This week’s drought summary
The upper-level circulation over the contiguous U.S. (CONUS) during this U.S. Drought Monitor (USDM) week (May 24-30) was dominated by three features: a trough over the West, a ridge that extended from the southern Plains to the Great Lakes, and a cutoff low over the Southeast. This pattern resulted in targeted areas of precipitation, some of it heavy, while large parts of the CONUS received little to no precipitation. Pacific weather systems moved across the West, but their fronts stalled out when they ran into the ridge over the Plains. The northwesterly flow associated with the trough inhibited precipitation across parts of the West, so the week was wetter than normal only from the Great Basin to northern Rockies. A southerly flow over the Plains was created between the western trough and eastern ridge. This flow funneled Gulf of Mexico moisture across the Plains. The moisture fed thunderstorms and weather complexes that developed along the stalled-out fronts and dry lines, resulting in above-normal precipitation across western portions of the Great Plains from Texas to Montana. Several inches of rain fell with some of these thunderstorms, resulting in localized flooding. The ridge inhibited precipitation, so a large part of the country from the Mississippi River to the Northeast received little to no precipitation. The exception to this was the Southeast, where the cutoff low pulled in Gulf and Atlantic moisture to spread above-normal precipitation across much of Florida and the Carolinas to Appalachians. Weekly temperatures averaged cooler than normal from the southern Plains to East Coast, but they were warmer than normal across the northern Plains and northern parts of the West. Abnormal dryness or drought spread across a large part of the Midwest and Northeast, and in parts of the Pacific Northwest, Puerto Rico, and Hawaii. Drought or abnormal dryness contracted across the Florida peninsula, across large areas in the western Great Plains, and in northwest Puerto Rico.
South
Western parts of the South region were wet, while eastern parts were mostly dry. Extreme eastern Tennessee received some rain from the Southeast’s cutoff low, but dry conditions dominated across Arkansas, Louisiana, Mississippi, and Tennessee. D0 expanded in parts of these states. Heavy rain inundated parts of western Texas and Oklahoma, causing contraction of abnormal dryness and moderate (D1) to exceptional (D4) drought. Over 5 inches of rain was recorded at several stations in the Texas panhandle. Soils were wet, streamflow was high, and 6-month precipitation deficits were erased across much of the Texas panhandle. D3 (extreme drought) expanded in Oklahoma just east of where it rained. May 28 USDA data revealed 40% of the winter wheat crop in Texas was in poor to very poor condition.