Mountain Weather Forecast

Weather Synopsis

3 PM Update: Edited second paragraph in synopsis to improve clarity. No other changes were made.

An upper-level trough is passing over Washington this afternoon, bringing light showers to many mountain locations, especially west of the crest and I-90 north, along with increasing westerly winds. This activity is becoming a bit more widespread this afternoon as the trough marches east. Precipitation totals are pretty light thus far, and with 5000ft temperatures generally in the low to mid 30s, accumulations up until now will have been relegated to the mid and upper elevations. Even there, daytime totals should be less than a few inches in the most favored zones. This evening, a Puget Sound Convergence Zone will develop and indications are that it will take aim at the Snoqualmie Pass area, with some spillover into Stevens and the West Central. The heaviest precipitation looks to fall between 8 PM and 2 AM, when we expect to see a few inches of snow accumulate at pass level, with perhaps 5-8" up high in the bullseye, as snow levels bottom out at 2500ft overnight. Outside of the convergence zone, precipitation totals are paltry. Winds remain in the light to moderate range with the exception of the East Central, East South, and Mt. Hood, where stronger winds will be felt through midday Monday. 

Things start to dry out on Monday, with some lingering shower activity hanging around the west side, I-90 northward. Elsewhere, sun breaks will become more widespread, especially east of the crest and south, and at the mid and upper elevations. Temperatures will be slightly cooler on the west slopes than east, with 5000ft highs reaching the low to mid 30s, while winds should be generally light to moderate. Dry north to northwest flow continues on Tuesday as a high-pressure ridge builds offshore. We expect plenty of sunshine with moderating temperatures, as freezing levels creep up to 4500-6000ft.