Tools used in the U.S. Monthly Drought Outlook (MDO) included the Climate Prediction Center (CPC) temperature and precipitation outlooks for August, 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 outlooks , the Week 3-4 outlooks and tools from CPC, dynamical models at weekly and monthly time scale, the 384-hour total precipitation forecasts from several runs of the GFS, climatology, and initial conditions such as soil moisture. The U.S. Drought Monitor, valid on July 27 at 12Z, was used for the initial drought conditions.

Drought remains entrenched across most of the region from Montana westward to Washington and southward across Arizona, but robust monsoonal rains have brought some degree of relief to central and southern portions of the Four Corners Region. Localized flooding is possible as far north as southeast Oregon, central Idaho, and southwest Wyoming during the first few days of August, but it looks as though monsoonal rains will ease for most of the first half of August. Storminess could re-intensify later in the month, particularly across Arizona and New Mexico, where additional relief is expected, but the northward extent and duration of abundant rainfall is uncertain. Drought is expected to persist in the central Rockies and Great Basin, although parts of these regions could see some relief depending on how far north adequate rainfall will extend. Farther north and west, drought persistence and intensification is expected with higher confidence given the climatological dryness of the Far West and the enhanced chances for subnormal August precipitation noted in parts of Montana and Wyoming.

Forecast confidence is low to moderate across Utah, Nevada, and adjacent areas, but high for the rest of the Western Region.

Drought (mostly severe to extreme, or D2-D3) is entrenched across the northern Plains, Wyoming, and western Colorado. With the uncertainty in the progress of the monsoon during August, persistence or deterioration is forecast, but with relatively low confidence. Farther east, the drought across the northern Plains should continue or worsen given enhanced chances for subnormal August precipitation. The odds of a dry August also led to a forecast expansion of drought in the central Plains where some moisture deficits already exist. By the end of the month, only eastern Colorado and parts of Kansas are expected to be drought-free. 

Forecast confidence is high across the northern Plains, and moderate in the central Plains and eastern Colorado, and low elsewhere.

Drought continued to recede across the Southern Region in July, with drought limited to small parts of western Texas and northern Oklahoma. With odds favoring a wet August, drought is expected to be removed from western Texas by the end of August, but an uncertain rainfall forecast and enhanced chances for warmer than normal weather led to a low-confidence forecast of drought persistence in northern Oklahoma. The rest of the region should remain drought-free.

Forecast confidence is moderate to high for the Southern Region.

In the Midwest, severe to extreme drought covers most of Minnesota and northern Iowa while moderate drought dominates central and eastern Iowa, southern Wisconsin, and northern Illinois. Odds favor a drier than normal August across most of Minnesota and parts of Iowa, leading to a fairly high confidence persistence forecast there. Farther east, odds favor neither dryness nor wetness in Wisconsin and Illinois, but warmer than normal temperatures and an expected dry start to the month should allow drought to hang on there as well. In the eastern Great Lakes Region, odds favor surplus August precipitation, which should nearly or completely remove the lingering area of drought in eatern Michigan.

Forecast confidence is High in the Upper Mississippi Valley, and moderate for the Midwest Region.

Moderate to severe drought in the Northeast Region is limited to northern New England. August is expected to end up warmer than normal there, but precipitation signals are mixed to say the least. A low confidence forecast of persistence seems the path of least regret, especially given the time of year, with increased demands and soil moisture and groundwater during the height of summer.

Forecast confidence is low for the Northeast Region.

Across the Southeast, only a small area of drought remains in the central Virginias. The August outlook features enhanced chances for above-normal rainfall, which should eliminate this small area of drought.

Forecast confidence is high for the Southeastern Region. 

Odds favor surplus precipitation across Alaska, and subnormal rainfall through most of Hawaii. As a result, the Hawaiian drought should persist or deteriorate, with expansion possible into areas already identified as abnormally dry (D0) on the Drought Monitor. the outlook for Puerto Rico is less certain, but given rainfall trends over the rest of the island recently, there is a low confidence removal forecast there.

Forecast confidence is high for Alaska and Hawaii, and low for Puerto Rico.

Forecaster: Richard Tinker
 
Next Monthly Drought Outlook issued: August 31, 2021 at 3pm EDT