Mountain Weather Forecast

Weather Synopsis

We're in for a wet and wild next 36 hours as a potent winter storm takes aim at the Pacific Northwest. This system has it all: moderate to heavy precipitation, warming temperatures, and very strong and gusty winds. Expect stormy conditions with periods of heavy rain/snow and low visibility. 

The first bands of precipitation out ahead of the warm front are just starting to make their way across the Puget Sound this afternoon. Nearly all mountain weather stations already show a slow but steady rise in temperatures. Rain and snow will increase across the Olympics and west slopes of the Cascades Tuesday night. As temperatures continue to warm, the snow-rain line should quickly jump above Snoqualmie Pass during the evening hours. Strong westerly winds will help push showers east of the Crest, but it won't be until Wednesday that the bulk of the moisture ventures over the mountains.

The storm continues to intensify Wednesday morning as the jet stream passes overhead and the upper air flow turns more southwesterly. This setup draws a deep moisture tap from out in the Pacific Ocean and develops an atmospheric river. Warmer air continues to push into the region and finally makes its way east of the Cascades. Stevens and White Passes should see rain at road level around lunchtime. Very strong to extreme winds accompany moderate to heavy precipitation throughout the day. 

The frontal feature deepens southward Wednesday night as the storm continues to rage. This focuses a bit more of the precipitation on the southern volcanoes. As the storm moves into Oregon, colder air floods into the area, and snow levels quickly fall. Expect snow below all pass levels before sunrise. As the bulk of the storm exists Thursday, post-frontal showers and an unstable atmosphere should help wring out additional snow, mainly along the west slopes of the Cascades.