MOUNTAIN WEATHER FORECAST

Stevens Pass Mountain Weather Forecast

Day and Time:   Saturday 1030

Current Observations:

24hr Precipitation:  1.04swe. 6-8” of snow

Temperature profile: 33 base,  28 ridge

Pass level winds: Light W

Barometer: 1015mb’s rising

Sky: OC

Radar: light scattered showers along the western slopes of the mountains.

The Forecast: Drying, cooling and partial clearing develops today and continues through Monday. 

Long Range:  Snow with rising freezing levels can be anticipated on Tuesday/ Wednesday with the remainder of the week trending dry and clear.  

  

The Science: A dirty ridge of high pressure sliding over the Cascade Mountains today will begin to stabilize and dry atmosphere.   Cooler air aloft will allow freezing levels to drop to +-3000’ tonight.  Some clearing will also help cool surface temperatures during the early morning hours.

The next weather system to keep eye on will arrive on Tuesday.  There are significant discrepancies with the details, so for now expect snow and the possibility of some mixed rain on Tuesday and Wednesday.

Values from 4am today through

 4am tomorrow.

Precipitation: Today 24hr water: .24  snow: 1-3 Tomorrow’s 24hr water: 0  snow: 0 Trend and Timing: Snow showers will diminish today with tomorrow being mostly dry.

Temperature: Low: 24    High: 34 Freezing level: 4500’ – 3500’ Trend and Timing:    Freezing levels will slowly fall today to +-3000’.

Winds Base:0-5 W Ridge Top: 5-10 W Trend and Timing: Pass level winds will be light with gusty ridgetop winds possible through the day.

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…

Inter Mountain West…. The region between the Rocky Mountain and the Cascade Mountain ranges.   Mainly Idaho and Western Montana

Puget Sound Convergence Zone…. This is formed when large scale westerly flow splits around the Olympic Mountains and then converges over Puget Sound.  The flow then accelerates up the river valley’s enhancing the orographic effect at the Passes.

Occluded Front….The boundary that separates the cold air mass behind a cold front and the warm air associated with a warm front.  When the cold front overtakes the warm front it occludes.