A couple of low pressure systems resulted in widespread precipitation (0.5 to 3 inches, locally more) across the central and southern Plains, Ohio and Tennessee Valleys, Southeast, and Mid-Atlantic from March 16 to 22.
However, mostly dry weather persisted across southern Texas, the Florida Peninsula, northern New England, the Great Lakes, and northern Plains. Periods of rain and high-elevation snow occurred across the Pacific Northwest, northern California, and the central Rockies, but the Southwest remained mostly dry.
As of March 23, 7-day maximum temperatures averaged above normal across the northern Plains and Upper Mississippi Valley.
On March 17 and 18, a severe weather outbreak occurred with numerous tornado reports across Alabama, Georgia, Florida, North Carolina, and southeast Virginia. In addition to the severe weather, widespread rainfall (0.5 to 2 inches, locally more) soaked much of the Southeast which prompted a 1-category improvement to ongoing D0 (abnormal dryness) and D1 (moderate drought).
28-day streamflows and 60 day SPI values continue to support lingering areas of D0-D1 across Alabama. Parts of northern and central Georgia received less rainfall this past week which prompted an increase in abnormal dryness (D0) based largely on 60-day SPI.
The Florida Peninsula remained mostly dry this past week and the D0 (abnormal dryness) was expanded. D1 (short-term moderate drought) was added to mainland areas of Monroe County in south Florida where less than 2 inches of rainfall has occurred during the past 90 days and fire danger is very high.
The severe weather outbreak that affected the Southeast Region began across the Lower Mississippi Valley on March 17 and local rainfall amounts exceeded 2 inches across parts of Arkansas, Louisiana, and Mississippi where 1-category improvements were made. More widespread rainfall amounts of more than 1.5 inches increased soil moisture throughout nearly all of Tennessee.
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Based on this past week’s rainfall of 1 to 3 inches and improving soil moisture conditions, improvements were made to much of Oklahoma and parts of northern to central Texas. Small 2-category improvements were justified for the northeast Texas Panhandle and northwest Oklahoma where the heaviest rainfall occurred.
Periods of above normal temperatures, enhanced surface winds, and below normal precipitation this month supported a continued worsening of drought conditions throughout southern Texas. Soil moisture declines rapidly from central to west Texas where indicators support D3 (extreme) to D4 (exceptional) drought categories.
Widespread precipitation (0.5 to 2 inches) fell from Missouri east to Kentucky, Illinois, Indiana, and Ohio on March 17 and 18. This recent precipitation maintained saturated soils, high streamflows, and minor to moderate river flooding across the Middle Mississippi Valley and Lower Ohio Valley.
In areas that were drier preceding this precipitation, extending from northeast Missouri east to Ohio, a large decrease in D0 (abnormal dryness) and D1 (moderate drought) coverage was warranted. However, this recent rainfall had to be balanced with longer term SPIs.
There was a sharp northward cutoff to this precipitation and D0-D1 coverage was increased across lower Michigan, extreme northern Indiana, and southern Wisconsin based on soil moisture and SPI values at various time scales.
Frequent precipitation during the past two weeks continues to result in additional improvements to parts of the central Plains and central Rockies. 7-day total amounts (March 16-22) ranged from 1 to 3 inches, locally more, across a broad region including south-central Nebraska and much of Kansas.
As of March 22, Grand Island Nebraska has received 6.95” so far this month which makes it the wettest March on record. The drought amelioration extends west to the central Rockies where numerous improvements were made including a two-category change from D3 to D1 in southwest El Paso County and southeast Teller County as SPIs are now D1 at all timescales.
The removal of D3 in southeast Colorado and southwest Kansas was based on: SPIs are either neutral or positive dating back to 6 months and improving soil moisture conditions. In contrast to the major improvements across the central Rockies and central Plains during the past two weeks, persistent dryness continues to support additional expansion of D2 (severe) and D3 (extreme) drought across parts of North Dakota.
A slight expansion of severe drought (D2) was made to northeast Montana, based on 90-day SPI and soil moisture below the 10th percentile. These low soil moisture conditions are related to the lack of snowfall this winter.
In contrast to the northern high Plains, snow water content is running close to average for late March and led to the elimination of abnormal dryness (D0) across south-central Montana. Since parts of western Arizona and southeast California have received little to no precipitation during the past two month, D3 (extreme) and D4 (exceptional) drought were slightly increased.
This expansion of D3-D4 was supported by 9-month SPI values which covers the failed 2020 monsoon and this past winter. An expansion of D2 (severe) and extreme (D3) drought across parts of southern California was based on large water year to date precipitation deficits and 6-month SPI values.
No other changes were made at this time to the remainder of California as 6 to 12 month SPIs generally support the current depiction and snow water content is running near two-thirds of average for the Sierra Nevada Mountains. During subsequent weeks, the drought depiction will be reassessed across California.
Although much of the precipitation this past week fell along the coast or over the Cascades, a reassessment of longer term SPIs dating back 6 to 12 months supported removal of the D2 (severe) drought in southwest Oregon.
Due in part to recent high-elevation snow and rainfall during the past two weeks, a slight decrease in D3 (extreme) and D4 (exceptional) drought was made to northern and northeast New Mexico. However, widespread D4 persists across southeast New Mexico where dust storms have been quite frequent this month and soil moisture remains in the lowest one percentile.
Following below normal precipitation during the first half of March, widespread precipitation (0.5 to 1.5 inches) overspread the northern Mid-Atlantic and southern New England. However, much of Maine, northern New Hampshire and Vermont, Upstate New York, and parts of Massachusetts remained mostly dry. Therefore, a slight increase in D0 (abnormal dryness) and D1 (moderate drought) was made.
Although 28-day streamflows generally are running average, soil moisture and SPI values at various time scales support the ongoing D0 and D1. Also, areas east of Lake Erie (northeast Pennsylvania and western New York) had an expansion of D0 this week.
Alaska, Hawaii, and Puerto Rico
Abnormal dryness continues for northern and eastern Mainland Alaska with no changes this week. As of mid-March the water year precipitation remains below 70 percent for northeast parts of Alaska.
Numerous preliminary reports of 6-day totals, ending on March 13, exceeded 10 inches across parts of these islands and maximum amounts of more than 20 inches were reported. Based on this heavy rainfall during mid-March, a broad 1-category improvement was made to Hawaii which results in limiting long-term drought (D1) to only Maui.
After above normal precipitation resulted in a decrease of abnormal dryness (D0) and short-term moderate drought (D1) during the previous week, drier weather returned and no changes were made to Puerto Rico.
During the next 5 days (March 25 to 29), a pair of low pressure systems are forecast to bring widespread precipitation (0.5 to 2 inches, locally more) to the Lower and Middle Mississippi Valley, Ohio and Tennessee Valleys, and Northeast.
Farther to the south across the Florida Peninsula and southern Texas, dry weather is likely to persist. Little to no precipitation is also forecast for the northern Great Plains. Additional snow is expected throughout the Rockies, Intermountain West, and Cascades.
The CPC 6-10 day extended range outlook (valid from March 30 to April 3) favors near normal temperatures for much of the lower 48 in a variable pattern.
Probabilities of above normal temperatures are elevated for the northern Plains, Florida, and California. Below normal temperatures are most likely across Alaska.
Above normal precipitation is favored for the Northeast, Mid-Atlantic, western Gulf Coast, Rio Grande Valley, and Alaska. Increased chances of below normal precipitation are forecast across the Upper Mississippi Valley, much of the Plains, and throughout the West.