Mountain Weather Forecast

Time and Day: 0830 Saturday

The Snapshot:  One more dry and cold day with increasing clouds Saturday. Light snow tonight, moderate snow and warmer temperatures Sunday.

The Science: A bitterly cold morning at Stevens Pass with all weather stations showing low single digit temps. The persistent upper level NE flow and dry, cold weather should begin to change today as a low pressure system retrogrades (moves west) off the coast of BC and sets up several hundred miles offshore. This should change the upper level flow pattern affecting the Pacific Northwest to southwesterly, allowing warm and moist Pacific air to impact the region. A weak warm front should reach Stevens Pass late Saturday, bringing light snow. A second, stronger warm front should impact the forecast area midday Sunday. East flow in the passes should maintain locally colder temperatures before the cold air gets scoured out late Sunday night.

The dramatic difference between the large pool of cold air currently in place, and the overriding warm moisture that will move into Western Washington should provide a mix of precipitation types on Sunday. Freezing rain is possible in the passes, with outright rain unlikely and snow at the beginning and end of the day Sunday.

Freezing rain is likely in the Puget Sound on Sunday, likely impacting driving conditions.

The Long Range: After the warm front passes, the low pressure cell will move onshore and open into a trough bringing continued light snow showers at low freezing levels Monday and Tuesday. Low amplitude high and low pressure systems alternate the rest of the week for light-moderate snow events through Friday.

Precipitation Ending at 4am: Today 24hr water = >.25  Snow = 1-3” Tomorrow’s 24hr water = .5-.75  Snow = 4-8” Trend and Timing: Light snow beginning late Saturday evening, becoming moderate with the possibility of mixed precip Sunday midday. A final shot of moderate snow should fall Sunday night and Monday morning.

24hr temperature ending at 4 am tomorrow:                                        Low:  4   High: 20 Freezing level: 0’-500’ Trend and Timing:    Surface temperatures should remain cold at Stevens Pass thru Sunday morning, with free air freezing levels rising rapidly during the day Sunday.

24hr Winds (mph) ending at 4 am tomorrow: Base: E 5-15 Ridge Top: E 20-30 Trend and Timing: East winds should remain in place through Sunday midday, before switching to westerly. DV