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Mountain Weather Forecast

Issued: 8:08 AM PST Saturday, April 29, 2017
by Kenny Kramer

The NWAC program is administered by the USDA-Forest Service and operates from the National Weather Service Forecast Office in Seattle. NWAC services are made possible by important collaboration and support from a wide variety of federal, state and private cooperators.

NWAC Spring Forecast Schedule

The NWAC issued daily mountain weather and avalanche forecasts through Saturday, April 15th. Mountain weather and avalanche forecasts will be issued during the spring transition April 20-22nd and April 27-29th. Weekend outlooks will be issued Thursdays, May 4th, 11th, 18th and 25th.

Weather synopsis for Saturday & Sunday

An upper level ridge of high pressure is weakening along the coast early Saturday as a cold front approaches from the west. A deck of high clouds has spread rapidly across the Olympics and NW Washington early Saturday and will cover the remainder of the forecast area through the day Saturday. The front should bring light precipitation initially to the Olympics and NW Washington Cascades Saturday afternoon.

The main frontal passage should move across the Cascade crest before midnight, and pass the Mt Hood area early Sunday morning.  A period of moderate precipitation should accompany the frontal passage with showers following by early Sunday. Freezing levels rise modestly overnight and cool behind the front by early Sunday.

Onshore flow should maintain showers, mainly along the west slope Cascade areas early Sunday and diminish or end during the day Sunday.

Upper level high pressure begins to rebuild along the coast Sunday night to allow for a cool but drying NW flow aloft. 

Weather forecast for Saturday & Sunday

Olympics
Date Weather
Saturday Morning

Increasing high clouds becoming mostly cloudy.

Saturday Afternoon - Saturday Night

Light rain and snow developing Saturday afternoon. Light to briefly moderate rain and snow Saturday night, changing to showers late.

Sunday

Partly to mostly cloudy with light rain and snow showers. Showers diminishing or ending afternoon.

Diminishing clouds becoming partly to mostly clear.

Washington Cascades near and west of the crest including Stevens, Snoqualmie, and White Passes
Date Weather
Saturday

Increasing high clouds early. Clouds lowering in the north with a chance of light rain or snow Saturday afternoon.

Saturday Afternoon - Saturday Night

Light rain and snow developing in the north Saturday afternoon and in the central and south by evening or early Saturday night. Light to briefly moderate rain and snow Saturday night. Rain and snow changing to showers late night.

Sunday

Partly to mostly cloudy with light rain and snow showers. Showers diminishing or ending afternoon.

Diminishing clouds becoming partly cloudy.

East slopes of the Washington Cascades
Date Weather
Saturday

Increasing high clouds.

Saturday Night

Periods of light rain and snow, changing to light showers late night.

Sunday

Partly to mostly cloudy with light rain and snow showers at times, mainly nearer the crest. Showers diminishing or ending afternoon.

Becoming mostly clear.

Mt. Hood Area
Date Weather
Saturday

Clear early with increasing high clouds.

Saturday Night

Light rain and snow developing Saturday evening. Light to briefly moderate rain and snow Saturday night.

Sunday

Mostly cloudy with light rain and snow showers early. Showers diminishing or ending afternoon.

Becoming partly to mostly clear.

Snow Level/Freezing Level in feet

Date Olympics Northwest Cascades Northeast Cascades Central Cascades South Cascades Easterly Flow in Passes
Saturday Morning Freezing Level 5500' 5500' 5500' 5500' 6000'
Saturday Afternoon - Night Snow Level 5500' 5000' 5000' 5500' 6500'
Sunday Morning Snow Level 3000' 3500' 3500' 3500' 4500'
Sunday Afternoon Snow Level 3500' 4000' 4000' 4000' 4500'
Olympics
Date Elevation
Saturday Morning Freezing Level
5500'
Saturday Afternoon - Night Snow Level
5500'
Sunday Morning Snow Level
3000'
Sunday Afternoon Snow Level
3500'
Sunday Night Freezing Level
4000'
Northwest Cascades
Date Elevation
Saturday Morning Freezing Level
5500'
Saturday Afternoon - Night Snow Level
5000'
Sunday Morning Snow Level
3500'
Sunday Afternoon Snow Level
4000'
Sunday Night Freezing Level
4500'
Northeast Cascades
Date Elevation
Saturday Morning Freezing Level
5500'
Saturday Afternoon - Night Snow Level
5000'
Sunday Morning Snow Level
3500'
Sunday Afternoon Snow Level
4000'
Sunday Night Freezing Level
4500'
Central Cascades
Date Elevation
Saturday Morning Freezing Level
5500'
Saturday Afternoon - Night Snow Level
5500'
Sunday Morning Snow Level
3500'
Sunday Afternoon Snow Level
4000'
Sunday Night Freezing Level
4500'
South Cascades
Date Elevation
Saturday Morning Freezing Level
6000'
Saturday Afternoon - Night Snow Level
6500'
Sunday Morning Snow Level
4500'
Sunday Afternoon Snow Level
4500'
Sunday Night Freezing Level
4500'

Cascade Snow / Freezing Levels noted above refer to the north (approximately Mt Baker and Washington Pass), central (approximately Stevens to White Pass) and south (near Mt Hood). Freezing Level is when no precipitation is forecast.
* Note that surface snow levels are common near the passes during easterly pass flow and may result in multiple snow / freezing levels.

