National Drought Summary -- March 30, 2021

The discussion in the Looking Ahead section is simply a description of what the official national guidance from the National Weather Service (NWS) National Centers for Environmental Prediction is depicting for current areas of dryness and drought. The NWS forecast products utilized include the HPC 5-day QPF and 5-day Mean Temperature progs, the 6-10 Day Outlooks of Temperature and Precipitation Probability, and the 8-14 Day Outlooks of Temperature and Precipitation Probability, valid as of late Wednesday afternoon of the USDM release week. The NWS forecast web page used for this section is: http://www.cpc.ncep.noaa.gov/products/forecasts/.

Multiple low pressure systems resulted in widespread precipitation (0.5 to 3 inches, or more) from the Mississippi Valley to the East Coast during late March. Heavy to excessive rainfall (more than 5 inches) soaked southeast Louisiana and triggered flooding across Tennessee this past week. Along with the flooding, a severe weather outbreak affected Alabama, Georgia, Tennessee, and Kentucky on March 25. Mostly dry weather persisted farther to the south, including the Florida Peninsula and south Texas. A cold front brought strong winds to the northern Plains on March 29 but little or no precipitation. Rain and high-elevation snow was limited to coastal Washington and the northern Cascades across the Pacific Northwest, while mostly dry weather prevailed throughout California. 7-day temperatures from March 23-29 averaged below (above) normal across the western (eastern) U.S.


Alaska, Hawaii, and Puerto Rico

Abnormal dryness (D0) continues for northern and eastern Mainland Alaska with no changes this week. The depicted D0 will be reassessed next week as current snowfall data becomes updated.

Based on rainfall during mid to late March, a 1-category improvement was made on Maui, Molokai, Lanai, and Kahoolawe. Therefore, Hawaii is currently drought free with only lingering abnormal dryness (D0). Reports from Hawaii indicate a greening of vegetation on Maui but abnormal dryness continues on the northwest side of the Big Island.

According to AHPS, 7-day precipitation amounts across Puerto Rico averaged at or above normal from March 23 to 29. Due to heavier amounts across inland areas, a slight decrease in D0 (abnormal dryness) and D1 (moderate drought) was made to parts of Puerto Rico.


High Plains

Another dry week along with strong winds on March 29 resulted in a slight expansion of extreme drought (D3) across North Dakota and northern South Dakota. This expanding D3 area was based mostly on SPI at EDDI at various time scales. Soil moisture remains below the 5th percentile for much of North Dakota. Based on snow water content running near average and 6 to 12 month SPIs, D3 was improved by one category across north-central Wyoming. Following multiple changes during the previous two weeks across Colorado, only minor improvements were needed this week. Localized improvements were made to small areas of southern Colorado, based in part on WYTD (since Oct 1, 2020) precipitation.


Midwest

Widespread precipitation (1 to 2.5 inches) fell throughout much of the central and eastern Corn Belt. Abnormal dryness (D0) and moderate drought (D1) were decreased in spatial coverage across Illinois and Indiana. Despite this rainfall during late March, soil moisture (below the 20th percentile) and SPIs at various time scales support maintaining D1 across parts of northern Indiana, northern Ohio, and lower Michigan. Northeast Illinois and eastern Indiana missed out on the heavier rainfall during late March, prompting a slight expansion of D0 for these areas. Also, D1 was added to northeast Ohio based on increasing 90-day precipitation deficits, 90-day SPIs, and soil moisture below the 20th percentile. A 1-category improvement was made to eastern Minnesota and western Wisconsin where more than 1.5 inches of rainfall occurred this past week. 1 to 2 inches of rainfall resulted in a reduction in D0-D2 across central Iowa. However, SPIs dating back 9 months continue to support D2-D3 long-term drought for northwest Iowa.


Northeast

Mostly dry weather (less than 0.5 inch) prevailed across northwest Pennsylvania where abnormal dryness (D0) was expanded. Based on 60 to 90-day SPIs, low 28-day average streamflows, and soil moisture below the 20th percentile, moderate drought (D1) was added to parts of northwest Pennsylvania and adjacent areas of western New York. Increasing short-term precipitation deficits along with a number of low 28-day average streamflows support the addition of D0 across western Maryland and parts of West Virginia. Despite the 1 to 1.5 inches of rainfall this past week across southern New England, lower streamflows supported an expansion of D0 across parts of Massachusetts and southern New Hampshire.


