Mountain Weather Forecast

Weather Synopsis

A stalled front over Washington State has created a tremendous snowfall event that has been most significant where firmly entrenched cold air along the east slopes of the Cascades combines with upslope low-level easterly flow on Friday. The stalled front has been usurped by recently formed low offshore. This low tracks toward southern Washington and should arrive Monday morning. As it approaches, the warm frontal boundary lifts further north, allowing the very heavy rain and snow to expand northward into the North Cascades including the Mt. Baker area, which was mostly dry on Thursday. The moisture feed should decrease very slowly as the approaching trough brings cooling aloft, so while precipitation rates in most areas should back off very gradually, but remain intense. Low-level easterly flow also gradually decreases, so allowing more warm air to work its way to mid-elevations east of the Cascade Crest, potentially creating a setup for freezing rain in cooler valley locations. Winds should also increase across the region as the system approaches with widespread strong ridgeline winds possible through Friday morning.

The low moves in with a sharp temperate front and westerly wind shift, so by late morning on Friday, expect more showery and lighter precipitation. The exception will be in convergence bands likely focused on the Stevens Pass area, where high rates of snowfall are expected into the afternoon as temperatures cool rapidly. The westerly wind shift will also bring another round of moderate to strong winds to the east slopes of the Cascades in the afternoon, notably the Washington Pass area.

WNW flow continues with decreasing snow shower activity and weaker convergence possible Friday night which will become very light and relegated to the west slopes of the Cascades by Saturday. Temperatures should be cold with snow levels dropping below Snoqualmie Pass level by Saturday morning.