NOAA's National Centers for Environmental Information
Approximately 22 percent of the contiguous U.S. (CONUS) — the maximum extent for the month — was covered by snow at the beginning of April according to NOAA's National Snow Analysis. At the beginning of the month, snow covered much of the mountainous West and northern Plains, and in northern parts of the Upper Midwest and Northeast. A spring snowstorm brought heavy snow and powerful winds to much of New England from April 2-4, downing trees and knocking out power to hundreds of thousands in the region. Snow cover ebbed and flowed somewhat before decreasing to approximately 4 percent on the 25th of the month — the minimum snow cover extent for the month. Snow covered parts of the mountainous West and northern parts of New England. During the remainder of the month, snow coverage increased steadily to cover parts of the mountainous West and parts of the northern Plains and Upper Midwest. By April 30, snow covered 5.6 percent of the CONUS.
According to NOAA data analyzed by the Rutgers Global Snow Lab, the April snow cover extent was 183,000 square miles of the contiguous U.S., 95,000 square miles below the 1991-2020 average, and the 14th-lowest value in the 58-year satellite record. Below-average snow cover was observed across much of the West and from the northern Plains to parts of the Northeast, while above-average snow cover was observed in small parts of the Sierras and Rockies.
Melting of winter and spring mountain snowpack provides a crucial summer water source across much of the western United States. The total annual water budget for agriculture and human use in the mountainous West is highly dependent on the amount of snow melt that will occur in spring and is proportional to the amount of snow on the ground, which can be approximated by a measure of the snow water equivalent (SWE).
On March 31, SWE values were below normal across northern portions of the West, while central and southern parts of the West observed above-normal SWE values. By the end of April, SWE values were below normal across northern and eastern portions of the West, as well as in parts of Sierras, while parts of the southwestern U.S. observed above-normal SWE values.
