Mountain Weather Forecast

Weather Synopsis

A shortwave upper trough and tightening surface low move into the waters off the Oregon Coast late Thursday. Radar echoes indicate a well-developed shield of moisture spinning moving into western Washington and Oregon Thursday afternoon. Despite the gradual weakening of the low, the increasingly compact system could crank out significant snow totals through mid-day Friday. Precipitation will focus to the north of the low center with a tight band of moderate to heavy rain and snow from the central Washington Cascades southward. Cool air east of the Cascade Crest combined with light E low-level flow should keep precipitation frozen at the passes. The E flow will also enable significant snowfall east of the Cascade Crest. Strong ridgeline winds wrapping around the compact low center will focus on Mt. Hood Thursday night, easing slightly on Friday.

Rain and snow taper and end from north to south on Friday as the shortwave trough slides ashore and flow switches westerly. Westerly flow allows temperatures to moderate along the east slopes of the Cascades. Significant snowfall should be mostly confined to Mt. Hood during the daylight hours Friday. Storm total snowfall should be in the 4-12" from the mountain loop from the Mountain Loop southward, with higher totals possible on the southern volcanoes. Higher snow levels further south in the range may limit lower elevation snowfall for Mt. Hood north to Mt. Rainier.

Friday afternoon, expect low clouds to remain banked against the west slopes of the Cascades with more sunshine east of the Cascade Crest as cool WNW flow spills over a weak offshore ridge. Expect little change in the pattern with generally an inch or less of snow in weak convergence over northern Washington Friday night into Saturday.