MOUNTAIN WEATHER FORECAST

Stevens Pass Mountain Weather Forecast

Date: Sunday, December 29, 2019

Current Observations:

24hr Precipitation: 0”

Temperature profile: 23 base / 31 mid mtn

Pass level winds:  Light easterly

Barometer:  Steady at 1016

Sky:  Foggy / overcast

Radar:  Light showers across the Olympic Peninsula and South Sound

The Forecast: Foggy and cold with inversion conditions in base area, partly cloudy and warmer mid and upper mountain.

The Science: A slow moving, weak low pressure system off the Washington coast is pushing up against higher pressure inland this morning and spreading light rain to the Olympic Peninsula. Little more than high clouds will reach the Central Cascades. The pressure gradient is driving east flow thru the mountain passes, creating surface inversions and locally cold temperatures and fog. As the low pressure sinks south and dissipates, a positively tilted high pressure ridge will lean over the PNW for Monday, bringing another dry day and mild temperatures aloft.

Long Range: A significant pattern shift is in store starting New Year’s Eve as a strong jet begins to drive several storms into our region. Freezing levels start near/above Pass level but lower throughout the second half of the week. Details to come.

Confidence:

Values from 4am today through 4am tomorrow.

Precipitation: Today 24hr water: 0 snow: 0 Tomorrow’s 24hr water: <.10  snow: trace Trend and Timing: Dry today and daylight hours Monday, chance of light snow early Tuesday morning.

Temperature: Low: 23   High: 35 Freezing level: 5,000’ / surface at Pass level Trend and Timing:    Free air freezing levels will rise today, east flow will keep inversion conditions and below freezing temperatures on the lower half of the mountain.

Winds Base: E 5-15 Ridge Top: E 5-10 Trend and Timing: East flow thru the Pass will continue thru Monday morning.