Tools used in the U.S. Monthly Drought Outlook (MDO) include the Climate Prediction Center (CPC) updated temperature and precipitation outlooks for September, 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 model output, September climatology, and initial conditions such as soil moisture and short-term precipitation anomalies. The U.S. Drought Monitor (USDM) valid on August 23 was used for initial drought conditions. La Niña is strongly favored to continue through September 2022.

Drought conditions covered just over 68 percent of the Western Region as of the August 23 U.S. Drought Monitor, a decrease from almost 94 percent coverage at the beginning of the Summer. Most of the drought reduction has occurred across the Four Corners region, southern Great Basin, and the California deserts due to persistently enhanced monsoonal convection, which has generated localized flash flooding at times. Hot, dry conditions promoted some drought expansion across the northern Intermountain West, while the depiction elsewhere in the Western Region remains relatively unchanged and bleak. Climatological dryness reigns supreme during September outside of the monsoon region, limiting the potential for substantial changes to drought conditions. Monsoon activity typically begins winding down during September, though episodic events such as enhanced southerly flow from East Pacific tropical cyclones can provide opportunities for late season moisture surges.The WPC QPF outlook shows some potential for additional monsoonal moisture, though accumulations are generally quite light. Both the 8-14 day ERF and updated September outlooks depict a slight tilt in the odds towards above-normal precipitation over the Southwest. Given these forecasts, additional drought improvements are possible for southern Arizona and much of New Mexico, though confidence in wholesale improvement is quite low due to the spotty hit and miss nature of monsoonal convection and the decreasing precipitation climatology. Confidence in broader improvement is higher for southeastern New Mexico, where short term precipitation forecasts depict heavier accumulations. No drought development is depicted on the outlook, but hot temperatures at the beginning of the month may promote small degradations across the remainder of the Western Region.

Forecast confidence is high for the Western Region, except for the southern Four Corners states where confidence is low.

While localized convection brought spotty relief to portions of the High Plains, the broader signal across the region has been degradation of drought conditions, with below-average precipitation and periods of hot weather observed during August. During September, precipitation climatology dries out considerably across the Plains as humid Gulf of Mexico airmasses give way to drier continental air. Cooler temperatures, declining sun angle, and crops reaching maturity tend to lessen evapotranspiration rates as well, which decreases the potential for rapid drought onset. During September, an unfavorable pattern of above-average temperatures and below-average precipitation is favored, limiting any potential for drought relief moving into the Autumn months. The late season warmth may aggravate impacts across the region, resulting in drought expansion and intensification despite the declining temperature climatology. The September drought outlook maintains persistence for the existing drought areas, and depicts development in areas already abnormally dry across Nebraska, southeastern South Dakota, and eastern North Dakota.

Forecast confidence is moderate for the High Plains Region.

Drought expanded and intensified across the Southern Region for much of the Summer, but late August brought a sudden and destructive reversal. Widespread excessive rainfall swept across northeastern Texas, which combined with hard, dry soils resulted in significant flash flooding events, including across the highly populated Dallas Fort Worth metropolitan area. Flooding rains quickly shifted east, bringing a deluge to the Gulf Coast states and the lower Mississippi Valley. These rainfall events brought swift reductions in the drought depictions across the Southern Region, but difficulties in assessing groundwater conditions due to flood damage have slowed the USDM response. Less rainfall fell across northern Texas and Oklahoma, resulting in a persistence of drought conditions. During the first week of September, widespread heavy rainfall is expected to continue across Texas and the western Gulf Coast, with portions of central Texas that missed out on the initial rainfall event forecasted to receive several inches of rain over the next 7 days. Based on these short term forecasts, there is high confidence for continued drought reduction across most of the Southern Region, except for north Texas and western Oklahoma, which may again miss out on the heavier rainfall.

Forecast confidence is moderate to high for the Southern Region.

