MOUNTAIN WEATHER FORECAST

Stevens Pass Mountain Weather Forecast

Monday, December 16, 2019, 0900

Current Observations:

24hr Precipitation:        0

Temperature profile:      23 base,  22 ridge

Pass level winds:              light, westerly

Barometer:                    1022mb’s and holding

Sky:                                  broken mid-level clouds

Radar:       There is precipitation falling west of Seattle with an approaching warm front making landfall.

The Forecast:  Light snow showers today with rising temperatures.  Mostly dry tomorrow with increasing clouds.  

Long Range:  Snow returns on Wednesday with heavy snow Thursday afternoon/evening.   Warming with a possible rain event late Thursday night into Friday morning. The weekend is trending dry with clearing.

Early storm total estimates from Wednesday 4am - through Friday 4am =1.5-2”SWE,  12-15”snow.  There is a warm component that comes into play late Thursday night into Friday morning that we will need to keep an eye on. 

  

The Science: The high pressure ridge over the PNW will slowly degrade today.   This will open the door for the approaching warm front to drift NE. Most of the associated moist will be north of Stevens Pass

Southerly flow aloft will bring warm air advection up the west and east slopes of the Cascades today.  This will push freezing levels up to Pass level; weak east flow will hopefully hold temperatures at or just below freezing.  

The developing low pressure system in the Gulf of Alaska will bring the next system of interest to the PNW Wednesday morning.   Strong, moist westerly flow with favorable freezing levels will start the show with snow ramping up on Thursday.   The trough deepens late Thursday night into Friday which may shift the flow southerly and warmer.  We will have watch the freezing levels closely as a moderate to heavy rain event may be possible.  

Confidence: Goods short-term,  fair long range.

Values from 4am today through 4am tomorrow.

Precipitation: Today 24hr water: lt.10 snow: trace Tomorrow’s 24hr water: lt.10   snow: 0 Trend and Timing: Flurries today with mostly dry conditions expected through tomorrow.

Temperature: Low:  22  High: 30 Freezing level: 1500’ – 4000’ Trend and Timing:   Freezing levels will begin to rise today.  East flow will help aid in holding temperature at or below the freezing mark.

Winds Base: 0-5 W shifting E Ridge Top: 0-10 W shifting SSE Trend and Timing: Pass level east flow will develop tonight with southerly flow above 5000’.