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, April-May-June (AMJ). As such, La Niña will likely influence conditions across the U.S.
Although La Niña signals typically dissipate during AMJ across the CONUS, it could influence the tropics late in the period. However, its potential effects on the tropics are not considered in this month’s Seasonal Drought Outlook (SDO), given increased uncertainty three months from now related to multiple factors that can influence tropical activity.
During the past month, no major overall expansion of drought coverage was experienced nation-wide. However, varying regional changes are evident. The Pacific Northwest saw reduction in drought coverage due to above-normal seasonal precipitation resulting in above-normal snowpack and near to above normal reservoir levels.
Drought removal is likely to continue in south-central Washington and north-central Oregon for these reasons. Although the Central and Southern Rockies saw some improvements, many of those areas remain in extreme (D3) to exceptional (D4) drought, with drought persistence likely.
Development is likely in abnormally dry (D0) areas also, as temperatures and precipitation are expected to remain above and below-average, respectively. Dryness across the Northern Plains continued, exacerbated by below-normal winter snowfall totals and above-normal winter temperatures.
North Dakota experienced its driest September to February period on record. Extreme cold across the Great Plains during February further exacerbated drought impacts, adversely affecting winter wheat and livestock.
However, in the week leading up to the SDO release, a strong winter storm dumped heavy snow and rain across the Central Plains, delaying any further degradation in the short-term, but long-term drought indicators remain very dry and long-range models favor below-normal precipitation and increased chances of above-normal temperatures, hence drought persistence in the Northern Plains, with development likely in the Central Plains.
A wetter-than-average AMJ is forecast for much of the Midwest and Northeast, indicating drought removal (D1) is likely for those regions. In the Southern Region, drought persistence and development are favored across Texas and Oklahoma, associated with favored above-normal temperatures and below-normal precipitation during AMJ.
Farther east in Louisiana and Alabama, short-term (Week-2) wetness favors drought removal in northern Louisiana and central Alabama (Southeast Region). Conversely, increased chances for below-normal precipitation at the monthly and seasonal time scales indicate drought persistence is likely in southern Louisiana, despite short-term wet signals.
Abnormal dryness in the Florida Panhandle is likely to develop into drought during the first two-thirds of the period (April and May), with increased odds of above-normal temperatures (April-June) and below-normal precipitation (April). However, uncertainty increases in June, as Florida enters a climatologically wetter period and the potential for rapid removal of any drought that develops early in the period.
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Development is more likely across the Florida Peninsula due to recent drying and the likelihood of below normal precipitation during the remainder of March through April.
No development is likely in Alaska, with above-normal precipitation favored over much of the western Mainland, and equal chances for above or below normal precipitation elsewhere. Heavy rain and flooding in recent weeks in Hawaii fell mainly in areas not currently depicted in drought.
However, above-normal precipitation is favored for much of the state early in the period, indicating drought removal is likely. Moderate drought (D1) in northwestern Puerto Rico diminished slightly this past week with above-normal precipitation in recent weeks and improved drought indicators. However, with above-normal temperatures and only near-normal precipitation favored during AMJ, drought persistence is forecast.
Forecast confidence is high for the Western Region.
- Drought is expected to persist across much of the West, with removal favored for south-central Washington and north-central Oregon.
- Snow water equivalent (SWE) and reservoir levels are above-normal for the season leading up to the AMJ period for the Pacific Northwest and northern Great Basin, falling quickly to below-normal southward in the Western Region.
- As surplus snowpack melts during the AMJ season, moderate (D1) and severe (D2) drought in southern Washington and northern Oregon will likely result in drought removal.
- Conversely, widespread above-normal temperatures and below-normal precipitation are favored for much of the central and southern Western Region, indicating drought is likely to persist across much of the remainder of the region, with development likely in D0 areas along the California coast and southwestern Arizona.
Forecast confidence is moderate for the High Plains Region.
- The High Plains Region is a tale of weather and climate extremes.
- North Dakota saw its driest September-February period on record, with other states seeing below to much below-normal September to February periods for precipitation.
- This past week, however, the Central Plains experienced a major winter storm system, which dropped 2-3 feet of snow in portions of the Colorado Rockies and southeastern Wyoming. A swath of 5-10 inches of snow extended eastward from the central High Plains and into the Midwest.
