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Mountain Weather Forecast

Issued: 2:08 PM PST Thursday, April 27, 2017
by Garth Ferber

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 Thursday & Friday

An  upper shortwave will move northwest to southeast over the Northwest on Thursday with a W-NW 150 knot jet directed to western Oregon. Minor instability to about 10,000 feet and minor convergence zone effects to the central Washington Cascades should be seen the remainder of Thursday afternoon. But some more snow will be seen at Mt Hood on Thursday afternoon where there is more flow aloft and more moisture.

An upper ridge and a drier air mass will shift east over the US coastal waters to the west US on Friday. Surface high pressure will shift to over the Northwest. Northwest flow aloft will decrease with fair weather by Friday afternoon and a modest rise in freezing levels.

Weather forecast for Thursday & Friday

Olympics
Date Weather
Thursday Afternoon

Partly cloudy.

Thursday Night - Friday Morning

Clearing.

Friday Afternoon

Mostly sunny.

Partly or mostly clear in the evening. Increasing high clouds after midnight.

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

Light snow showers.

Thursday Night - Friday Morning

Light snow showers ending.

Friday Afternoon

Partly or mostly sunny.

Partly or mostly clear.

East slopes of the Washington Cascades
Date Weather
Thursday Afternoon

Light snow showers higher elevations.

Thursday Night - Friday Morning

Light snow showers higher elevations ending.

Friday Afternoon

Mostly sunny.

Mostly clear.

Mt. Hood Area
Date Weather
Thursday Afternoon

Light to moderate snow showers heaviest west side.

Thursday Night - Friday Morning

Light snow showers mainly west side ending.

Friday Afternoon

Partly sunny west side and mostly sunny east side.

Partly or mostly clear.

Snow Level/Freezing Level in feet

Date Olympics Northwest Cascades Northeast Cascades Central Cascades South Cascades Easterly Flow in Passes
Thursday Afternoon Snow Level 4000' 4000' 4000' 4000' 4000'
Thursday Night - Friday Morning Snow Level 3000' 2500' 3000' 2500' 2500'
Friday Afternoon Freezing Level 5500' 5500' 6000' 5500' 5500'
Olympics
Date Elevation
Thursday Afternoon Snow Level
4000'
Thursday Night - Friday Morning Snow Level
3000'
Friday Afternoon Freezing Level
5500'
Friday Night Freezing Level
4500'
Northwest Cascades
Date Elevation
Thursday Afternoon Snow Level
4000'
Thursday Night - Friday Morning Snow Level
2500'
Friday Afternoon Freezing Level
5500'
Friday Night Freezing Level
4000'
Northeast Cascades
Date Elevation
Thursday Afternoon Snow Level
4000'
Thursday Night - Friday Morning Snow Level
3000'
Friday Afternoon Freezing Level
6000'
Friday Night Freezing Level
4000'
Central Cascades
Date Elevation
Thursday Afternoon Snow Level
4000'
Thursday Night - Friday Morning Snow Level
2500'
Friday Afternoon Freezing Level
5500'
Friday Night Freezing Level
4500'
South Cascades
Date Elevation
Thursday Afternoon Snow Level
4000'
Thursday Night - Friday Morning Snow Level
2500'
Friday Afternoon Freezing Level
5500'
Friday Night Freezing Level
5500'

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 Fri Sat
Hurricane Ridge lt .10 0
Mt Baker Ski Area .25 lt .10
Washington Pass lt .10 lt .10
Stevens Pass .25 lt .10
Snoqualmie Pass .25 lt .10
Mission Ridge 0 0
Crystal Mt .25 0
Paradise .25 0
White Pass .25 0
Mt Hood Meadows .50 - .75 0

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

Date Direction - Speed
Thursday Afternoon - Thursday Evening W 15 - 25
Thursday Night - Friday W 10 - 20

