January 17, 2017

MOUNTAIN WEATHER FORECAST

Time and Day: 0700 Tuesday

The Snapshot:  Let the games begin. 360 on the upper mountain and 160 in the base area with overcast skies.  A complicated storm with several embedded fronts will begin to affect the PNW today.   

The Science:  The first batch of precipitation leading the charge is currently entering the western slopes of the Cascades.  Freezing levels over Western Washington are 7-9000’ with cold easterly flow mixing at the Passes.  This means the moisture is starting out as rain and freezing as it falls into the cold air and onto frozen surfaces.   Yuk. 

The leading edge of the stronger warm front is still offshore and is expected to make landfall later today. Once this front enters the mountains, the freezing levels over Stevens Pass will bump up to +-6000’ and the precipitation (rain) will increase.  Moderate to heavy rain is expected after 4 pm today with the rain shifting to intermittent showers tomorrow.   Cool unstable flow fills in on Thursday with snow showers persisting for the remainder of the week.  

The Long Range:   Active, snowy weather continues through the weekend as a low-pressure trough moves into place.   

Precipitation Ending at 4 am:

Today 24hr water = 1-1.5  Snow = 1-4

Tomorrow’s 24hr water = .75  snow = 1-3

Trend and Timing:
Mixed rain and snow and freezing rain changing to rain tonight, rain showers tomorrow.


24hr temperature ending at 4 am tomorrow: 
Low:  30   High: 40
Freezing level: +-5000’

Trend and Timing:   
Freezing levels will rise today and peak around 6000’ tomorrow.
 
24hr Winds (mph) ending at 4 am tomorrow:
Base:  0-5 E
Ridge Top: 5-10 SSW

Trend and Timing:
 Southerly flow aloft with east flow at the surface will change westerly over the next 24-36hrs.




jM

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0800 start for Tuesday 12/23/25, no ABS

 Setup Crew