MOUNTAIN WEATHER FORECAST

Stevens Pass Mountain Weather Forecast

Day and Time:  Wednesday Jan 16^th, 0630a

Current Observations:

24hr Precipitation: 0

Temperature profile: 20 base, 17 ridges

Pass level winds: moderate gusts ENE

Barometer: holding at 1009mb’s

Sky: partly cloudy skies over Stevens Pass with high clouds to the west. The inversion layer is still intact over the eastern basin.

Radar: some precipitation echoes are starting to pop up just off the Washington coast  

The Forecast: There will be one more day of dry, cool weather with snow arriving early tomorrow morning.  Snow increases tomorrow night with a potential powder day shaping up for Friday. 

Long Range:  More precipitation with rising freezing levels (+4500”) is expected on Saturday, cooler with snow can be anticipated for Sunday / Monday.   

  

The Science:  The high pressure over the Intermountain West that brought us this mini ice age, is beginning to weaken and drift east.  A large low pressure system with several imbedded frontal systems will bring an active storm track back to the PNW starting tomorrow.   

The game will start out tomorrow morning with light snow out ahead of the main cold front.  Friday morning, the east flow will give way to strong WSW flow. This will provide a period of good orographic snowfall.   Warm air advection, driven by strong SW flow arrives on Saturday. We will have to watch the freezing levels with this system as they rise to or above 4500’.    

Confidence is good through Friday morning and fair for the warmup on Saturday.   

Values from 4am today through

 4am tomorrow.

Precipitation: Today 24hr water: .10  snow: 1-2 Tomorrow’s 24hr water: .75   snow: 6-8 Trend and Timing: Light snow arrives after 2am tomorrow morning with heavier snow developing tomorrow night.

Temperature: Low: 20    High: 26 Freezing level: 2000’ – 3000’ Trend and Timing:    Freezing levels will remain below 3000’ over the next 24hrs with the aid of east flow.

Winds Base: 5-15 E gusty Ridge Top: 10-15 E Trend and Timing: Easterly winds will increase today and remain intact through early Friday morning.

Glossary of PNW Weather Terms: 

Storm Water Equivalent (SWE)…. how much water is in the snow or rain

Orographic lift…. an airmass that is lifted as it moves up and over higher terrain. This promotes cloud development, and enhances precipitation.

Dirty Ridge…. a weak, unorganized high pressure ridge.

Advection…. the transfer of heat by the flow of fluid.  For the PNW, this is usually from warm moist air entering the region from the south.

Flow…. wind direction.  In meteorology, the wind direction is always noted where the wind is coming from.   East flow is wind coming from the east; SW is from the south west…

Intermountain West…. the mountain ranges between the Rockies and the Cascades.  Mainly Idaho and Western Montana.