NOAA's National Centers for Environmental Information
Approximately three percent of the contiguous U.S. (CONUS) was covered by snow at the beginning of November according to NOAA's National Snow Analysis. The highest elevations of the Sierras, Rockies and Cascades as well as portions of the central High Plains and northern Great Lakes received late-October snowfall that remained on the ground at the beginning of the month. By mid-month, a powerful low pressure system swept across the northern Plains, Great Lakes and parts of the Northeast, bringing cold air, snow and strong winds, which fueled lake effect snowfall downwind of the relatively warm Great Lakes waters. By the 15th, 14 percent of the CONUS was blanketed by snow — the maximum extent for the month. In the ensuing days, temperatures warmed and snowdepth waned with only small amounts of additional snow falling across portions of the Great Lakes and Northeast, primarily driven by lake effect winds. By the end of the month, approximately 11 percent of the CONUS was covered by snow, in the highest elevations of the western mountains and from North Dakota to the Great Lakes and into New England. Overall, November snow cover across the CONUS was the third-lowest extent on record. This was the result of an extremely dry month across the CONUS (eighth driest on record) and relatively warm temperatures spanning locations that climatologically favor November snowfall.
According to NOAA data analyzed by the Rutgers Global Snow Lab, the November snow cover extent was about 185,000 square miles, approximately 325,000 square miles below the 1991-2020 average. This was the third-lowest value in the 56-year satellite record. Above-average snow cover was observed across parts of the Northern Tier, Great Lakes and Northeast. Below-average snow cover was observed across much of the western U.S. and Plains states.
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 October 31, SWE values in excess of 150% of median were observed across portions of the northern Cascades, Bitterroots, Sierras, Great Basin and central Rockies. Below-average SWE values existed across portions of the northern Rockies, southern Cascades and southern Rockies. By the end of November, SWE values across much of the western U.S. were less than 75 percent of median with many locations below 25 percent. Above-median SWE values were limited to the northern portions of U.S. Rockies in the Lewis Range.
