Mountain Weather Forecast

Extended Weather Synopsis for Friday night through Friday

The shortwave trough on strong NW flow will slide down the British Columbia coastline into Washington State by mid-day, bringing moderate rain and snow with gradually rising snow levels ahead of a surface frontal passage in the late afternoon hours. A changeover to rain at Snoqualmie Pass likely during the late afternoon hours before changing back to snow as temperatures cool behind the front. Precipitation is likely to remain all snow at Stevens Pass. Northwest flow will continue behind the front and snow showers will decrease Friday evening, with heavier amounts in convergence. Crest-level winds Friday and Friday night will be moderate to strong at times.

A stronger storm system and upper shortwave trough embedded into the larger continental-scale trough covering much of Canada will ride down the back-side of the offshore ridge tracking along the British Columbia coastline once again, with the surface low currently forecast to track over Vancouver, BC. This northward track allows the storm system to bring some rising freezing levels as it as a warm front will pass over the forecast area on Saturday morning and a cold front will cross the area Friday afternoon. During this warm-up, Snoqualmie Pass could once again see a changeover to rain for a period of time before changing back to snow, while Stevens Pass is likely to stay snow at pass level. This system will spread moderate to heavy precipitation late Friday night through the evening hours on Saturday, with light to moderate snow showers continuing from Snoqualmie Pass southward through Sunday as the surface and upper low sits and spins over Washington State on Sunday. As the low moves east late Sunday, the northerly flow will bringing modified arctic area to most our forecast area and likely the coldest area of the season to date.