Cold air moved through the central and eastern U.S. this week as storm systems farther south brought locally heavy rain and snow from the Lower to Mid-Mississippi Valley on the western end to the Mid-Atlantic coast in the east, improving drought conditions in some areas, according to this week's U.S. Drought Monitor.
The precipitation mostly missed the immediate Gulf of Mexico coastal areas, where drought expanded. The week was drier than normal in the Pacific Northwest and much of the Intermountain Basin, where drought expanded.
This week's drought map author Richard Heim explains:
Northeast/Mid-Atlantic. Much of the Northeast and Mid-Atlantic remained buried under a foot or more of snow. Rivers remained frozen, lowering streamflow measurements in some areas to very low levels.
A few coastal stations reported precipitation amounts of an inch or more for the Drought Monitor week, but precipitation was generally below normal in the Northeast. D0 was trimmed in southern West Virginia and adjacent Virginia, but the map depiction remained unchanged across the rest of the region.
The Northern Plains and Midwest. Most of the Central to Northern Plains and Upper Midwest were drier than normal this week, with some areas receiving no precipitation.
Precipitation deficits in the Northern Plains to Upper Mississippi Valley continued to mount, exceeding 4 inches over the past 6 months in parts of the Dakotas and Minnesota. The drier-than-normal autumn depleted soil moisture, leaving potential spring moisture concerns. The current depiction of D0-D1 adequately represents this situation.
To the south, a major winter storm moved across the Tennessee and Ohio Valleys, dumping an inch or more of precipitation, mostly in the form of snow, across a wide area.
The precipitation raised stream levels, replenished soil moisture, and erased precipitation deficits for the last 30 days. As a result, D0-D1 were pulled back in Kentucky and the Missouri bootheel.
Significant deficits remained at the 60-90 day time scale, so areas of D0 and D1 remained to represent these longer-term conditions.
Southern Plains/Southeast. A major winter storm system moved across the Lower to Mid-Mississippi Valley and Southeast during the middle of the Drought Monitor week, followed by another system at the end of the week which moved out of the Southern Plains and across the Southeast.
These systems left a total of 1-3 inches of precipitation across an area stretching from northeast Texas to the Carolinas, with locally 3-5 inches in parts of Tennessee and northern Mississippi, replenishing soil moisture and filling streams.
D0-D2 contracted in Tennessee, northern Mississippi, and adjacent Arkansas. A remnant of D1 remained in western Tennessee, and D1-D2 remained in northeast Arkansas, to reflect the continued significant precipitation deficits which remained over the last 3 to 5 months.
D1 expanded from southern Louisiana to southern Alabama and the Florida panhandle where weekly precipitation was below normal and deficits continued to mount.
In Texas, above-normal precipitation at the 7-day to 6-month time scales prompted the pullback of D2-D3 in the northwest corner of the panhandle, while D2-D3 expanded in south-central Texas.
Deeper soil moisture, stock ponds, rivers, and reservoirs in western Oklahoma have never fully recovered from the drought which began four years ago.
NASA satellite-based measurements of groundwater indicated severely dry conditions in western Oklahoma. D3 was expanded in western Oklahoma to better reflect long-term moisture deficits as well as record low streamflow levels.
D1-D3 were expanded in north central Oklahoma, and D1 in adjacent south central Kansas, where 7-day to 6-month precipitation deficits were greatest and surface water supplies continued to be a concern.
West. It was another dry week for much of the West, with parts of the Pacific Northwest, Northern California, Arizona, New Mexico, and the Intermountain Basin receiving no precipitation.
In California, D4 was pulled back in some areas, but otherwise the state remained locked in a years-long drought.
Mountain snowpack remained well below normal, not just in California but all across the Cascades, Sierra Nevada, and Intermountain Basin.
D1 expanded along the southern Cascades of Washington, and was added to the Olympic Mountains, to reflect the low snowpack. D1-D3 expanded in southwest Idaho to reflect basin impacts. D0 expanded in southeast Idaho and into southwest Montana and northwest Wyoming (in the vicinity of Yellowstone National Park) where streamflow levels, snow water content, and water-year-to-date precipitation were low.
D1 expanded across southwest Utah, D0-D1 expanded in northeast Utah into southwest Wyoming, D2 expanded in northwest Utah, and a spot of D3 was added to northwest Utah.
Read the complete recap on the U.S. Drought Monitor website
Source: Richard Heim/The U.S. Drought Monitor is produced in partnership between the National Drought Mitigation Center at the University of Nebraska-Lincoln, the United States Department of Agriculture, and the National Oceanic and Atmospheric Administration.