Mountain Weather Forecast

Weather Synopsis

Two of the first three waves of a major atmospheric river event have already impacted the Pacific Northwest. The water amounts are already very impressive across the region. Over the past 48 hours, we've seen 3-4" of water equivalent at Paradise, Snoqualmie, and Crystal, while Mt. Baker takes the crown with over 6" of water. Much of this came as snow at mid and higher elevations through Monday night, but a warm front raised the snow level above all major ski area bases early Tuesday.

Our region is in a slight lull on Tuesday afternoon with moderate to heavy (rather than heavy to very heavy) rain and high elevation snowfall rates between waves. The third and final wave arrives Tuesday evening with rain/snow and snow levels both peaking in the late evening or overnight hours as a strong cold front crosses the region from west to east in the early morning horus, ultimately providing a relief valve to the subtropical firehose. We're expecting another 1-2.5" in many areas with continued strong spillover to the lee of the Cascades. SW winds will also peak in the moderate to strong range before switching westerly and increasing through the passes and along the east slopes of the Cascades behind the front. There's very little cold air left and Washington pass remains the only area with pass-level snow. Washington Pass could see a mix or brief changeover to rain at pass level with the frontal passage. However, the front will also bring strong cooling.

Wednesday should be much cooler with rain and snow showers changing to all snow as moderate to strong W flow brings the colder air mass into the region rapidly. Light to moderate snow showers should decrease and focus on the central Washington Cascades, where they will linger into the afternoon. Stevens Pass and the mountain loop may see locally intense snowfall with convergence bands.

A fairly large ridge builds offshore late Wednesday and moves onshore Wednesday night through Thursday, bringing a cold night followed by significant warming west of the crest. Freezing levels could reach 11000 ft for Mt. Hood. Another cold pool will develop east of the Cascade Crest and E flow should keep the passes relatively cool.