A La Niña Advisory remains in effect, with a 60% chance that La Niña conditions will transition to ENSO-neutral during the Northern Hemisphere Spring. As such, La Niña will likely influence conditions across the U.S. during April.
Drought conditions have persisted across the western CONUS during March, with only minor improvements observed following the passages of transient storm systems. Parts of the Pacific Northwest have received above-normal seasonal precipitation since the fall 2020, which has resulted in above-normal snowpack and reservoir levels leading up to April.
However, March precipitation remained below-normal for most locations. With below-normal temperatures and equal chances of above or below-normal precipitation in the Pacific Northwest, and a lack of temperature and precipitation signals along the central and southern West Coast, drought persistence is likely throughout the West.
Only D1 areas along the windward slopes of the Cascades in Oregon might see some drought removal. The Central Plains experienced a strong storm system that dropped heavy snow in parts of southeastern Wyoming and eastern Colorado, and heavy rain eastward to the Midwest, in mid-March.
Meanwhile, the Dakotas saw continued drought intensification from below-normal seasonal snowpack and above-normal temperatures during March. Wet signals across the Northern Plains during April are not strong enough to indicate major improvements are likely for locations entrenched in severe (D2) and extreme (D3) drought.
However, removal may occur for some locations in the eastern Dakotas, as antecedent dryness is not as pronounced as areas farther west.
Drought persistence, with some additional development in abnormally dry (D0) areas, is also likely across the Central and Southern Plains. Despite varying wet signals, temperatures are likely to remain above-normal throughout April. The Plains are also prone to high-wind events during the period, which could exacerbate dry conditions further.
The upper Midwest, Tennessee Valley, middle Mississippi Valley, and the southern Louisiana coast received beneficial rainfall during March, warranting some improvements in drought conditions, and staving off further development in these regions during April, given the weakly below-normal to lack of a precipitation signal.
Locations in the central and eastern Great Lakes and Northeast have missed out on some of the heavier precipitation from passing storm systems, increasing coverage of abnormally dry (D0) areas and leading to some expansion of moderate (D1) drought. Above-normal temperatures are favored across the region, and with the lack of a precipitation signal (leaning below-normal toward the Northeast in some of the forecast tools), conditions are likely to deteriorate.
Conditions in the Northeast may also be exacerbated by an early start to vegetation growth, due to increased water uptake from the soils and increased evapotranspiration rates.
In Florida, antecedent dryness, increased odds of above-normal temperatures and below-normal precipitation, and April typically being a dry month climatologically, indicate a greater likelihood for deterioration across the Florida Peninsula.
No drought development is likely in Alaska. Enhanced odds of below-normal temperatures early in April eliminate the likelihood for exacerbation of abnormally dry (D0) conditions in the north. Additionally, above-normal precipitation favored throughout the month over much of the western Mainland, and equal chances for above or below normal precipitation elsewhere, further supporting the drought-free depiction for April.
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Heavy rain and flooding in recent weeks in Hawaii has led to removal of drought across the islands. Above-normal precipitation is favored for much of the state during April, indicating Hawaii is likely to remain drought-free. Moderate (D1) drought in northwestern Puerto Rico diminished slightly with above-normal precipitation in recent weeks and improved drought indicators.
Despite above-normal temperatures favored in the long-term guidance, above-normal precipitation is also favored, suggesting drought removal is likely, making Puerto Rico drought-free also by the end of April.
Forecast confidence is moderate to high for the Western Region.
- In the West, snow water equivalent (SWE) and reservoir levels are above-normal for the season leading up to April in the Pacific Northwest and northern Great Basin, falling quickly to below-normal southward in the Western Region.
- However, March saw below-normal precipitation across the West, leading to some expansion of moderate drought (D1) in some locations in eastern Washington and northern Montana.
- Odds for below-normal temperatures indicate existing drought conditions will not likely be exacerbated further during April. Additionally, the lack of a precipitation signal, coupled with surplus snowpack and above-normal reservoir levels, suggests no major improvements either.
- As such, persistence is favored for much of the Pacific Northwest, with improvement favored along the western Cascades.
- Further south, drought persistence is also likely, with no additional development, as temperature and precipitation signals are lacking along the West Coast and western portions of the Great Basin.
- Further east, in the eastern Great Basin, below-normal precipitation is favored in areas already experiencing moderate to exceptional drought, indicating persistence is likely.
Forecast confidence is low for the Northern Plains and moderate elsewhere for the High Plains Region.
- The Northern Plains in the High Plains Region is a victim of below-normal seasonal snowfall and above-normal temperatures (6-10°F above-normal). This has resulted in drought expansion and intensification across the Dakotas and into the upper Midwest in the months leading up to April.
- The Dakotas are favored to experience above-normal precipitation (33% – 40% chance), with the greatest chances during the first half of the month.
- Additionally, the Great Plains begins its transition into a wetter time of year climatologically toward the end of April, in addition to a typical slight enhancement of wet precipitation signals across the region during La Niña years.
- Despite the potential for above-normal precipitation, lower probabilities indicate lower confidence, and any precipitation received will need to be much above-normal to overcome antecedent, long-term severe (D2) and extreme (D3) drought conditions across the Dakotas.
