NOAA's National Centers for Environmental Information
During April, below-average temperatures were observed across the East early in the month with above-average temperatures later in the month. In the West, above-average temperatures were observed for most of April, especially in the Northwest, which caused an early melt of the mountain snowpack. Several snow storms impacted the high elevations of the Central Rockies, boosting the end of season snowpack. According to NOAA's National Snow Analysis, at the beginning of April, 13.1 percent of the contiguous U.S. had snow on the ground — the highest terrain in the Cascade and Sierra Nevada Mountains, the Central and Northern Rockies, and far northern New England. The monthly snow cover dropped to 3.8 percent by the 23rd of the month, but a potent storm in the Rockies and Northern Plains boosted the snow coverage to 13.2 percent of the contiguous U.S by the 28th. On the last day of April, 10.7 percent of the nation was snow covered — the highest terrain in the Cascade and Sierra Nevada Mountains and the Central and Northern Rockies.
According to NOAA data analyzed by the Rutgers Global Snow Lab, the April contiguous U.S. snow cover extent was 236,000 square miles, 45,000 square miles below the 1981-2010 average and the 19th smallest in the 50-year period of record. Above-average snow cover was observed for parts of the Great Lakes region, and the Central Plains and Rockies. Below-average snow cover was observed for parts of the Northeast, Northern Plains and Rockies, and the Pacific Northwest.
Melting of winter and spring mountain snowpack provides a crucial 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. As of May 1st, near-to-below average snowpack was observed across much of the Northwest and Northern Rockies. Near-average snowpack was observed across the Sierra Nevada Mountains, with above-average snowpack across the Central Rockies. Record-warmth limited the snowpack across much of Alaska with snowpack totals less than 25 percent of average across central and southern regions of the state.