Nationwide
Following the El Niño winter and an active early spring pattern, drought coverage is at its lowest since spring 2020.
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A strengthening low-pressure system and trailing cold front progressed east from the Mississippi Valley to the East Coast at the beginning of April. This storm brought heavy snow (6 to 18 inches, locally more than 2 feet) to the Upper Peninsula of Michigan, Wisconsin, and northern New England. The recent precipitation (rain and snow) during the past few weeks continued to ease drought conditions across the Upper Midwest.
From April 5 to 7, a strong storm system tracked east from the Rockies to the Great Plains. Heavy snowfall (6 to 12 inches, locally more) occurred across parts of Idaho, Montana, and Wyoming. Total precipitation of 1-2 inches, liquid equivalent, improved drought from the north-central Rockies to western South Dakota. Drought continued to develop or intensify across parts of the southern Great Plains, lower Ohio Valley and Hawaii.
Please note that heavy rainfall across the South occurring after April 9th at 8 a.m. EDT will be considered in next week’s U.S. Drought Monitor.
The West
As a low-pressure system shifted inland, widespread precipitation (rain and high-elevation snow) overspread the West from April 3 to 6.
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Heavy precipitation (more than 1.5 inches, liquid equivalent) along with snow water equivalent (SWE) amounts near average supported a 1-category improvement to western Idaho and northeastern Oregon. Parts of western Montana also had a 1-category improvement due to a wet week and considerations such as SWE and Standardized Precipitation Index (SPIs) at various time scales. The current depiction of moderate to severe drought across Idaho and western Montana lines up well with the 6 to 9-month SPI.
On April 5 and 6, a major storm developed across the northern Rockies and high Plains, with precipitation exceeding 1.5 inches (liquid equivalent) across southern Montana. Based on this heavy precipitation and lack of support from SPIs at various time scales, a one-category improvement was made to this region. Neutral to positive SPIs at multiple time scales and SWE near to slightly above normal supported the removal of D0 (abnormal dryness) from western Nevada and adjacent areas of California.
Farther to the north, low snowpack resulted in a second week of D0 and D1 expansion across north-central and northeastern Washington. Although it was a mostly dry week for the Southwest, reassessing SPIs at various time scales led to targeted improvements for parts of New Mexico.
The High Plains
Widespread rain and snow (1 to 2 inches of precipitation, liquid equivalent) on April 7 led to a 1-category improvement across parts of northeastern Wyoming and western South Dakota. Despite the recent heavy precipitation, 6-month SPI along with 28-day average streamflow support a continuation of moderate drought (D1) across the High Plains.
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Following another week of precipitation, along with considerations of soil moisture and SPI values of neutral to positive, abnormal dryness (D0) coverage was reduced throughout the Dakotas. A strengthening low-pressure system on April 6 and 7 brought high winds to the Great Plains, drying out topsoil, especially across Kansas and southeastern Colorado. A reassessment of SPIs at various time scales, and given that snow water equivalent is slightly above average, D1 coverage was reduced for southern Colorado.
The South
Major drought relief, associated with El Nino, occurred this past winter across the lower Mississippi Valley.
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Precipitation from April 2-8 led to a small decrease in abnormal dryness (D0) and moderate drought (D1) in parts of this region. Heavy precipitation that occurred after 7 am CT Tuesday, April 9th, will be factored into next week’s depiction. A strengthening low-pressure system on April 6 and 7 brought high winds and elevated wildfire danger to the southern Great Plains, which dried out topsoil, especially across northwestern Oklahoma. 30 to 90-day SPEI and the lack of vegetation green-up supported an expansion of D0 and D1 across parts of Oklahoma. Northern Arkansas and northwestern Tennessee also increased in D0 and D1 coverage as short-term precipitation deficits grew to 60 days. — UNL Drought Monitor
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