- However, some removal is favored in areas experiencing moderate (D1) drought in the eastern Dakotas, as drought indicators show weaker signals leading into the April period, suggesting any precipitation received will be more impactful. However, it should be noted that any potential improvements in the Dakotas will be slow to develop.
- Further south, the Central Plains experienced a major winter storm system in mid-March, which dropped 2-3 feet of snow in portions of eastern Colorado and southeastern Wyoming and anywhere from 5-10 inches of rainfall from the Front Range eastward to the Midwest, which brought major drought improvement.
- However, with above-normal temperatures and below-normal precipitation favored for the western High Plains, drought conditions are likely to persist during April.
- Furthermore, drought development is likely in abnormally dry (D0) areas, including those affected by the strong March storm system, as these areas are prone to high-wind events and conditions are favored to dry out again during April.
Forecast confidence is moderate for the Midwest Region.
- In the Midwest, portions of the Corn Belt have seen beneficial rainfall in the weeks leading up to April, resulting in drought removal across central Illinois.
- Elsewhere, however, below-normal precipitation has led to drought expansion across southern Michigan and northern portions of Ohio. Drought development also occurred across northern Minnesota.
- Above-normal precipitation is weakly favored for much of the Midwest during the next 6 to 10 days, transitioning to below-normal during Week-2 (8 to 14 days).
- Due to increased odds of above-normal precipitation early in the period, and above-normal precipitation favored in the April precipitation outlook in the upper Midwest, drought removal (D1) is likely across Minnesota.
- Additionally, standardized precipitation indices (SPIs) have shown gradual improvements in recent months, suggesting above-normal precipitation is likely to have more immediate impacts (although to a lesser extent in farther west in Minnesota and the eastern Dakotas, where dry signals in drought indicators are more pronounced).
- However, in portions of western and southern Michigan and northern Ohio, drought persistence, with additional expansion into abnormally dry (D0) areas, is likely, with above-normal temperatures strongly favored and precipitation signals transitioning to below-normal eastward toward the eastern Great Lakes and Northeast.
Forecast confidence is moderate for the Southern Region.
- The Texas Panhandle, northern and northwestern Oklahoma, the Tennessee Valley, and portions of the middle and lower Mississippi Valley experienced above-normal precipitation and drought removal during March.
- This beneficial improvement will be much needed during April, as equal chances of above or below to below-normal precipitation is favored throughout the Southern Region.
- Predicted weak mid-level height patterns during the middle part of the month increases uncertainty a bit in which location could see continued improvement versus degradation.
- As such, drought persistence is favored across the Southern Region, with development likely in abnormally dry (D0) areas across portions of west-central and southeastern Texas and southwestern Oklahoma, as well as the Texas and Oklahoma Panhandles.
- However, further eastward toward the lower Mississippi Valley, greater uncertainty among the model precipitation signals makes persistence (northeastern Louisiana) with no further development likely.
Forecast confidence is moderate to high for the Southeast Region.
- Heavy precipitation across the Southeast during the latter half of March led to some drought removal across areas of the Deep South.
- However, dryness has persisted in Florida, resulting in drought development in southern portions of the Peninsula in the past couple of weeks.
- In addition to April being a climatologically dry month for Florida, enhanced odds of above-normal temperatures and below-normal precipitation are favored, increasing the likelihood of additional drought expansion across the Florida Peninsula during April.
Forecast confidence is moderate to high for the Northeast Region.
- In the Northeast, long-term drought has slowly diminished in recent months. However, D0 to D2 standardized precipitation indices (SPIs), locally D3, are still prominent, extending from western Pennsylvania to northern New England.
- Unfortunately, relief is not likely to come during April, as below-normal precipitation is favored through the first half of the month. Additionally, recent medium-range model solutions point toward equal chances for above and below to below-normal precipitation at longer leads.
- Coupled with increased odds of above-normal temperatures and plant growth being ahead of schedule (increasing evapotranspiration and water uptake in the root zones), this is likely to exacerbate existing dryness, suggesting drought development is likely in the driest areas from the Shenandoah Valley into western Pennsylvania, northern and western New York, New England, and western Maine.
Forecast confidence is high for Alaska, Hawaii, and Puerto Rico.
- D0 currently covers much of northern Alaska, extending across the North Slope and Brooks Range southeastward to the Yukon Flats. Basin SWE estimates are currently below-normal (near 60% of normal for the period of record) across central Alaska.
- However, above-normal precipitation is favored throughout the period across the western Mainland, with equal chances for above or below elsewhere, which will help to stave off drought development throughout April.
- In Hawaii, many areas received heavy rainfall in recent weeks, with several locations experiencing flooding. As the wet season winds down during April, the state is expected to continue to see above-normal precipitation, making drought removal likely for the entire state.
- Moderate drought (D1) is currently depicted in northwestern Puerto Rico. Despite above-normal temperatures favored during April, above-normal precipitation is also favored.
- Coupled with continued improvements in SPIs in recent weeks, this area is primed for continued improvement, making complete drought removal likely for the island.