Mountain Weather Forecast

Weather Synopsis for Monday night through Wednesday

A dying front is draped form about the Columbia River to around Bellingham on Monday afternoon, bringing light to occasionally moderate rain to the Olympics and Mt. Baker areas and clouds to most other areas. Some light rain and snow is expected to linger into the early evening hours on Monday, but conditions should generally dry out, leaving cloud cover. A stronger frontal system moves into the near-shore waters after midnight, spreading light rain and snow to the region primarily after midnight. A mild air mass remains in place west of the Cascade Crest through the evening hours, with cool air to the east, continuing to funnel through the passes. The approaching system should bring moderate winds and rapidly lowers snow levels as frontal precipitation moves in.

The frontal rain band progresses quickly through the Cascades during the morning hours with a slight let-up likely mid-day, then the trough moving onshore re-inforces moderate to heavy precipitation and moderate to strong winds on a SW flow during the afternoon and evening hours and then westerly overnight. With Mt. Baker stands to pick up around 2" of snow water equivalent by Tuesday morning, while the Cascade Passes should wring out the majority of their moisture Tuesday night as the flow turns more westerly. We expect wet snow or perhaps a rain-snow mix at times at Snoqualmie Pass on Tuesday to limit snow accumulations at pass level, but expect significant accumulations in all areas Tuesday night.

While post-frontal precipitation keeps going in the North Cascades on Wednesday, a well-defined and reasonably strong warm front reaches the coastline by early afternoon and the SW Washington Cascades by the evening hours, bringing significant warming and a shot of precipitation.