Weather Summary: For the second week in a row, beneficial showers peppered the East. Much-needed rain also fell across the northern Plains and upper Midwest, although amounts were highly variable. In contrast, “flash drought” conditions quickly worsened across the remainder of the Midwest, portions of the central and southeastern Plains, and the Mid-South. The term “flash drought” describes a period of short-term dryness, often accompanied by above-normal temperatures, which has an adverse impact on crops and pastures. Elsewhere, much of the West—excluding the northern tier of the region—continued to slip deeper into drought under a warm, mostly dry weather regime.
The East: Once again, appreciable rainfall from the Mid-Atlantic States into southern New England chipped away at dryness (D0) and moderate to severe drought (D1 to D2). Despite some lingering year-to-date rainfall deficits in locations such as Washington, D.C., drought impacts were quickly diminishing. Through May 22, Washington’s year-to-date precipitation stood at 9.87 inches (67% of normal). Farther south, a core region of extreme to exceptional drought (D3 to D4) lingered across central and southern Georgia, northern and central Florida, southern South Carolina, and southeastern Alabama. On May 19, the first Atlantic tropical storm of the season, Alberto—the earliest named system since Andrea on May 9, 2007—formed about 120 miles south of Cape Fear, North Carolina. The storm was compact and remained offshore during its entire lifespan, resulting in negligible impacts other than contributing to an increase in convective activity along the southern Atlantic Coast.
The Mid-South: Rapidly deteriorating agricultural conditions resulted from another week of very warm, mostly dry weather. During the week ending May 20, the portion of pastureland rated in very poor to poor condition increased by at least 8 percentage points in Arkansas (from 11 to 23%) and Missouri (10 to 18%). During the same 7-day period, USDA reported that the portion of topsoil moisture rated very short to short skyrocketed from 41 to 66% in Arkansas and 23 to 57% in Missouri. As a result, moderate to severe drought (D1 to D2) expanded in an area centered on the northern Mississippi Delta and the lower Ohio Valley.
The Midwest: For the week ending May 20, the portion of topsoil moisture rated very short to short jumped at least 20 percentage points in Iowa (from 9 to 44%), Indiana (15 to 43%), Illinois (12 to 33%), Michigan (7 to 32%), and Wisconsin (6 to 30%). As a result, there was a fairly large expansion of abnormally dry conditions (D0) across the central and eastern Corn Belt. Hot weather, short-term dryness, and crop demands were to blame for the rapid depletion of topsoil moisture. On May 18, high temperatures soared to daily-record levels in St. Cloud, Minnesota (94°F), and Eau Claire, Wisconsin (91°F). The following day, May 19 featured daily-record highs in Michigan locations such as Traverse City (92°F) and Alpena (91°F). In contrast, showers developed across the upper Midwest. Although upper Midwestern rainfall coverage was patchy, drought development was arrested in some areas. Little rain fell, however, east of a line from southeastern Nebraska to Lake Superior.