According to the June 29, 2021, U.S. Drought Monitor, moderate to exceptional drought covers 39.5% of the United States including Puerto Rico, a decrease from last week’s 39.9%. The worst drought categories (extreme to exceptional drought) increasedfrom 18.2% last week to 19.0% this week.
This week began with an upper-level ridge over the western contiguous United States and a trough over the east. The week ended with the eastern trough migrating out of the country, being replaced with an East Coast ridge, and the ridge in the West amplifying into a powerful “Omega block.” An upper-level trough became trapped over the central contiguous United States between the western and East Coast ridges. The western “omega ridge” kept the western contiguous United States dry and brought record heat to the Pacific Northwest and southwestern Canada. The ridge in the East inhibited precipitation, with much of the country from central Texas to New England having a drier-than-normal week.
Cool and dry Canadian air masses were slow to move out of the East, leaving much of the Tennessee Valley to East Coast with a cooler-than-normal week. Later, Canadian cool fronts slipped into the central contiguous United States and stalled out between the two ridge systems. The circulation around the East Coast ridge blew Gulf of Mexico moisture into the central contiguous United States. The moisture fed showers and thunderstorms that developed along the stalled-out fronts, resulting in above-normal precipitation across much of the Southwest, southern and central Rockies, and western Texas to the Great Lakes. Drought and abnormal dryness contracted from western Texas to the Great Lakes, along the path of the frontal rains, and a few other parts of the Upper Midwest, Florida, and Puerto Rico.
Drought or abnormal dryness expanded or intensified in the Pacific Northwest to northern Plains and parts of New England, the Mid-Atlantic states, and Hawaii. Contraction exceeded expansion, so the nationwide moderate to exceptional drought area decreased this week.
Abnormal dryness and drought are currently affecting over 123 million people across the United States including Puerto Rico—about 39.7% of the population.
In addition to Drought.gov, you can find further information on the current drought as well as on this week’s Drought Monitor update at the National Drought Mitigation Center.
The most recent U.S. Drought Outlook is available from NOAA’s Climate Prediction Center and the U.S. Department of Agriculture provides information about the drought’s influence on crops and livestock.