MOUNTAIN WEATHER FORECAST

Stevens Pass Mountain Weather Forecast

Day and Time: Friday 0700

Current Observations:

24hr Precipitation: 0

Temperature profile: 31base, 26 ridge

Pass level winds: light westerly

Barometer:1025mb’s and on the rise 

Sky: mostly clear

Radar:  

The Forecast: While the Upper Midwest goes into the deep freeze with -25f to -35 degrees below zero forecasted, the west coast could see record high temperatures.  Temperatures could hit 50^0f during the peak of the day tomorrow.  

Long Range:  This stretch of dry weather will continue through most of next week. Cooler air from the east will move in on Sunday and Monday for some freezing temperatures.

  

The Science: A high amplitude ridge, currently parked off of the PNW waters, will ease its way inland over next 24hrs.  The main feature of interest is the unseasonably warm air mass associated with this high pressure system.  Freezing levels over Westerly Washington could peak above 10,000’ with Pass temperatures hitting 40’s or even 50 degrees tomorrow.

Cooler offshore (east) flow will bring temperatures back to normal on Sunday with a melt freeze cycle developing early of next week.   

Values from 4am today through

 4am tomorrow.

Precipitation: Today 24hr water: 0  snow: 0 Tomorrow’s 24hr water: 0  snow: 0 Trend and Timing: Dry weather will persist.

Temperature: Low: 30    High: 40 Freezing level: + 6000’ Trend and Timing:    Temperature will continue to climb today with freezing levels topping 8000’ tomorrow.

Winds Base: 0-10 NW Ridge Top: 5-15 NW Trend and Timing: Pass level winds will be light with gusty ridge top winds possible.

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.