MOUNTAIN WEATHER FORECAST

Stevens Pass Mountain Weather Forecast

Wednesday, December 11, 2019, 0900a

Current Observations:

24hr Precipitation:        .13 SWE, 1” of snow

Temperature profile:      32 base, 29 ridge

Pass level winds:             light, westerly

Barometer:                    1014mb’s and slowly falling

Sky:                     base area fog with broken mid-level clouds

Radar:                light spotty snow showers to the NW of Stevens with rain south of Olympia. The next band of moisture is just making land fall.

The Forecast:  Light mixed rain and snow showers this morning with heavier moisture arriving late this afternoon.  Tomorrow will be sporty with gusty winds and moderate to heavy precipitation.  

Long Range:  The snow machine will continue into Friday morning with the weekend trending dry.     

Storm totals from 4am today through 4pm Friday = +-2”SWE, 15-20” snow.

  

The Science:  A triple point storm will spin its way toward the PNW today.  Upper level air models suggest that the freezing levels will be in favor of snow for Stevens Pass.  It will be possible to see a bit or rain mixed in from time to time, but the majority of the moisture will hopefully be white.

With all triple points, the leading warm front will swing through first, quickly follow by the cold front.  Once the cold front passes late tonight or early tomorrow morning, the westerly flow will strengthen.  The Puget Sound Convergence will play a role in determining snow amounts tomorrow.  Wind will also be a factor tomorrow afternoon and evening as pressure gradients tighten.     

Confidence:  Fair

Values from 4am today through 4am tomorrow.

Precipitation: Today 24hr water: .5+  snow:  3-5” - +-6 possible on upper mountain   Tomorrow’s 24hr water: .75-1  snow: 7-10” Trend and Timing: The moisture will ramp up this afternoon and continue through tomorrow.

Temperature: Low: 30   High:  34 Freezing level: +4000’ -4500’ Trend and Timing:    Freezing levels will hover near 4000’ or slightly higher through tomorrow.  East flow with cooler upper air will help snow levels be at or just below Pass level.

Winds Base:  0-5 E shifting W and strengthening Ridge Top:  5-10 ESE shifting W tomorrow morning Trend and Timing: Pass level east flow will persist through the night. Winds will quickly shift westerly during the early morning hours and strengthen.  +30mph ridge top winds will be likely tomorrow afternoon.