Hot, dry conditions during the Summer resulted in areas of drought developing in multiple locations across the Midwest Region, with the greatest concentration of drought areas west of the Mississippi River. During the past few weeks, convection brought localized relief, particularly to the upper Mississippi Valley, but was insufficient to promote widespread drought reduction across the region. During the first week of September, light precipitation is favored across Iowa, extending northeastward to the upper Great Lakes region. This rainfall will likely be insufficient to promote meaningful drought improvements. The updated CPC September outlook favors above-average temperatures across the Midwest Region, which would keep evapotranspiration rates higher than normal. Below-average precipitation is favored for the western Corn Belt, upper Midwest, and northern Michigan. Despite the unfavorable pattern, a cooling climatology during September makes widespread drought development less likely. Some development is possible, however, across southern Iowa, where initial conditions are quite dry and the probabilities for above-average temperatures and below-average precipitation are the highest.

Forecast confidence is moderate for the Midwest Region.

Generous summer convection nearly eliminated drought conditions across the Southeastern Region, but small pockets of moderate drought (D1) remain across the upland region of South Carolina. The piedmont region of South Carolina and coastal Plain regions of North Carolina through the Virginia tidewater and lower Delmarva Peninsula have missed out on the heavier convection in recent weeks, resulting in an expansion of moderate drought (D1) depicted on the August 23 USDM. Additionally, a fairly lackluster seabreeze convection regime across Florida for much of the Summer, coupled with the convergence zone generally favoring the western side of the peninsula resulted in an unusual wet season drought developing along the Space Coast. During the next 7 days, widespread precipitation is favored for Georgia and Alabama, but lighter amounts are expected across the Carolinas. Coupled with enhanced chances for above-average temperatures, drought development is possible across the Carolinas and southeastern Virginia. The updated September outlooks favor wetness for the Gulf Coast states while maintaining equal chances for below-, near-, and above-normal precipitation across the southern Atlantic states. In the absence of a clear wet signal, any drought that develops across the Carolinas or southeastern Virginia during the early part of September may persist through the end of the month. Confidence is quite low for this forecast due to the possibility of tropical cyclone activity during the peak of the Atlantic hurricane season; however, dynamical models do not favor tropical cyclone activity across the Southeast for the upcoming two weeks. Drought improvements seem more likely to occur in Florida, as the seabreeze convective regime has begun to increase in intensity in recent days.

Forecast confidence is low for the Southeastern Region.

Drought conditions remain entrenched across much of the Northeastern Region, with the worst conditions observed across southeastern New England. Convection has increased during the past week, resulting in modest improvements, but drought degradations occurred in regions where rain did not fall, due in part to much above average temperatures. Streamflow conditions remain quite low across the region, with groundwater impacts resulting in widespread water usage restrictions. While some rain is forecast over the next 7-days, accumulations depicted on the WPC QPF outlook are meager, and unlikely to change the increasingly long term drought conditions. Near to below-average rainfall is indicated on the CPC 8-14 day ERF, and below-average rainfall is favored on the updated September outlook. Based on these outlooks, drought persistence is the most likely outcome. While additional development is possible, particularly across northeastern Pennsylvania and the Hudson Valley, the short term precipitation may help maintain a status quo, and evapotranspiration rates decrease fairly rapidly during September. Drought development is anticipated for parts of Delaware, eastern Maryland, and the Delmarva peninsula, where 30-day deficits are quite high.

Forecast confidence is low to moderate for the Northeastern Region.

No drought is currently depicted for Alaska, and drought development is not anticipated as evapotranspiration rates decrease rapidly along with the sun angle. Strong La Niña conditions persist across the Pacific, yielding a pronounced dry signal across Hawaii that is favored to continue through September. Drought conditions have steadily expanded across Hawaii through the Summer, and this trend is favored to continue, with drought possibly enveloping the entire state by the end of the month. Drought conditions have gradually eased across Puerto Rico throughout the Summer, and a fairly generous precipitation climatology coupled with the peak of the Atlantic hurricane season favors continued drought reductions..

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

Forecaster: Adam Allgood

Next Monthly Drought Outlook Issued: September 30, 2022