South

On March 23 and 24, heavy rainfall (more than 5 inches) resulted in a 2-category improvement to southeast Louisiana where soil moisture is currently above the 70th percentile. However, much less rain fell across northern Louisiana where an expansion of D0 (abnormal dryness) and D1 (moderate drought) was made. The recent heavy rainfall also led to elimination of abnormal dryness (D0) across the Mississippi Gulf Coast. Heavy rainfall triggered flooding across much of Tennessee during late March and the small areas of D0 were removed from the state. Additional improvements from the previous two weeks continued across the Texas Panhandle, while mostly dry weather and increasing precipitation deficits along with worsening soil moisture conditions resulted in expansion of D1 (short-term moderate drought) across parts of southeast Texas. Soil moisture rapidly declines from east to west across Texas.


Southeast

A second severe weather outbreak during March occurred across Alabama and Georgia on the 25th, with numerous tornado reports and locally heavy rainfall. A 1-category improvement was made to areas that received more than 1.5 inches of rainfall including southern Alabama, the western Florida Panhandle, and parts of northern Georgia. D0 (abnormal dryness) was maintained for parts of eastern Alabama and northern Georgia where rainfall was lighter this past week, and based on 60-day SPIs. Increasing short-term precipitation deficits and low soil moisture conditions support the addition of D0 across the Shenandoah Valley in Virginia, extending northward to southern Pennsylvania. D1 (short-term moderate drought) was introduced to southern Palm Beach County in south Florida, based on 60-day SPI and soil moisture. The D1 areas currently designated for south Florida are consistent with the latest Keetch-Byram Drought Index. The D0 in central Florida was expanded slightly westward this week.


West

Widespread extreme (D3) to exceptional (D4) drought continues to be focused across the Southwest. According to the USDA (for the week ending March 28), nearly two-thirds of the winter wheat is rated as very poor in New Mexico. As of March 27, snow water content is running near 70 percent of average for the Sierra Nevada Mountains. Due to this snow water content along with WYTD (since Oct 1, 2020) precipitation deficits, long-term drought persists for nearly all of California. Since precipitation averaged below normal during March, the impact type was adjusted to include both long and short-term drought for California, along with parts of the Southwest. Based on SPIs at various time scales, D1 (moderate drought) was slightly expanded across north-central Montana while below average snow water content prompted an increase in abnormal dryness (D0) for northwest Montana. To the west across eastern Washington, below average precipitation during March and drying topsoil prompted an expansion of D0 and D1 (short-term moderate drought).


Looking Ahead:

During the next 5 days (April 1 to 5), much drier weather is forecast for the eastern and central U.S. in the wake of a cold front. Mostly dry weather is also expected for the western U.S. with light precipitation limited to the Pacific Northwest and northern California. A brief period of below normal temperatures are forecast for the eastern U.S. and Gulf Coast States. A freeze may affect areas as far south as the Tennessee Valley and southern Appalachians from April 1 to 3. Meanwhile, a rapid warming trend is likely over the northern and central Great Plains with much above normal temperatures forecast during the first week of April.

The CPC 6-10 day extended range outlook (valid from April 6 to 10) favors above normal temperatures across the central and eastern U.S. with the largest probabilities centered over the central and southern Great Plains. Below normal temperatures are most likely along the West Coast and throughout Alaska. Probabilities of below normal precipitation are elevated from the Southeast westward to the southern Great Plains and southern Rockies. Near to above normal precipitation is favored for the Corn Belt, northern Great Plains, much of the western U.S., and Alaska.


Author: Brad Pugh, NOAA, CPC

Dryness Categories
D0...Abnormally Dry...used for areas showing dryness but not yet in drought, or for areas recovering from drought.

Drought Intensity Categories
D1...Moderate Drought
D2...Severe Drought
D3...Extreme Drought
D4...Exceptional Drought

Drought or Dryness Types
S...Short-term
L...Long-term