MOUNTAIN WEATHER FORECAST

Stevens Pass Mountain Weather Forecast

Wednesday, 12/31/19, 0730

Current Observations:

24hr Precipitation:      .15 SWE, 1” of snow

Temperature profile:    31 base, 30 ridge

Pass level winds:            light, westerly

Barometer:                   1014mb’s  and falling

Sky:                              OC and snowing

Radar:           Heavy moisture entering Puget Sound and tracking E

The Forecast:  Heavy rain today then turning back to snow tomorrow.  Winds will also crank up this afternoon with ridge top gust +40pmh possible.  Heavy mixed rain and snow turning to snow can be anticipated tomorrow.

Long Range. A similar event is taking shape for the start of the New Year.  Snow on Thursday changing to rain Friday back to snow Saturday.     

  

The Science:  A strong warm front with a long fetch of moisture will drive into the PNW today.  Warm air advection has begun to stream in in from the SW with the leading edge of the approaching warm front entering Puget Sound.  Freezing levels top out above 6000’ this afternoon and then slowly fall through the night. 

The big question is when the rain will turn back to snow and how much snow accumulation we will get tomorrow.  Snow totals tomorrow could exceed 15”.  There will likely be convergence zone activity with and trough wave tomorrow which will aid in orographic snowfall at Stevens Pass. 

There will be a short break Thursday morning with the next system entering the scene Thursday afternoon.   Freezing levels once again rise to +5000’ on Friday with moderate to heavy rain likely.   

Long range models have a strong cold front with cool unstable NW flow arriving over the weekend with measurable snow heading into the first full week of 2020.

Confidence:  Fair

Values from 4am today through 4am tomorrow.

Precipitation: Today 24hr water: 1-2 snow: 1-3    Tomorrow’s 24hr water: 1.5   snow:  10-15 Trend and Timing: Heavy rain today.  Rain switches back to snow tomorrow with good accumulation likely.

Temperature: Low: 31  High: 38 Freezing level: 4000’ – 6000’ – 4500’ Trend and Timing:    Freezing levels will peak around 6000’ this afternoon and then fall through the night.

Winds Base: 5-15 W Ridge Top:  10-20 W with gust +40 Trend and Timing: A high wind warning will go into affect this afternoon with sustained 40+mph winds at and above 5000’.