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Mountain Weather Forecast

Issued: 7:46 AM PST Thursday, February 8, 2018
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.

Weather synopsis for Thursday & Friday

The PNW lies between a large upper ridge extending to the Gulf of Alaska and a broad trough over western Canada. This is maintaining strong WNW flow aloft over the forecast area early Thursday.

A weak disturbance is approaching the area from the north in this strong WNW flow. Not a great deal of moisture is associated with the front but it will cause a period of light to moderate precipitation as it passes. Little moisture will make it south of about Mt Rainier Thursday.

The greatest expected precipitation will be over the Stevens to Snoqualmie Pass area in an active convergence zone which should persist through Thursday night. The convergence has already formed early Thursday and is directed over the Stevens Pass area. Outside of the convergence zone areas of Stevens and Snoqualmie Passes, only very light amounts of precipitation are expected Thursday.

Freezing levels remain relatively high early Thursday but should lower significantly in the wake of the passing disturbance Thursday evening and overnight.

The ridge offshore gains strength Friday and turns the upper level flow to a more northerly direction. This should cause further cooling but more drying with only a few scattered showers expected Friday.

Weather forecast for Thursday & Friday

Olympics
Date Weather
Thursday Mostly cloudy, becoming partly cloudy in the afternoon. Strong ridgetop W winds.
Thursday Night Becoming mostly clear. Moderate ridgetop W winds.
Friday Partly cloudy and cool.
Mostly clear. Cool.
Washington Cascades near and west of the Crest including Stevens, Snoqualmie and White Passes
Date Weather
Thursday Increasing light or moderate rain and snow showers with lowering snow levels in the afternoon. Heaviest rain or snow in convergence near Stevens Pass to Snoqualmie Pass in the afternoon. Cloudy with light rain or snow in the southern part from about Mt Rainier southward. Moderate to strong W-SW crest-level winds.
Thursday Night Showers diminishing in the passes. Otherwise, mostly cloudy, with westerly winds decreasing.
Friday Partly cloudy and cool.
Mostly clear and cool.
East Slopes of the Washington Cascades
Date Weather
Thursday Mostly cloudy with light rain or snow, mainly nearer the crest. Filtered sunshine away from the crest. Cooling late.
Thursday Night Partly cloudy and cool.
Friday Mostly sunny and cool.
Mostly clear and cool.
Mt. Hood
Date Weather
Thursday Mostly fair in the morning with increasing clouds in the afternoon.
Thursday Night Mostly cloudy. Gradual cooling
Friday Mostly sunny and cool.
Clear and cool.

Snow Level/Freezing Level in feet

Date Olympics Northwest Cascades Northeast Cascades Central Cascades South Cascades Easterly Flow in Passes
Thursday Morning Snow Level 6500' 4500' 4500' 6000' 7500'
Thursday Afternoon Snow Level 3500' 3500' 3500' 4000' 7500'
Thursday Night Snow Level 2500' 2000' 2000' 2500' 6000'
Friday Morning Snow Level 2000' 1500' 1500' 2000' 3000'
Friday Afternoon Snow Level 2000' 1500' 1500' 2000' 3000'
Olympics
Date Elevation
Thursday Morning Snow Level
6500'
Thursday Afternoon Snow Level
3500'
Thursday Night Snow Level
2500'
Friday Morning Snow Level
2000'
Friday Afternoon Snow Level
2000'
Friday Night Snow Level
1500'
Northwest Cascades
Date Elevation
Thursday Morning Snow Level
4500'
Thursday Afternoon Snow Level
3500'
Thursday Night Snow Level
2000'
Friday Morning Snow Level
1500'
Friday Afternoon Snow Level
1500'
Friday Night Snow Level
500'
Northeast Cascades
Date Elevation
Thursday Morning Snow Level
4500'
Thursday Afternoon Snow Level
3500'
Thursday Night Snow Level
2000'
Friday Morning Snow Level
1500'
Friday Afternoon Snow Level
1500'
Friday Night Snow Level
500'
Central Cascades
Date Elevation
Thursday Morning Snow Level
6000'
Thursday Afternoon Snow Level
4000'
Thursday Night Snow Level
2500'
Friday Morning Snow Level
2000'
Friday Afternoon Snow Level
2000'
Friday Night Snow Level
2000'
South Cascades
Date Elevation
Thursday Morning Snow Level
7500'
Thursday Afternoon Snow Level
7500'
Thursday Night Snow Level
6000'
Friday Morning Snow Level
3000'
Friday Afternoon Snow Level
3000'
Friday Night Snow Level
2000'

