Mountain Weather Forecast

Weather Synopsis for Wednesday & Friday

On Wednesday, the Pacific Northwest continues to sit between a robust and relatively stationary high pressure off the northern coast of California and a deep low over Hudson's Bay. The jetstream lies to our north, taking today's storm track and precipitation on a higher-latitude trajectory than previously expected. The resulting weather has been warmer than anticipated for Wednesday, with relatively drier weather. Winds have been and will continue to be moderate to strong on the east slopes of the Cascades at higher elevation and downslope winds to the east of the Cascades have scoured out the cold pool that normally resides there. Mazama saw an 18F jump in temperature in just one hour this morning due to a wind shift from E to W and temperatures are now in the mid-50's. Winds below crest-level have been light to moderate.

To the west of the Cascade crest the atmosphere has been very stable on Wednesday morning, meaning that the temperature doesn't decrease significantly with height as you normally expect. Temperatures are in the low-to-mid 30's at most NWAC stations, including Camp Muir!

Light precipitation is beginning to re-develop in the Northwest Cascades this afternoon with light amounts expected. Some locations in the central and north Cascades (west slopes) have also experienced freezing rain above 5000 feet or drizzle. 

As a system approaches from the W-NW tonight, W-SW winds will increase to the moderate-to-strong range by morning at crest level and snow levels will begin lowing slightly as the jetstream drops southward, pushing the ridge back south. In some cases east of the Cascade crest, winds will be very strong tonight.

On Thurday, the reasonably strong, but relatively moisture-starved surface cold front associated with a short-wave trough will cross the Pacific Northwest, arriving in the Olympics in the early morning, then the NW Cascades around 10 AM and reaching Mt. Hood during the evening hours.

Snow levels will drop significantly behind the front with rain changing back to snow at many mid-elevation locations between 1-4PM at the Mt. Baker base and between 4 and 7 PM for Stevens Pass and Crystal Base, with a changeover at Snoqualmie pass level likely after 7 PM. Most precipitation will be with moderate post-frontal showers behind the cold front and a potentially strong convergence zone that is likely to set up in the Stevens Pass vicinity during the afternoon and early evening hours.

Some lighter convergence will focus lingering snowfall in the Snoqualmie Pass vicinity on Thursday night.