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
Thursday Afternoon WNW 20 - 30 WNW 10 - 20 WNW 15 - 25 WNW 25 - 35
Thursday Night - Friday Morning WNW 10 - 20 WNW 5 - 15 WNW 10 - 20 WNW 20 - 30
Friday Afternoon WNW 5 - 15 WNW 5 - 15 WNW 5 - 15 WNW 10 - 20
Olympics
Date Elevation
Thursday Afternoon WNW 20 - 30
Thursday Night - Friday Morning WNW 10 - 20
Friday Afternoon WNW 5 - 15
Friday Night VAR 0 - 10
Northwest Cascades
Date Elevation
Thursday Afternoon WNW 10 - 20
Thursday Night - Friday Morning WNW 5 - 15
Friday Afternoon WNW 5 - 15
Friday Night VAR 0 - 10
Central Cascades
Date Elevation
Thursday Afternoon WNW 15 - 25
Thursday Night - Friday Morning WNW 10 - 20
Friday Afternoon WNW 5 - 15
Friday Night VAR 0 - 10
South Cascades
Date Elevation
Thursday Afternoon WNW 25 - 35
Thursday Night - Friday Morning WNW 20 - 30
Friday Afternoon WNW 10 - 20
Friday Night VAR 0 - 10
Olympics
Date Direction - Speed
Thursday Afternoon WNW 20 - 30
Thursday Night - Friday Morning WNW 10 - 20
Friday Afternoon WNW 5 - 15
Friday Night VAR 0 - 10
Northwest Cascades
Date Direction - Speed
Thursday Afternoon WNW 10 - 20
Thursday Night - Friday Morning WNW 5 - 15
Friday Afternoon WNW 5 - 15
Friday Night VAR 0 - 10
Central Cascades
Date Direction - Speed
Thursday Afternoon WNW 15 - 25
Thursday Night - Friday Morning WNW 10 - 20
Friday Afternoon WNW 5 - 15
Friday Night VAR 0 - 10
South Cascades
Date Direction - Speed
Thursday Afternoon WNW 25 - 35
Thursday Night - Friday Morning WNW 20 - 30
Friday Afternoon WNW 10 - 20
Friday Night VAR 0 - 10

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
Thursday Afternoon WNW 10 - 20 WNW 10 - 20 WNW 25 - 35 WNW 30 - 45
Thursday Night - Friday Morning WNW 10 - 20 WNW 15 - 25 WNW 15 - 25 WNW 20 - 30
Friday Afternoon WNW 10 - 20 WNW 5 - 15 WNW 15 - 25 WNW 10 - 20
Northwest Cascades
Date Direction - Speed
Thursday Afternoon WNW 10 - 20
Thursday Night - Friday Morning WNW 10 - 20
Friday Afternoon WNW 10 - 20
Friday Night W 15 - 25
Northeast Cascades
Date Direction - Speed
Thursday Afternoon WNW 10 - 20
Thursday Night - Friday Morning WNW 15 - 25
Friday Afternoon WNW 5 - 15
Friday Night W 5 - 15
Central Cascades
Date Direction - Speed
Thursday Afternoon WNW 25 - 35
Thursday Night - Friday Morning WNW 15 - 25
Friday Afternoon WNW 15 - 25
Friday Night W 10 - 20
South Cascades
Date Direction - Speed
Thursday Afternoon WNW 30 - 45
Thursday Night - Friday Morning WNW 20 - 30
Friday Afternoon WNW 10 - 20
Friday Night W 15 - 25

Extended Weather Synopsis for Saturday through Monday

A weakening front will move over the ridge and over the Northwest Saturday night. Despite moving over a ridge the Thursday morning UW WRF run shows just as much precipitation in the south Cascades as the north Cascades.

Another weaker front should move over the ridge and over the Northwest on Monday. This system should affect the Olympics and north to central Cascades more than the south Cascades.

Extended Weather Forecast for Saturday through Monday

Olympics, Washington Cascades, Mt Hood
Date Weather
Saturday

Increasing mid and high clouds initially in the Olympics and north Cascades.

Saturday Night - Sunday

Light to moderate rain or snow Saturday night mainly Olympics, west slopes of the Washington Cascades ant Mt Hood. Light rain or snow showers Sunday mainly Olympics, west slopes of the Washington Cascades ant Mt Hood.

Snow/Freezing Levels

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

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.