U.S. Drought Monitor Update for April 9, 2019

According to the April 9, 2019, U.S. Drought Monitor, moderate to severe drought covers 4.3% of the United States, a decrease from last week’s 5.4%. The worst drought categories (extreme to exceptional drought) stayed the same for the third consecutive week—0%.

The atmospheric circulation underwent a shift in the long-wave pattern during this U.S. Drought Monitor week. The week began with an upper-level ridge over the western contiguous U.S. and a trough over the East. The eastern trough shifted east and north out of the eastern contiguous U.S., while the western ridge shifted east and broadened over the central contiguous U.S., with an upper-level trough moving over Alaska.

Canadian air masses over the eastern contiguous U.S. were replaced by milder Pacific air masses, resulting in warmer-than-normal temperatures expanding across the country. Pacific weather systems accompanied the milder air masses. Some brought above-normal precipitation to the Northwest, while others tapped Gulf of Mexico moisture to spread above-normal rainfall across the South, from Texas to North Carolina. The areas in between these two storm tracks missed the rainfall, resulting in below-normal precipitation across the Southwest, much of the central to northern Plains, and from the Ohio Valley to much of the Northeast. The precipitation contracted drought and abnormal dryness in parts of the Pacific Northwest and parts of Texas to the Carolinas, while drought or abnormal dryness expanded in other parts of the South and was introduced in a few spots of Appalachia and the Northeast.

Abnormal dryness and drought are currently affecting over 47 million people across the United States—about 15.2% of the country’s population.