The southwestern contiguous US (CONUS) and the Southern High Plains experienced worsening drought conditions under predominantly warm and dry conditions since mid-April. Several locations across the Southern Plains experienced record breaking heat during early May.
Conversely, many locations across the Northern Tier from the Pacific Northwest to the western Great Lakes experienced improving drought conditions over the last month, associated with an active storm track and a series of strong low pressure systems that moved across the central CONUS.
Enhanced Gulf Moisture associated with these storm systems also resulted in improving conditions across the Lower Mississippi Valley and eastern parts of the Southern Plains. Across the eastern CONUS, there were mixed degradations and improvements depending on where the heaviest rain fell over the last month.
During the June-August (JJA) season, La Niña conditions are forecast to persist, although slightly weaken. During JJA, La Niña typically leads to warm temperatures across much of the western CONUS, warm and dry conditions across the central CONUS, dryness in the Southeast, and wetter than normal conditions in the Great Lakes and Northeast.
Drought is likely to persist across much of the Western CONUS, with some development also likely in areas experiencing abnormally dry (D0) conditions in Eastern and Northern Rockies, associated with La Niña and warm and dry signals in the monthly and seasonal temperature and precipitation outlooks.
Conversely, some improvement is forecast for the southern parts of the Four Corners, associated with the climatological start of the North American Monsoon in early July, which typically lasts beyond the end of August. In the Great Plains, although some temporary drought relief may occur through the end of June in the Northern Plains, the drought persistence is broadly favored.
Some drought development is forecast across parts of the Corn Belt, where precipitation signals are lacking and soil moisture is dry to start the season. Favored above-normal temperatures and a drier time of year also favor some drought development across the eastern parts of the Southern Plains.
Additionally, the start of the Atlantic Hurricane Season coincides with the start of the JJA season. The Atlantic Hurricane Season approaches its peak intensity (climatologically) toward the end of August, which does add some uncertainty to the forecast across the south-central CONUS.
Across the eastern CONUS, drought improvement and removal are broadly favored with near to above-normal precipitation favored at the monthly and seasonal leads and many areas entering into a climatologically wetter time of year.
Despite some dryness in western Alaska, no drought development is likely, as the state is entering into its wettest time of year. Drought persistence and development are likely in Hawaii, as the drought developed earlier this year during its rainy season and is now entering into a climatologically drier time of year.
Although some temporary drought degradation is possible in Puerto Rico, longer-term precipitation signals and the climatological ramp up of the Atlantic Hurricane Season favor drought removal by the end of August.
Forecast confidence is high for the Western Region.
- JJA is typically a drier time of year for the West Coast and much of the Intermountain West. The drier period, coupled with predominantly above-normal temperatures and near to below-normal precipitation favored during the JJA season, makes persistence the likeliest scenario by the end of August for most areas.
- Across parts of the Eastern Rockies and the Front Rangedrought development is also likely by the end of August, as favored above-normal temperatures and below-normal precipitation are expected to exacerbate conditions in areas already experiencing abnormally dry (D0) conditions.
- Across the interior Pacific Northwest, an active storm pattern in recent weeks, and the resulting increase to above-normal snow water equivalent (SWE) across most basins, offset the warm and dry odds for temperature and precipitation during JAA, respectively.
- However, La Niña conditions typically result in warmer than normal conditions across much of the West. Given JJA is also a drier time of year and that La Niña is favored to continue through JJA, drought development is likely by the end of August in abnormally dry areas of the inner Pacific Northwest and Northern Rockies.
- In the Four Corners region, the North American Monsoon (NAM) climatologically starts by early July and lasts through (and beyond) the JJA season. Given the antecedent warm and dry conditions expected leading up to the climatological start of the NAM, there could be an increased potential for an enhanced monsoon circulation, if climatology holds true.
- There is also a tilt in the odds toward above-normal precipitation during JJA, predominantly during the latter half of the season. As such, drought improvement and removal is anticipated by the end of August across parts of Arizona and New Mexico.
Forecast confidence is high in the Central High Plains and low to moderate elsewhere in the High Plains Region
- The percentage of annual precipitation begins to diminish across the northern High Plains during JJA. Conversely, many areas across the Central Plains will remain in what is typically a wetter time of year.
- Despite the wetter climatology across much of the Great Plains, however, warmer and drier conditions are favored through the end of August. As such, widespread persistence is favored across the High Plains Region, with development near and along the Front Range, where probabilities for below-normal precipitation are increased (greater than 40 percent).
