only parts of the western Big Bend of Texas and small patches of northwest Oklahoma remain in drought. The monsoonal showers and thunderstorms that should bring some relief to the southern Rockies should also bring improvement to western Texas despite the ASO outlook favoring subnormal precipitation. In Oklahoma, the isolated patches of lingering drought are expected to be removed by the end of October, though with much less confidence.

Forecast confidence in the Southern Region is low to moderate across western Oklahoma, and high elsewhere.

In the areas of drought across the Midwest Region (most of Minnesota, central and northern Iowa, southern Wisconsin, and adjacent locales), the forecast has to weigh short-term wetness against enhanced chances for subnormal ASO precipitation. This inherently makes for an uncertain forecast, but the short-term looks wettest across most of Iowa and points east, which is where some improvement or removal is forecast. Farther north across Minnesota and small parts of adjacent states - where significant precipitation is not expected as July plays out - drought is forecast to persist.

Forecast confidence in the Midwest Region is low.

The Southeast Region is drought-free, and is expected to remain so through the end of October. Only parts of the western Carolinas are experiencing any abnormal dryness. Precipitation looks unremarkable in the short-term, and odds favor surplus precipitation for ASO through most of the region outside the Florida Peninsula. Even there, in the absence of any compelling reason to expect markedly below-normal precipitation, drought development is not expected

Forecast confidence is moderate to high for the Southeastern Region.

In the Northeast Region, drought is restricted to parts of Cape Cod, and from northernmost New York eastward through west-central Maine. With surplus ASO precipitation favored, drought should be on the decline if not removed altogether. The forecast for Cape Cod is less certain, with drier weather expected in the short-term and existing groundwater shortages. But even there, ASO precipitation should bring the region out of drought by the end of the period.  

Forecast confidence is moderate for Cape Cod, and high for the rest of the Northeast Region.

There is some dryness in southern and eastern Alaska, but drought development is not expected there by the end of October. The lingering drought in southern Puerto Rico is expected to dissipate as ASO is the wettest time of year climatologically, and the expected enhanced tropical activity further argues for a forecast of removal. In contrast, ASO is expected to be drier than normal across Hawaii, which should cause drought to persist or intensify, with some expansion expected in the Big Island, O'ahu, and Kaua'i.

Forecast confidence is high in Puerto Rico and Hawaii, and moderate in Alaska.

Forecaster: Rich Tinker
 
Next Seasonal Drought Outlook issued: August 17, 2021 at 8:30am EDT