Mountain Weather Forecast

Weather Synopsis

A weak ridge of high pressure over the region on Tuesday splits a broad closed low rotating off the California coast and a sharp trough moving down the west coast of Canada. Shallow cold air continues to stream through the mountain gaps on Tuesday. The models had overrun this shallow cold air too quickly. Temperatures remain in the 30s for most of the Puget sound lowlands while an inversion has persisted in the mountain gaps into the afternoon. This sets the next system up for snow levels that will be lower than the weather models predict (at least to start out) and in some cases may start around sea level in northern Washington State.

The low dropping southward spreads a warm front into northern Washington Tuesday evening, increasing light rain, snow and some freezing rain as warm air continues to move into the region at mid-levels. The system also taps into moisture from the low off the California coast, allowing this precipitation to extend further south. Rain, snow and wind ramp up significantly, resulting in significant snowfall. Expect the most snow to fall in the northern Cascades with 8-12" of snow possible around Mt. Baker, but other areas should pick up 3-8" amounts.

The warm front lifts north of the Canadian border by Wednesday and winds turn SW or SSWerly. This focuses the precipitation increasingly on the Olympic Mountains and the Washington Volcanoes. Expect strong ridgeline wind gusts for these same areas, plus Mt. Hood. East flow will be a wild-card in the forecast until the cold front moves through early Thursday. East flow will at times switch westerly, so Snoqualmie Pass may see rain switch to snow or mixed precipitation and back several times.

The trough moves into the near-shore waters Wednesday evening with the heaviest band of rain and snow moving into the region overnight.

A stiff westerly flow keeps the snow showers piling up on Thursday as snow levels drop to 1500-3000 ft. Expect convergence in some areas.