- Given weaker precipitation signals, climatology, and antecedent wetness across much of the Dakotas, no eastward expansion of drought is expected for the northern Great Plains. However, sub-normal soil moisture anomalies, favored above-normal temperatures during JJA, and weak precipitation signals favor some expansion across the east-central Plains and the central Corn Belt.
Forecast confidence is high for the Southern High Plains, low to moderate for eastern Texas and the central Gulf Coast, and high elsewhere for the Southern Region.
- Above-normal temperatures and below-normal precipitation are favored for much of the Southern Great Plains during JJA.
- Farther to the east for parts of the Lower Mississippi Valley and central Gulf Coast, short-range forecasts and long-range North American Multi-Model Ensemble (NMME) probabilities favor odds for near and above-normal precipitation, which is expected to lead to drought improvement across southern Louisiana.
- Farther west, warm and dry long-range conditions are likely to win out across the Southern Plains, where drought persistence and development are favored, which is also the case for southern Texas. Additionally, eastern Texas and parts of the Middle Mississippi and Tennessee Valleys are also entering into a drier time of year (although weakly so).
- However, extended and long-range forecasts are not favorable for any drought development to extend farther eastward than eastern Texas.
- It should be noted that the Atlantic Hurricane Season is expected to ramp up throughout the JJA season, from a climatological perspective. However, given the uncertainty associated with tropical activity during the season, antecedent conditions and long-range outlooks were weighed more heavily for the Southern Region.
Forecast confidence is moderate for the central Corn Belt and high elsewhere in the Midwest Region.
- Drought persistence is likely in the western Corn Belt, where above-normal temperatures and below-normal precipitation is favored.
- Drought is also forecast to expand eastward into parts of the central Corn Belt in areas with antecedent dry soil moisture conditions.
- Elsewhere in the Midwest Region, soil moisture conditions are in good shape at the start of the period, despite the warmer temperatures that are favored at longer lead times. As such, no drought development is likely elsewhere across the Midwest Region by the end of August.
Forecast confidence is high for the Southeast Region.
- In addition to wetter than normal ERFs, several locations, particularly along coastal areas of the Southeast where drought conditions are most prevalent (D1-D2), are entering into a climatologically wetter time of year.
- Also, given the climatological ramp up of the Atlantic Hurricane Season during JJA and the start of the sea breeze circulation across Florida during June, drought removal (D1-D2 in Florida and D1 in the Carolinas and Virginia) and improvement (D2 in the Carolinas) are likely by the end of August.
Forecast confidence is high for the Northeast Region.
- Drought conditions in the Northeast Region have slowly improved in recent months.
- Despite the above-normal temperatures favored throughout JJA and equal chances for above, below, and near-normal precipitation, with a tilt in the odds toward above-normal precipitation for coastal areas, indicate slow changes are likely to continue.
- Given the wetter ERFs, drought removal is favored in remaining D1 areas across New England. No drought development likely elsewhere across the Northeast Region.
Forecast confidence is high for Alaska.
- Some abnormal dryness has popped up in southwestern Mainland Alaska, near the Yukon Delta. However, much of the state is coming into their wettest time of year. So the abnormal dryness is not favored to stick around through the end of August.
- Elsewhere, SWE is above-normal across the state, indicating that no drought development is likely.
Forecast confidence is moderate for Hawaii.
- In Hawaii, drought conditions developed and intensified during the winter months (the rainy season). Unfortunately, JJA is typically a drier time of year. Additionally, the NMME is favoring near to below-normal temperatures and below-normal precipitation during JJA.
- Despite a recent wet trend and some drought improvement in recent weeks, initial antecedent dryness coming into a drier time of year does not bode well. Drought persistence is favored, with development likely in abnormally dry and some drought-free areas.
Forecast confidence is low to moderate for Puerto Rico.
- The last 30 to 90 days were drier than normal across much of PR, with widespread 90-day precipitation deficits of more than 4 inches, per Advanced Hydrologic Prediction Service estimates, and pockets of more than 6 inch deficits.
- Despite also favoring above-normal temperatures, NMME forecasts favor near-normal precipitation through the end of August.
- With the threat of the Atlantic Hurricane Season looming as the JJA season progresses and La Niña conditions likely to continue through the end of Summer, drought removal is favored in areas experiencing moderate drought (D1) conditions, with the entire island favored to be drought free by the end of August.
- However, there could be some short-term degradation before conditions improve, given the recent short-term (30 to 90-day) dryness.