Mountain Weather Forecast

Weather Synopsis

The Pacific Northwest sits under NNW flow aloft with very weak disturbances moving over the region. Low-level onshore flow keeps a 3,000-5,000 ft cloud deck pinned against the west slopes of the Cascades. On Monday afternoon, this cloud deck generally didn't have enough lift to make it into the heart of the Cascades. Meanwhile, afternoon cumulus clouds have formed near the Cascade Crest with light to occasionally moderate W or WNW ridgeline winds pushing this weak convection onto the east slopes of the Cascades. Although the convection dies down overnight, the onshore flow and low clouds remained pinned against the west slopes of the Cascades with little to no expected precipitation. Temperatures will drop into the 30s at most 5,000-ft locales, but are likely to drop below freezing around Washington Pass and in the typically colder valleys of the northern interior Cascades. Breezy conditions on the east slopes of the Cascades will reduce the potential for cooling under the clear skies.

A slightly more organized disturbance is likely to move into the region with some mid-level clouds on Tuesday morning. This should create some filtered sunshine across the region at times, while the same low clouds remain against the W slopes of the Cascades. There's likely just enough lift with this system to produce a few hundredths of an inch of precipitation from Mt Rainier northward to Mt Baker, mainly in the mid-day and afternoon hours as snow levels hover around 5000 ft.

Clouds gradually decrease, and the very light precipitation shuts off Tuesday night as an offshore ridge expands into the region. Expect more sunshine than clouds on Wednesday, but with weak onshore flow, some low cloud is likely in the morning hours for the Puget Sound lowland. Freezing levels rise from Tuesday night onwards, reaching around 8000 ft on Wednesday afternoon.