According to the October 17, 2017, U.S. Drought Monitor, moderate to exceptional drought covers 12.5% of the contiguous United States, a decrease from last week’s 14.1%. The worst drought categories (extreme to exceptional drought) also decreased from 1.1% last week to 0.8%. Exceptional drought was completely eliminated from the Lower 48 this week.
The main atmospheric circulation pattern continued to be an upper-level trough over the western contiguous United States and an upper-level ridge over the East. But during this week, weather systems moved through this pattern, dragging fronts and low pressure systems with them. The temperature anomaly pattern followed the upper-air pattern, with warmer-than-normal temperatures beneath the eastern ridge and cooler-than-normal temperatures in the West beneath the long-wave trough.
The fronts and low pressure systems brought precipitation to parts of the West, much of the Midwest to Great Lakes, and parts of the Plains and East Coast. The weather systems missed the Southwest and much of the Plains and New England, where little to no precipitation fell. Drought and abnormal dryness contracted in the Northwest, Northern Plains, and Midwest but expanded across parts of the Southern Plains to Northeast.
Abnormal dryness and drought are currently affecting over 126 million people across the United States—about 40.6% of the country’s population.