Mountain Weather Forecast

Weather Synopsis

Throughout the five-day forecast period, a ridge of high-pressure extends up to Alaska and dominates the NE Pacific. A deep trough allows very cold air to spill into the eastern US. The Pacific Northwest sits within a very tight temperature and pressure gradient that is creating a strong jetstream over the region with NW flow along the backside of the ridge.

Wednesday night, clouds should increase ahead of an initial weak perturbation dropping SE. Light to very light snow should develop for the mountains of northern Washington by the morning hours.

On Thursday, light to moderate snow increases for the mountains of Washington as NW flow aloft continues. Mt. Baker stands to pick up the most, perhaps 5-8" of snow by the end of the day. W ridgeline winds should increase into the moderate range by Thursday afternoon and should be strongest along the east slopes of the Cascades.

Thursday night the jetstream lifts northward into British Columbia and reaches (reaching 150 mph plus speeds). Heavy rain and snow should focus on the west slopes of the Cascades and Olympics. The heaviest precipitation will be over northern and central Washington. Mt. Baker and Snoqualmie Pass can expect around an inch of water equivalent Thursday night. Snow levels should rise above Snoqualmie pass level at some point Thursday night, drastically limiting snow totals, but above the rain/snow line, significant snow accumulations are expected. W winds should continue to increase into the moderate to strong range, particularly for areas favored by strong downslope acceleration.

On Friday, the perturbation moves east. Rain and snow should decrease in the light to moderate range. Snow levels remain near or just above Snoqualmie Pass level. Downslope winds are likely to peak early Friday in the strong to very strong range.