The weather pattern has been undergoing a shift over the past several days to colder temperatures across the Rockies, which is a change from most of the winter up to this point which has been unseasonably warm for all but northern Montana. High pressure is shifting farther west just off the west coast, which is allowing for colder Canadian airmass intrusions into the Rockies, along with a more active storm track. While the strong ridge of high pressure off the Pacific coast will continue to act as a barrier to storm systems with deeper moisture, the active pattern with frequent low pressure systems from the northwest will continue to bring frequent snow chances to the Rockies over the next week, and likely through the end of the month. Depending on the individual storm tracks, some of these systems will occasionally bring snow to areas east of the Continental Divide as well.
The map below shows NOAA’s climate prediction center probabilistic snowfall forecast for the next 72 hours. The 50th percentile range indicates the “most likely” range of snowfall over geographic areas, and paints a general picture of which areas will be favored for the most snowfall over the next 3 days.
The low pressure system will be moving into Northwestern U.S. tonight through Wednesday, resulting in locally heavy snowfall amounts across the Washington Cascades, Idaho Panhandle, and Northwest Montana. Strong winds expected along the eastern slopes in Glacier National Park have even prompted a blizzard warning as this storm arrives. The track of this system will continue to move toward the southeast Wednesday night into Thursday, bringing good snow to the Tetons of Wyoming and eventually the Colorado Rockies.
The snow will be beneficial to the mountains of Colorado where snowpack has been below average, but notice how other areas hurting for snow this winter will not be favored in this pattern, such as California, and to a lesser extent Utah. This is due to high pressure just off the California coastline acting as a barrier, and resulting in a storm track that will be missing these areas to the north and east.