MOUNTAIN WEATHER FORECAST

Stevens Pass Mountain Weather Forecast

Tuesday, December 10, 2019, 0700a

Current Observations:

24hr Precipitation:         0

Temperature profile:      26 base,  33ridge

Pass level winds:              light, easterly

Barometer:                       1018mb’s and falling

Sky:                                   high  clouds

Radar:    dry throughout the state with the incoming moisture just about to make land fall along the SW coast of Washington.

The Forecast: Increasing clouds this morning with light mixed rain and snow starting this afternoon.   Light snow showers persist through the night with moderate moisture arriving tomorrow afternoon.  Temperatures will be near freezing through the end of the week.  

Long Range: A progressive wet weather pattern will develop with moderate to heavy precipitation expected for the next 5+ days.  How much snow you ask?   The freezing levels will be on the cusp of the Stevens Pass rain/snow line so it is unclear at this point. The upper mountain should get some decent snow.

Storm totals from 4pm today through 4am Saturday = +2” SWE with 8-15” of snow likely at or above 4500’.   

  

The Science: The large low pressure system that has developed in the Gulf of Alaska will drive a series of storms into the PNW over the next week or so.  The first wave, out ahead of a cold front, will arrive this afternoon.  Freezing levels will be +-4500’ tonight with mixed forms.  Once the cold front pushes through tonight, temperature will fall a few degrees with light snow showers expected. 

The next wetter system arrives tomorrow afternoon/evening with strong westerly flow filling in behind.  Thursday will be sporty with high winds and moderate to heavy precipitation likely.  The snow/rain line is the big question through Friday with cooler air expected by the weekend.      

Forecast confidence: Fair due to the freezing level questions.

Values from 4am today through 4am tomorrow.

Precipitation: Today 24hr water: .25  snow: 1-2 Tomorrow’s 24hr water: .75  snow: 1-3 base, 3-6 upper ridge Trend and Timing: We should begin to see the moisture falling around 2pm today.  The precipitation will ramp up again tomorrow afternoon.

Temperature: Low: 26   High:  34 Freezing level: +- 4500’ Trend and Timing:    Freezing levels will stabilize around 4500’ with little fluctuation in temperatures through the night.

Winds Base: 0-5 E shifting W Ridge Top: 5-10 W Trend and Timing: East flow at the surface with WSW 5000’ winds are expected today. Surface flow will shift westerly tonight with the passing of the front.

jM