Historic Winter Storm to Impact the Northern Rockies & Northwest

An early early-season winter storm is expected to bring heavy snow and near-blizzard conditions to the northern Rockies & parts of the Northwest this weekend.

A slow-moving, potent upper-level low is pulling in ample Pacific moisture into the Northwest (see Fig. 1). This deep moisture, coupled with an amplified trough (which is providing the cold air out of Canada) will setup this historic winter storm.

Fig. 1: Pacific moisture pulled into the northern Rockies (Tropical Tidbits)

Snow is already beginning to fall in the higher elevations of the northern Rockies and the Washington this morning. The snow is expected to increase in intensity and coverage throughout the day–continuing into Sunday and the snow levels will begin to fall during the overnight hours on Saturday. The local National Weather Service offices have issued Winter Storm Warnings from the Cascades of Washington east into Idaho and Montana. There are also Winter Storm Watches & Advisories surrounding the Winter Storm Warning (see Fig. 2).

Fig. 2: Current winter weather alerts (Pivotal Weather)

Within the Winter Storm Warnings, heavy snow, paired with strong winds will reduce visibilities and impact travel. The heaviest snow can be expected within the Winter Storm Warnings (high elevations of Washington, Montana, Idaho & Wyoming) where over a foot of snow is forecast to fall–much of northern Montana can expect to see widespread, heavy snow of one to three feet. Lesser amounts are forecast for the lower elevations of the Northwest (see Fig. 3).

Fig. 3: NAM snowfall accumulation forecast (Tropical Tidbits)

The snow will begin to taper off for the northern Rockies on Monday. Farther east, the Black Hills of the Dakotas should see rain transition to a rain/snow mixture by late Monday into Tuesday. Light accumulations are possible.

While snow is not rare this early in the season for the northern Rockies, the forecast accumulations of several feet of snow for the highest elevations of the northern Rockies is historic.