The U.S. Drought Monitor week ending March 17 saw another round of winter storms, bringing above normal precipitation to parts of the northern High Plains, Southwest, southern plains, and Tennessee Valley. Many areas recorded totals that exceeded 200% of normal over the seven-day period, leading to improvements to areas of abnormal dryness and drought in areas where the excess moisture erased deficits and improved soil moisture and streamflow. Once again, precipitation over the Northwest and Gulf Coast states was below normal with most areas having received less than 50% of their normal amount over the last 30 days. The lack of precipitation, combined with warmer than normal temperatures, led to expansions in pockets of abnormal dryness and drought.
While much of the northeast received precipitation last week, totals in southern and coastal New England continued to be below normal, further contributing to deficits of 6-plus inches over the last 90 days. The lack of rain and snow combined with unseasonable warmth – with many stations reporting mean temperatures in the top five on record over the last month, low streamflow values, and low groundwater levels -- led to the introduction of a swath of D0 (abnormal dryness) from eastern Massachusetts southward to northern New Jersey. According to local media reports, the dry conditions combined with high winds contributed to brush fires in eastern Massachusetts, Rhode Island, and southeast New York.
The general pattern of rain in the northern tier of the region and dry weather in the south continued again last week. Much of the Tennessee Valley and Southern Appalachia received amounts in the range of 0.5 to 3 inches, while regions near the Gulf coast had little to no rainfall. Changes to this week’s map include small expansions of D0 (abnormal dryness) in southern Alabama, the extreme western Florida Panhandle, and the central and southern Florida Peninsula as rainfall shortages in these have reached about 3 to 4 inches over the last 30 days, drying soils and lowering streamflow. Should they miss out on next week’s forecast rainfall, areas to watch for deteriorating conditions include Virginia and northern North Carolina where moisture deficits are beginning to build.
Last week, a band of heavy rainfall fell across the northern half of the region, extending from West Texas to western Tennessee with amounts ranging from 1 to more than 4 inches (equivalent to more than 300% of normal in some locations). In southwest Oklahoma and northeast Texas, the excess moisture erased short-term precipitation deficits and recharged streamflow leading to reductions in D0 (abnormal dryness) and D1 (moderate drought). Additionally, the "S" was removed from the "SL" drought designation to indicate that drought and dry conditions are now only present at timescales longer than six months. With over an inch of rain falling after the close of the Drought Monitor week (Tuesday, 8:00 AM EDT) and more expected on the way, additional reductions may take place on next week’s map. Other areas seeing improvements include West Texas with reductions to D0 and D1. Unfortunately, the rain missed the parts of south Texas that need it most and conditions continued to deteriorate, resulting in expansions to ongoing areas of abnormal dryness and drought and the introduction of D4 (exceptional drought). Supporting data include rainfall deficits of 2 to 8 inches (25 to 50% of normal) over the last six months combined with mean temperatures consistently ranking in the top 10 warmest over the same time interval. The combination of dry weather and high temperatures has dried out soils and stressed vegetation with USDA reporting only 28% of topsoil as adequate for crops in the southeast and 3% in the southwest. Other areas seeing deterioration this week include southwest Louisiana and southeast Mississippi with expansions in D0.
The Midwest remains free of any drought or abnormal dryness. While Missouri and Kentucky saw precipitation totals in excess of 150% of normal, the rest of the region received amounts near or slightly below normal continuing a drying trend that began in February. In general, the relatively dry weather has been welcome, enabling producers to begin field work. Soil moisture and streamflow levels remain high from 2019's record-breaking precipitation and a wet January.
The map's drought depiction is unchanged this week in the High Plains. A winter storm during March 13-14 brought snow to the west and central parts of the region and rain to locations in the south and east. The Black Hills saw the highest totals, reporting from 6 to 12 inches of snow while portions of western and central South Dakota and Nebraska reported several inches of accumulation. Dry conditions continue to persist in the drought and abnormally dry areas in eastern Colorado, western Kansas, and southwest Nebraska where less than 0.50 inches of precipitation (about 50% of normal or less) has fallen so far this month. As we tra