Mountain Weather Forecast

Weather Synopsis

The brunt of the atmospheric river continues Tuesday night into the early morning hours on Wednesday as a strong warm front lifts into northern Washington State, followed by a strong cold front moving through from the W early Wednesday.  Snow levels rise to around 7500 ft in most areas (except Washington Pass) as strong SSW winds over-ride cold air in place east of the Cascades with moderate E winds sucking that air through the mountain gaps. But the transition to these elevated snow levels will be particularly messy near and east of the Cascade Crest. A period of heavy freezing rain remains likely during the evening and overnight hours. Snoqualmie Pass likely transitions to freezing rain by 7 PM and Stevens Pass by 10 PM. We don't know whether enough warm air will arrive to displace the cold air at Washington Pass.

The front moves through with strong cooling by 7 AM on Wednesday, cutting off the deluge of moisture. Expect rapid cooling during the morning hours as snow levels drop to around 4000 ft by the afternoon with a push of moderate W winds (potentially locally strong for ridgelines east of the Crest). Light snow showers focus mostly on the northern and central Cascades with convergence likely creating periods of moderate rain and snow for Stevens Pass and the southern mountain loop through the mid-day hours. Expect increasing sun breaks east of the Cascade Crest.

Weak ridging brings dry conditions Wednesday night, but warming associated with an approaching warm front will become evident for Mt Hood and the Olympics.

The warm front brushes NW Washington with light precipitation for the Olympics and N Cascades. Expect a sharp contrast in temperature across the Cascades as E flow keeps the passes and E slopes significantly cooler.