24 Hour Quantitative Precipitation ending at 4 am

Location Sun Mon
Hurricane Ridge .25 lt .10
Mt Baker Ski Area .50 lt .25
Washington Pass lt .25 lt .10
Stevens Pass .25 lt .25
Snoqualmie Pass .25 - .50 lt .25
Mission Ridge 0 lt .10
Crystal Mt lt .25 lt .10
Paradise .25 - .50 lt .25
White Pass lt .25 lt .10
Mt Hood Meadows .25 lt .25

Winds in Miles per Hour (MPH) "Cascade Pass Level Winds"

Date Direction - Speed
Saturday - Saturday Night W 0 - 10
Sunday Morning W 5 - 15

Directions above indicate the direction the wind blows from on the 16-point cardinal scale. Winds near the passes tend to be highly channeled by the topography and normally blow either easterly or westerly depending on the surface pressure gradients that drive such winds.

Free Winds at 5000' (in Miles per Hour (MPH))

Date Olympics Northwest Cascades Central Cascades South Cascades
Saturday Morning SW 0 - 10 SW 0 - 10 SW 0 - 10 WSW 0 - 10
Saturday Afternoon SSW 20 - 30 SSW 15 - 25 SW 10 - 20 WSW 10 - 20
Saturday Night SW 15 - 25 SW 15 - 25 SW 25 - 35 SW 25 - 35
Olympics
Date Elevation
Saturday Morning SW 0 - 10
Saturday Afternoon SSW 20 - 30
Saturday Night SW 15 - 25
Sunday - Sunday Night W 10 - 20
Northwest Cascades
Date Elevation
Saturday Morning SW 0 - 10
Saturday Afternoon SSW 15 - 25
Saturday Night SW 15 - 25
Sunday - Sunday Night W 10 - 20
Central Cascades
Date Elevation
Saturday Morning SW 0 - 10
Saturday Afternoon SW 10 - 20
Saturday Night SW 25 - 35
Sunday - Sunday Night W 15 - 25
South Cascades
Date Elevation
Saturday Morning WSW 0 - 10
Saturday Afternoon WSW 10 - 20
Saturday Night SW 25 - 35
Sunday - Sunday Night W 15 - 25
Olympics
Date Direction - Speed
Saturday Morning SW 0 - 10
Saturday Afternoon SSW 20 - 30
Saturday Night SW 15 - 25
Sunday - Sunday Night W 10 - 20
Northwest Cascades
Date Direction - Speed
Saturday Morning SW 0 - 10
Saturday Afternoon SSW 15 - 25
Saturday Night SW 15 - 25
Sunday - Sunday Night W 10 - 20
Central Cascades
Date Direction - Speed
Saturday Morning SW 0 - 10
Saturday Afternoon SW 10 - 20
Saturday Night SW 25 - 35
Sunday - Sunday Night W 15 - 25
South Cascades
Date Direction - Speed
Saturday Morning WSW 0 - 10
Saturday Afternoon WSW 10 - 20
Saturday Night SW 25 - 35
Sunday - Sunday Night W 15 - 25

Directions above indicate the direction the wind blows from on the 16-point cardinal scale. These winds and the 9000 ft winds below also indicate "free" winds, or those winds in the atmosphere not influenced by terrain. Topographical effects may produce greater or lower wind speeds in certain locations as well as significant variations in direction.

Free Winds at 9000' (in Miles per Hour (MPH))

Date Northwest Cascades Northeast Cascades Central Cascades South Cascades
Saturday Morning W 15 - 25 W 5 - 15 W 10 - 20 W 10 - 20
Saturday Afternoon - Saturday Night WSW 30 - 40 WSW 30 - 40 WSW 30 - 40 WSW 30 - 40
Sunday WNW 15 - 25 WNW 20 - 30 WNW 25 - 35 WNW 30 - 40
Northwest Cascades
Date Direction - Speed
Saturday Morning W 15 - 25
Saturday Afternoon - Saturday Night WSW 30 - 40
Sunday WNW 15 - 25
Sunday Night NW 5 - 15
Northeast Cascades
Date Direction - Speed
Saturday Morning W 5 - 15
Saturday Afternoon - Saturday Night WSW 30 - 40
Sunday WNW 20 - 30
Sunday Night NW 5 - 15
Central Cascades
Date Direction - Speed
Saturday Morning W 10 - 20
Saturday Afternoon - Saturday Night WSW 30 - 40
Sunday WNW 25 - 35
Sunday Night NW 15 - 25
South Cascades
Date Direction - Speed
Saturday Morning W 10 - 20
Saturday Afternoon - Saturday Night WSW 30 - 40
Sunday WNW 30 - 40
Sunday Night NW 15 - 25

Directions above indicate the direction the wind blows from on the 16-point cardinal scale. These winds indicate "free" winds, or those winds in the atmosphere not influenced by terrain. Topographical effects may produce greater or lower wind speeds in certain locations as well as significant variations in direction.

The Extended Mountain Weather Forecast (Days 3-5) will be included with the afternoon forecast issuance around 1:30 PM.