MOUNTAIN WEATHER FORECAST

Time and Day:  0900 Saturday

The Snapshot: Light mixed precip this afternoon and evening, moderate to occasionally heavy snow Sunday afternoon/evening.

Current Observations:  Partly cloudy skies and light east winds at Stevens Pass this morning, 30 degrees in the base area and 27 up top. There was a very light trace of new snow yesterday, RH values are in the 90’s and the barometer has been steady for the past 12 hours.

The Science: Clouds in advance of the next weather system to affect Washington are spreading east this morning. A low pressure system off the coast will deepen today, allowing upper level flow from the south to bring a warm front, and then the trailing cold front, across the region. Free air freezing levels will rise during the day Saturday but precipitation shouldn’t begin until the afternoon. Precip may start as light rain or freezing rain at Stevens Pass, but with cool air in place to the east and light east winds indicated thru the night, snow isn’t out of the question either. Either way, precip amounts look pretty light by mid-morning Sunday.

The trailing cold front will swing thru mid day Sunday, bringing a dramatic drop in freezing levels and increase in westerly winds. Precip may start out as rain but should quickly changeover to snow Sunday afternoon. Moderate snow looks to continue into Monday, with a few heavy showers indicated and potential convergence centered over Stevens Pass during the day Monday.

The Long Range:  The trough passes Monday, with zonal flow during the day bringing continued snow showers. Another trough approaches and crosses the area Tuesday, bringing moderate to heavy snow to Stevens Pass. 72 hour snow amounts ending Wednesday afternoon look to be around 18+”. Upper level ridging begins Wednesday with Thursday and Friday looking dry before yet another system approaches Friday afternoon.

24hr Precipitation ending at 4am: Today 24hr water: >.25  snow:0-2” Tomorrow’s 24hr water: .75  snow: 6+” Trend and Timing: Light precip beginning late Saturday afternoon, ending briefly Sunday morning before becoming moderate to heavy Sunday night and Monday.

24hr temperature ending at 4am:  Low: 27    High: 36 Free Air Freezing level: 3500-6500’ Trend and Timing:    Freezing level will rise dramatically during the day Saturday and thru Sunday morning; however, east flow could limit local snow levels to Pass level Sunday morning.

24hr Winds (mph) ending at 4am: Base: E 5-10, Ridge Top: SSE 10-20 Trend and Timing: Easterly flow looks to hang in there thru Sunday morning, before switching to gusty and westerly in the base area and on ridge tops. DV