Mountain Weather Forecast

Weather Synopsis

Moisture continues to stream into the area as an atmospheric river impacts the region through Monday night. Freezing levels in most areas west of the Cascade Crest rose to 5000-6500 ft Monday afternoon. Expect these warm temperatures to persist through Monday even, but begin lowering as the front approaches in the early morning hours. Heavy rain and high-elevation snow focus on the volcanoes, particularly Mt Baker. Although precipitation was slow to pick up for Mt Baker on Christmas day, we expect upwards of 2" of snow water equivalent in 12 hours with snow levels dropping from 5000 to 4000 ft overnight. The flow pattern has not favored the major passes, but as the front arrives late Monday night, expect the possibility of a period of heavier precipitation and a potential shift from mixed precipitation to rain at Snoqualmie Pass as E flow relaxes somewhat heading into Tuesday morning. Snow or wintry mix remains most likely for Stevens Pass where 3-4" of snow accumulation is possible.

Precipitation rapidly decreases behind the front early Tuesday, but a convergence band likely maintains some locally moderate precipitation rates in the Mt Baker vicinity through mid-morning. By the afternoon, expect snow levels across the west slopes of the Cascades to lower to around 3500 ft with mostly cloudy skies and sprinkles/flurries.

Easterly flow rapidly intensifies as another deep offshore low spins off the coast. Expect moderate to locally strong E winds through the mountain gaps Tuesday night with a slightly weaker cold pool than with the last system along the east slopes of the Cascades.

A front splits somewhat and loses energy as it moves into the region on Wednesday afternoon. Expect bands of light precipitation to arrive on SSW flow during the day and focus on the volcanoes and S slopes of the Olympics. Strong E flow peaks during the morning hours and may bring another round of mixed precipitation to the passes.