Mountain Weather Forecast

Weather Synopsis

A major winter storm is knocking at our door this afternoon. The weather will deteriorate rapidly over the evening hours. Expect extremely stormy conditions with very strong and gusty winds, heavy precipitation, and fluctuating snow levels through at least Monday night. A strong jet stream and associated low-pressure system will take aim at the Pacific Northwest Sunday evening. First up, a warm front will push over the mountains causing southerly winds to increase significantly and moderate to heavy rain and snow. This first round of precipitation will favor sites near the volcanoes. However, when combined with the strength of the overhead jet stream, showers should push into all locations, even east of the crest. Overnight, snow levels will sit near or just above Stevens and White Passes, and fluctuating temperatures may cause the rain-snow line to yo-yo.

The trailing cold front will bear down on our region Monday morning. This will maintain heavy precipitation and very strong and gusty westerly winds. Temperatures will quickly drop over the morning hours, with snow eventually reaching below all Pass levels. With plenty of moisture in place and a very strong zonal jet stream, just because the cold front has passed doesn't mean the action is over. Windy conditions should persist throughout the day with very strong to extreme alpine wind speeds. Similarly, moderate to occasionally heavy post-frontal showers will start to pile up snow in the mountains. Most locations could easily see 1-2 ft of snow, with locations near Mt Baker or Mt Rainier seeing 3 or more feet of accumulation by the storm's end. 

Showers should continue Monday night for most locations especially near and west of the Cascade crest. A high-pressure ridge will start to build into the area Tuesday morning and try to put an end to what's left of the snow showers. Weather models disagree about when the bulk of the precipitation will draw to a close, and small changes in timing could make a big difference. Either way, by Tuesday afternoon, you should see drier weather and maybe even a few sun breaks.