Mountain Weather Forecast

Weather Synopsis for Thursday night through Thursday

We're approaching the end of a Pacific Northwest cold air outbreak. Several warm frontal passages have reduced the chance of lowland snow in most areas as temperatures hover in the 30's and 40's throughout the Puget Sound region, with the exception of northern Watcom County where moderate Fraser River outflow continues to keep temperatures below freezing.

The cold, deep Canadian low dominating our weather pattern which has been providing us with a dome of modified arctic air that has been spilling into the region through the Fraser River gap has merged with a low near the northern tip of Vancouver Island. This cold, offshore trough should increase light snow showers across the region as it moves over the forecast area, flattening slightly with a moderate ridge moving into the near-shore waters. 

Light snow showers should decrease Friday morning as the trough shifts east and a warm frontal boundary begins to lift northward ahead of the next system, bringing light snow to the Mt. Hood and South Washington Cascades late in the day. Expect cold temperatures (but not as cold as earlier in the week) for Thursday night and Friday, with a warm front moving into the region, bringing increasing light snow up to the Mt. Rainier or possibly Snoqualmie Pass area by the end of the day. The warm front should also bring a switch to E flow through the passes as the precipitation moves into the region, with a strong low progressing rapidly ENE, about 1000 miles offshore.

Friday night, the warm front lifts north slowly across Washington State overnight, spreading light snow with ESE winds focusing some enhancement of light to moderate snowfall on the E slopes of the Cascades. This warm front will bring rapidly warming temperatures to the west of the Cascade Crest, resuming our more traditional programming of mountain snow and lowland rain. A cold front brings a band of moderate to heavy rain and snow to the coast and Olympics by the early morning hours. Moderate E winds gusting strong through the mountain gaps and foothills, with the peak winds early Saturday morning as the frontal system moves into the Cascades. The frontal passage may or may not result in a brief switch to W wind late Saturday. The volcanoes (Paradise and Baker) are likely to bet around a foot of snow Friday night through Saturday with 6-12" expected for Snoqualmie, Stevens, and Hurricane Ridge.