There have not been significant changes to the incipient drought situation since the release of the April – June seasonal drought outlook.
Recent forecasts for the western U.S. have changed considerably over the past few days, however, with short term forecasts depicting a heavy rainfall event along coastal northern California, Oregon, and Washington, with heavy late season snowfall across the Cascades and northern Sierras.
A regime of below-normal temperatures and potential for additional storminess is forecast to persist through the first half of April. Therefore, some amelioration of drought is possible where the heaviest coastal rains and mountain snows occur, particularly across the far northern California and Oregon coasts and the Cascades of northern Oregon.
Small short term improvements are also favored for northeastern Arizona due to improving conditions.
No additional drought development is anticipated to occur across the West during April, although continued low snowpack conditions across the Sierras and other parts of the Intermountain West may potentially be a cause for concern beyond the forecast period.
Heavy early month rainfall is also forecast across much of Texas and the Gulf Coast, which should ameliorate ongoing short term drought conditions. In contrast, hot, dry weather is favored to persist across the Florida Peninsula, favoring short term drought development.
The pattern across the central U.S. is likely to be highly variable during April, with an active southern stream early in the period favoring cyclogenesis and enhanced precipitation generally northeast of the ongoing drought areas of the south-central High Plains.
Due to recent dryness and little to no precipitation anticipated during the first half of April, drought expansion is possible across northeastern New Mexico, western Oklahoma, and far southwestern Kansas.
Elsewhere, a Nor’easter brought improved soil moisture conditions to southern New England, making April drought development less likely, while persistent midlatitude cyclonic circulation west of Hawaii has caused copious rainfall accumulations, favoring continued drought reduction.
Forecast confidence is moderate for the Western Region.
- Drought conditions gradually worsened across the Pacific coastal states and Great Basin during March following a lackluster core of the wet season, although a late season surge of moisture brought some limited improvements to parts of the Sierra Nevadas and southern Great Basin.
- Following this late season storminess at the end of March, long range forecasts issued prior to the April – June 2020 seasonal drought outlook (SDO) depicted a return to drier conditions to end the wet season. Therefore, gradual drought expansion was favored across the West and Great Basin through the remainder of the Spring and early Summer.
- More recent forecasts have shifted the pattern considerably, however, and now depict a continuation of the late season moisture surge that began in late March, with troughing bringing below-normal temperatures.
- In particular, the 7-day quantitative precipitation forecast (QPF) from the Weather Prediction Center (WPC) shows a heavy precipitation event across coastal northern California northward to Washington, with heavy snowfall across the Cascades and to a lesser extent the Sierras.
- This late season moisture boost may bring some drought improvement to the coastal areas of extreme northern California and Oregon as well as the Oregon Cascades.
- Further south, continued low snowpack conditions and lower accumulations limit the potential for late season improvements across the Sierras, but some improvement to ongoing drought conditions is possible for northeastern Arizona.
- Due to the unsettled weather and below-normal temperatures expected during the first half of April, no additional drought development is anticipated across the Pacific coastal states or Great Basin.
- Further east, dry weather has predominated across northeastern New Mexico, and the first half of April is anticipated to remain almost completely dry. Therefore, slow drought expansion is favored across northeastern New Mexico.
Forecast confidence is low for the High Plains Region.
- Drought conditions persist across parts of Colorado, western Oklahoma, and western Kansas, as heavier precipitation missed this region both to the north and the south.
- April weather conditions can be quite variable across the Plains, as moisture surges from the Gulf of Mexico alternate with late season cold pushes from Canada, often resulting in severe weather outbreaks.
- The updated April monthly outlook from CPC favors above-median precipitation across the northern Plains, while near to below-median precipitation is favored during the first half of the month across southeastern Colorado and southwestern Kansas.
- Therefore, slight drought expansion may occur across southwestern Kansas, but no additional drought development is anticipated across the High Plains Region.
Forecast confidence is high for the Southern Region.
- Developing storm systems associated with an active southern stream brought heavy precipitation and drought relief to parts of central Texas and southwestern Oklahoma, while persistent dryness aggravated the substantial short term drought conditions across South Texas.
- Precipitation also largely missed the immediate Gulf Coast, resulting in drought expansion across parts of Louisiana.
- During early April, the active storm pattern is favored to continue, with a southward shift bringing widespread heavy rainfall to southeastern Texas and the central Gulf Coast. Due to the short term nature of the drought conditions, this forecasted wetness should be sufficient to alleviate drought across parts of Texas and the central Gulf Coast.
- The CPC 8-14 day and updated April outlooks favor a continuation of the wet pattern across eastern Texas and the Gulf Coast, bringing higher confidence for this improvement.
- Elsewhere, ongoing Spring thunderstorm activity is anticipated to remove drought across southern Oklahoma, while drier conditions further west may promote drought expansion across the far northwestern Texas Panhandle and western Oklahoma Panhandle, similar to the situation in northeastern New Mexico.
Forecast confidence is high for the Midwest Region.
- No drought is currently in place across the Midwest Region, and no drought development is anticipated.
- River flooding is likely to be a greater concern for the Midwest than drought during the Spring.
Forecast confidence is high for the Southeast Region.
- The mean storm track during March strongly favored excessive wetness across the Tennessee and Ohio Valley regions, with below-normal precipitation observed along the Gulf Coast and much of Virginia.
- In particular, much below-normal rainfall and hot conditions prevailed across Florida, resulting in a rapid increase of Keetch-Byram Drought Index (KBDI) values across southern Florida, with some moderate drought (D1) developing over interior Southwest Florida.
- During early April, the 7-day QPF from WPC shows the potential for a wide swath of heavy rainfall along the Gulf Coast, with the 8-14 day ERF and updated April monthly outlooks from CPC continuing the wet pattern. However, the tools maintain a sharp precipitation gradient along the Florida Panhandle, with much less rainfall anticipated across the Peninsula.
- Abnormally hot conditions are favored to continue across Florida and parts of the Southeast during April as well. Therefore, drought development is forecast for most of the Florida Peninsula.
- Parts of Virgina may also be susceptible to drought development, but rainfall during the first half of April is anticipated to be adequate to prevent substantial degradation of soil moisture conditions, and the updated April outlook maintains equal chances for below-, near-, and above-median precipitation.
Forecast confidence is moderate for the Northeast Region.
- Late season snowpack conditions remain well below normal across New England, and 30-day percent of normal precipitation ranges generally between 50 and 100 percent across Maryland and much of New England, while moisture conditions are better across western Pennsylvania and the Canadian border region.
- A late month Nor’easter brought a boost of moisture to southern New England, where precipitation deficits were previously the highest.
- The updated monthly outlook from CPC shows no tilt towards abnormal dryness. Therefore, while the region remains susceptible to drought development during the Spring and early Summer, drought development is not anticipated to occur during April.
Forecast confidence is high for Hawaii.
- A persistent midlatitude cyclonic circulation west of Hawaii has promoted surges of tropical moisture, resulting in widespread flash flooding and severe weather, particularly across the western islands.
- An ongoing Maritime Continent MJO event teleconnects to a continuation of this pattern early in the month.
- While continued MJO activity may flip the pattern later in the period, the recent extreme precipitation and anticipated continuation of the wet pattern in early April favor continued drought reduction for Hawaii, and no additional development.