MOUNTAIN WEATHER FORECAST

Stevens Pass Mountain Weather Forecast

Wednesday, December 18, 2019, 0730.

Current Observations:

24hr Precipitation:      0

Temperature profile:    20 base,  18 ridge

Pass level winds:          light to moderate, easterly

Barometer:                 1011mbs and dropping

Sky:                             Overcast

Radar:   The leading edge of the incoming moisture, ahead of the cold front, is still a few miles offshore and tracking ENE.

The Forecast:  Mostly dry today with snow arriving after 4pm.  The snow will diminish tomorrow with moderate to heavy precipitation returning late tomorrow afternoon.  There is a chance of rain early Friday morning with cooling through the day.

  

Long Range:  Snow showers persist from Friday afternoon through Saturday with Sunday and Monday trending dry.  

  

The Science:  The cool east flow is winning out with the temperature inversion now overcome.  The moisture out ahead of the approaching cold front is expected to enter the mountains late this afternoon with temperatures remaining well below freezing.  

As the trough deepens tomorrow, the flow will shift SSW with warm air driving in.   Satellite images show heavy moisture be entrained in this SW flow feature.  Freezing level are expected to rise above 5000’ early Friday morning with moderate to heavy rain likely.  Uncertainty lies with when the freezing levels fall back below 4000’ on Friday. 

The atmosphere will remain unstable with cooling temperatures through Saturday. With some luck we will pick up another +-6” of snow by the time is all comes to and end Saturday night.  

Confidence: Fair

Values from 4am today through 4am tomorrow.

Precipitation: Today 24hr water: .25-.5 snow: 3-5 Tomorrow’s 24hr water: 1  snow: 5-10 (possibility of rain) Trend and Timing: Snow will begin after 4pm and fall through the night. Light snow showers will diminish tomorrow with the next wave of heavy moisture expected to hit the mountain after 4pm tomorrow afternoon.

Temperature: Low: 22   High:  26 Freezing level: +-3000’ Trend and Timing:    Freezing levels will hold around 3000’ with the aid of east flow.  Temperature begin to rise tomorrow afternoon.

Winds Base: 5-10 E Ridge Top: 5-10 ESE Trend and Timing: East flow should hold through the night. Winds shift westerly and increase in the wake of the cold front sometime tomorrow morning.