- On the warm side of the storm, areas of northern Kansas and southern Nebraska saw widespread 2-3 inches of rainfall, with a pocket of 5-6 inches in southeastern Nebraska. Areas that saw the heaviest snowfall remain depicted in D0 (abnormally dry), but could continue to see short-term improvements as the snow melts and absorbs into the soils.
- Additionally, the High Plains Region is entering into a climatologically wetter time of year, particularly during the latter two-thirds of the AMJ period with an increasing potential for severe weather during the season.
- Despite the wetter time of year on average, medium and long-range models depict an enhanced potential for above-normal temperatures and below-normal precipitation for the season. The above-normal precipitation signal diminishes to equal chances for above or below farther north in the High Plains Region.
- However, antecedent short and long-term dryness will be difficult to overcome, even if near-normal precipitation is observed during the AMJ season, due to the likelihood of above-normal temperatures increasing the potential for soil moisture loss.
- Therefore, drought persistence is likely for the High Plains Region with drought development for portions of the Central Plains, and for D0 areas along the Front Range, where odds of above-normal temperatures and below-normal precipitation are greatest.
Forecast confidence is moderate for the Midwest Region.
- Short to long-term dryness continued across portions of the Corn Belt since the March-April-May SDO release, with eastward to northeastward expansion of D0 and D1 across northern Ohio and southeastern Michigan. Additional eastward D0 expansion occurred across the upper Midwest Region into Wisconsin and the Upper Peninsula and western Michigan.
- Despite the short-term dryness, precipitation chances are above normal across much of the Great Lakes, stretching to the Mid-Atlantic, with equal chances for above or below normal precipitation west of the Great Lakes.
- Above-normal temperatures are also favored across this region, so any periods of dryness could prove detrimental in areas with existing abnormal dryness (D0). As such, drought persistence is favored for western areas of the Midwest Region with removal likely in D1 areas in the Corn Belt and along the west coast of Lake Erie, where probabilities of above-normal precipitation are greatest.
Forecast confidence is high for Oklahoma and Texas and low to moderate for the Lower Mississippi Valley.
- With enhanced probabilities of above-normal temperatures and elevated odds of below-normal precipitation across the Southern Region, drought persistence with additional expansion is likely for large portions of Oklahoma and Texas. Below-normal precipitation signals diminish eastward in the Southern Region during AMJ.
- Farther east in the region, short-term wetness is favored through the Week-2 period, with drought removal likely in northern Louisiana in the short-term.
- Despite short-term wet signals in southern Louisiana, long-term guidance, monthly outlooks, and seasonal outlooks suggest increased odds for above-normal temperatures and below-normal precipitation, indicating persistence is more likely there.
Forecast confidence is low for Florida and moderate to high elsewhere for the Southeast Region.
- In the Southeast, recent heavy precipitation across Alabama, in addition to increased odds of above-normal precipitation across much of the Southeast during the next two weeks, favors drought removal in central Alabama in the near-term, with no re-development likely beyond that time.
- Eastern portions of the Southeast Region, including Florida, will begin the transition into a wetter time of year toward June. However, with increased odds of above-normal temperatures during AMJ, antecedent dryness, and the late transition to the wet season for these areas, drought development is favored in and around D0 areas in the central and southern Florida Peninsula.
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) are still prominent, extending from western Pennsylvania to northern New England.
- From April to June, the region typically receives an increasing percentage of its annual precipitation.
- Despite above-normal temperatures favored across the region, above-normal precipitation is also favored for much of the region and in D1 areas in New England and Upstate New York. Therefore, drought removal is likely.
Forecast confidence is moderate to high for Alaska and Hawaii, and moderate for 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 across central Alaska, just south of the abnormally dry areas in the north. 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.
- In Hawaii, many areas that experienced heavy rains and flooding are not currently depicted in drought. Although Hawaii typically transitions into a drier time of year, long-range models depict increased probabilities of above-normal precipitation for much of the state early in the period, with equal chances for above and below-normal precipitation to above-normal precipitation favored for the remainder of the season. As such, drought removal is forecast for Hawaii.
- Moderate drought is currently depicted in northwestern Puerto Rico. Above-normal temperatures and near-normal precipitation are favored during AMJ. However, with La Niña to ENSO-neutral conditions expected to persist, it could influence the tropics toward the end of the period as we enter the Atlantic Hurricane season, but drought persistence is likely during AMJ.