MOUNTAIN WEATHER FORECAST

Stevens Pass Mountain Weather Forecast

Day and Time: 007 Thursday

Current Observations:

24hr Precipitation:  2” of pow

Temperature profile: 32base, 28 ridge

Pass level winds: light westerlies

Barometer: 1025mbs and rising

Sky: Fog in the base with broken clouds above

Radar: Snow flurries in Walla Walla. 

The Forecast:  Early morning fog burning off through the day with warming temperatures are on the docket for today.  Warmer temperatures with clearing begins tomorrow and last through the weekend. 

Long Range:  The weekend will be mostly clear with daytime temperatures reaching into the 40s’.  Models have this dry and unseasonably warm weather persisting through most of next week.     

  

The Science:  High pressure will begin to dominate the weather pattern for the next 5-7 days.   A warm stable air mass will slide over Western Washington pushing freezing levels above 10,000’ over the next 36-48hrs. 

The general flow will shift northerly then NE on Sunday and Monday for some cold early morning temperatures likely. 

Values from 4am today through

 4am tomorrow.

Precipitation: Today 24hr water: 0  snow: 0 Tomorrow’s 24hr water: 0  snow: 0 Trend and Timing: 0

Temperature: Low:  28   High: 34 Freezing level: > 4500’ Trend and Timing:    Freezing levels will slowly rise over the next 24 hour possibly peaking +- 8000’ on Saturday.

Winds Base: 0-5 W Ridge Top:  5-10 WNW Trend and Timing: Light westerly flow will shift NW over the next 24hrs.

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…

The Inter-mountain West….. the region between the Rock Mountains 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.

High/Low Pressure…. High pressure is associated with sinking air that rotates clockwise. High pressure often results in dry and clear weather.  Low pressure is rising air that rotates counter clockwise and results in condensation, cloud formation and precipitation.

Atmospheric Stability….. A stable atmosphere is associate with high pressure or the inability for air to rise.  Instability or an unstable atmosphere forms under low pressure or rising air.