A slow-moving surface cold front passing southeastward through the northwestern U.S. ahead of a potent upper-level trough brought 6 to 12 inches of snow across parts of the northern West yesterday. The heaviest amounts were in northwestern Wyoming. Little snowfall or rain occurred in the rest of the coterminous U.S. yesterday.
Cold surface air behind the Western U.S. cold front caused the snowpack across the West to become cool to cold, and little snowmelt occurred there yesterday. In the Southern High Plains, warm conditions continued, and moderate snowmelt occurred there. Slow to moderate snowmelt also occurred in Michigan and at the lower elevations of the Appalachians. Moderate sublimation continued in the Southwest, and blowing snow sublimation occurred in parts of the High Plains due to continued strong surface winds.
The upper trough will be the main weather-maker for the coterminous U.S. during the next four days. It will move slowly southward to be over the Southwest by Saturday and remain there for a couple of days. Cold surface air behind an arctic cold front, currently across the southern Plains, will remain in place and will be reinforced on Sunday by another batch of cold air from Canada. The cold front on the leading edge of the cold air will become stationary today from central Texas through the Northeast, and disturbance rotating around the base of the trough will provide upper-level energy, while Gulf moisture streams northward.
Today, the heaviest snowfall is expected in Colorado as a surface high near the Four Corners moves slowly eastward. While surface moisture will be moderate, strong surface winds will cause up to 1 foot of upslope snow to mainly Colorado and northern New Mexico, with light snow likely in the higher elevations and latitudes of Arizona. Ahead of the snow near the front, an extend period of freezing rain will occur, mainly from north and northwest Texas northeastward through Missouri today and tomorrow, and extending northeastward to southern Lower Michigan by Sunday. Also on Sunday, a large piece of upper-level energy is expected to leave the Southwestern trough and move northeastward toward the lower Great Lakes. This will bring 4 to 10 inches of snowfall from Kansas to southern Wisconsin through Monday. By then, the upper-level trough is expected to start shifting eastward, bringing snowfall to the Great Lakes and Northeast and freezing rain and heavy rainfall to the southeastern U.S. on Monday.
weather.gov
