According to today's Drought Monitor report of the U.S. Department of Agriculture (USDA), an upper-level ridge dominated the central contiguous U.S. (CONUS) during this U.S. Drought Monitor (USDM) week (September 14-20). It was bracketed by an upper-level trough which moved out of the Northeast early in the week, and a Pacific upper-level trough that moved into the West as the week progressed.
Pacific weather systems moved across the northern states between the troughs. This pattern resulted in above-normal precipitation across much of the West and parts of the Northeast. Fronts associated with the Pacific systems triggered showers and thunderstorms across parts of the central and northern Plains to Mid and Upper Mississippi Valley.
In the Midwest, two inches or more of precipitation fell this week in a streak across southern Iowa to central Illinois, and over northern parts of the Midwest region. Other areas had up to half an inch of rain, while southern parts (southern Missouri to Kentucky) and parts of the Great Lakes had little to no rain.
D2-D3 contracted in southeast Iowa to adjacent Illinois and northeast Missouri where the heaviest rains fell. D0-D1 contracted in Illinois and D0 shrank in parts of Indiana and Minnesota. But the bigger change was expansion of drought in several Midwestern states. D0-D3 grew in Missouri, D0-D2 expanded in Minnesota and Wisconsin, and D0-D1 expanded in parts of Michigan and Illinois.
For the full USDA report for Sept. 22, click here.