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 15, 2023 was used for initial drought conditions.

WEST REGION: Autumn is a month of transition in the West Region, and there are a variety of climatological changes that occur during autumn (September - November, or SON). The monsoon in the Southwest northward into the Four Corners States is usually on the wane before the end of September, and October-November is typically much drier there. Farther north, in east Montana, climatological precipitation slowly decreases during autumn, and the season as a whole is slightly drier than most other times of the year. In contrast, September and October are relatively dry months in the Pacific Northwest, but the wet season typically begins to ramp up quickly during November. Precipitation also increases climatologically across most of California, but November is typically too early for the wet season to begin in earnest. During the last half of August, a strong moisture surge, abetted by Tropical Storm Hilary, is expected to push into western parts of the Four Corners States, southeastern California, and adjacent Nevada, bringing exceptionally heavy precipitation to much of the climatologically arid region which should improve existing drought conditions. Across other areas of drought in the West - in the southern Rockies and across the northern tier of the region - persistence is expected, with some development in areas with some both antecedent moisture deficits and odds in the September-October-November (SON) outlook favoring subnormal precipitation for September-November. The transitional nature of the autumn, and the difficulty of forecasting the evolution of such transitions, brings some uncertainty into the equation, but in areas where dryness is favored for the season (parts of southern Rockies and the Pacific Northwest), confidence is boosted somewhat.

Forecast confidence is moderate for most of the West Region, but high in southern parts of the Four Corners States where a weak end to the Monsoon is expected and the SON outlook shows odds favoring SON dryness.

HIGH PLAINS REGION: For most of this region - especially the western half of the Great Plains - autumn is a transition toward the driest time of year. The higher elevations in Colorado and Wyoming are the exception, where SON is neither wet nor dry compared to other times of the year. Currently, drought is most severely affecting Kansas and Nebraska, where D2 to D4 conditions are common in central and eastern parts of the region. Other areas of drought (D1 to D2) cover the northern and eastern sections of the Dakotas, and parts of southwestern Colorado. No precipitation is expected over the next seven days in most areas, with totals exceeding 0.5 inch likely limited to western North Dakota and the higher elevations in Colorado. The ensuing week, there are somewhat enhanced chances for above-normal precipitation in most locations, particularly in Colorado and Wyoming, while odds favor drier than normal weather in the eastern half of Kansas. The SON outlook is indeterminate throughout the region, with no tilt of the odds toward wet nor dry conditions. Given the lack of any indication of markedly wet weather during the period, and considering that autumn is slightly drier than spring and summer, drought persistence is slightly favored here during the next three months. Some drought development is expected in southwestern Colorado, an area usually impacted by the southwest monsoon, which is not expected to be particularly productive as it winds down during September.

Forecast confidence in the High Plains region is low to moderate due to the lack of strong indicators toward significantly anomalous precipitation totals.

SOUTH REGION: Drought has expanded and intensified over the past several weeks across much of Texas and Louisiana, where subnormal precipitation has been exacerbated by frequent periods of intense heat, especially near the Gulf Coast. Elsewhere, drought is not nearly as prevalent, with generally moderate drought limited to the Red River Valley and southwestern Mississippi. Over the next week, several tenths of an inch of precipitation is expected in central and south Texas while heavier rains - generally 1 to 2 inches - are forecast along the immediate Gulf Coast. Other areas should expect little, if any, rainfall. For the ensuing week, there is an enhanced chance for below normal precipitation in most areas, and no tilt of the odds toward heavier nor lighter than normal precipitation in areas of drought during autumn (above-normal precipitation is favored in eastern parts of the region, but no drought exists in this area). In addition, above-normal temperatures are expected to continue for the period as a whole, worsening the impacts of any dryness. With the precipitation forecast generally showing a neutral to slightly dry tendencies on most time scales, persistence is the only reasonable forecast in the areas of drought, and some expansion northward is anticipated where antecedent moisture shortfalls have the region already approaching drought status. Additional northward expansion toward the Red River and northern Louisiana is also possible, but recent rainfall totals have been closer to normal there relative to areas farther south, leaving these areas less prone to slipping into drought.

Forecast confidence in the South Region is moderate to high.

MIDWEST REGION: This is one area where drought has been on the wane recently, but large areas of severe to extreme drought still cover parts of the western Great Lakes Region and the Mississippi Valley. The rest of August is forecast to be generally drier than normal, with several tenths of an inch anticipated, at best. For SON as a whole, there are enhanced chances for drier than normal weather across roughly the northern half of the Great Lakes Region, as well as northeastern Minnesota. Elsewhere, the forecast indicates no enhanced chances for anomalous autumn precipitation. As the temperatures gradually decline over the course of the season, impacts in some of the most severely affected areas should ease slightly where the seasonal forecast is unremarkable. To wit, conditions are expected to improve a little in areas of extreme drought (D3), but persistence is expected elsewhere.

Forecast confidence in the Midwest is moderate.

SOUTHEAST REGION: Most of the Southeast is free of drought heading into autumn, with the worst conditions (up to D2) covering part of the western Florida Peninsula. Elsewhere, only small, isolated patches of moderate drought exist in northern and southwestern Virginia, eastern North Carolina, and southern Alabama. Over the next week, heavy rainfall amounts of 3 to 5 inches are anticipated in the western Florida Peninsula, but in other areas, odds generally favor below-normal rainfall. For the autumn season as a whole, there are enhanced chances for above normal rainfall regionwide. Given the recent trend toward improvement and the forecast for substantial rainfall during the next few months, the Southeast Region is expected to be entirely free of drought by the end of November.

Forecast confidence in the Southeast is high.

NORTHEAST REGION: As in areas to the south, there is very little drought to be found in this region. Small patches of moderate drought are restricted to west-central Maryland, far western New York state, and some adjacent areas. For the rest of August, odds slightly favor subnormal rainfall in the areas of drought, and the autumn forecast has no tilt of the odds toward dryness nor wetness. But the recent trend toward diminishing drought, a lack of evidence favoring notable dryness, and the seasonal decline in surface water needs leads to a forecast of removal, and the Northeast is expected to be free of drought by the end of November.

Forecast Confidence in the Northeast is moderate.

ALASKA: The small patches of drought in eastern Alaska should be removed over the next few months given typical autumn precipitation totals, colder weather, and the strong historic tendency of summer drought to be gone by the end of autumn, drought removal is forecast

Forecast Confidence in Alaska is high.

HAWAII: Drought has been expanding in Hawaii recently, and this trend is expected to continue. Outside Kauai, chances for below-normal rainfall are significantly enhanced for autumn. Existing drought in western Oahu, central and western Maui, and the middle of the Big Island should persist or intensify over the course of the season, and with dryness favored over most other parts of the state, drought is forecast to expand across the entire state by the end of autumn except in central and eastern Kauai

Forecast confidence in Hawaii is high.

PUERTO RICO: Moderate to severe drought worsened slightly in Puerto Rico over the past month. Currently, there is low confidence in rainfall forecasts over the next few weeks and months, but with rainfall climatologically increasing for part of autumn, enough is expected to cause some degree of improvement by the end of November.

Forecast confidence in Puerto Rico and the Virgin Islands is low.

U.S. VIRGIN ISLANDS: Drought has been a frequent occurrence for the past few years in the Virgin Islands, and drought covers this area currently. Eastern areas in and around St. John are experiencing moderate drought, but extreme drought (D3) is entrenched farther west in St. Thomas and St. Croix. Currently, there is low confidence in rainfall forecasts over the next few weeks and months, but with rainfall climatologically increasing for part of autumn, enough is expected to cause some degree of improvement by the end of November.

Forecast confidence in Puerto Rico and the Virgin Islands is low.

Forecaster: Rich Tinker

Next Seasonal Drought Outlook issued: September 21, 2023 at 8:30 AM EDT