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 - .50 lt .10
Washington Pass .25 lt .10
Stevens Pass .75 lt .10
Snoqualmie Pass .50 lt .10
Mission Ridge 0 0
Crystal Mt lt .10 0
Paradise lt .25 lt .10
White Pass lt .10 lt .10
Mt Hood Meadows 0 0

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

Date Direction - Speed
Thursday Morning W 10 - 20
Thursday Afternoon W 15 - 25
Thursday Night W 10 - 20
Friday Morning W 5 - 15
Friday Afternoon 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
Thursday Morning W 25 - 35 WSW 15 - 25 W 30 - 40 W 20 - 30
Thursday Afternoon W 15 - 25 W 15 - 25 W 20 - 30 WNW 15 - 25
Thursday Night WNW 10 - 20 WNW 10 - 20 WNW 15 - 25 WNW 15 - 25
Friday Morning N 5 - 10 NNE 5 - 10 NW 10 - 20 NW 5 - 15
Friday Afternoon N 5 - 10 NE 5 - 15 NW 5 - 15 NW 5 - 15
Olympics
Date Elevation
Thursday Morning W 25 - 35
Thursday Afternoon W 15 - 25
Thursday Night WNW 10 - 20
Friday Morning N 5 - 10
Friday Afternoon N 5 - 10
Friday Night NE 10 - 20
Northwest Cascades
Date Elevation
Thursday Morning WSW 15 - 25
Thursday Afternoon W 15 - 25
Thursday Night WNW 10 - 20
Friday Morning NNE 5 - 10
Friday Afternoon NE 5 - 15
Friday Night NE 10 - 20
Central Cascades
Date Elevation
Thursday Morning W 30 - 40
Thursday Afternoon W 20 - 30
Thursday Night WNW 15 - 25
Friday Morning NW 10 - 20
Friday Afternoon NW 5 - 15
Friday Night NE 5 - 15
South Cascades
Date Elevation
Thursday Morning W 20 - 30
Thursday Afternoon WNW 15 - 25
Thursday Night WNW 15 - 25
Friday Morning NW 5 - 15
Friday Afternoon NW 5 - 15
Friday Night NE 5 - 15
Olympics
Date Direction - Speed
Thursday Morning W 25 - 35
Thursday Afternoon W 15 - 25
Thursday Night WNW 10 - 20
Friday Morning N 5 - 10
Friday Afternoon N 5 - 10
Friday Night NE 10 - 20
Northwest Cascades
Date Direction - Speed
Thursday Morning WSW 15 - 25
Thursday Afternoon W 15 - 25
Thursday Night WNW 10 - 20
Friday Morning NNE 5 - 10
Friday Afternoon NE 5 - 15
Friday Night NE 10 - 20
Central Cascades
Date Direction - Speed
Thursday Morning W 30 - 40
Thursday Afternoon W 20 - 30
Thursday Night WNW 15 - 25
Friday Morning NW 10 - 20
Friday Afternoon NW 5 - 15
Friday Night NE 5 - 15
South Cascades
Date Direction - Speed
Thursday Morning W 20 - 30
Thursday Afternoon WNW 15 - 25
Thursday Night WNW 15 - 25
Friday Morning NW 5 - 15
Friday Afternoon NW 5 - 15
Friday Night NE 5 - 15

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 Morning W 40 - 60 W 45 - 65 W 45 - 65 WNW 40 - 60
Thursday Afternoon WNW 30 - 40 WNW 35 - 50 WNW 40 - 60 WNW 40 - 60
Thursday Night WNW 15 - 25 WNW 30 - 40 WNW 35 - 50 WNW 40 - 60
Friday Morning NW 15 - 25 NW 15 - 25 NW 30 - 40 NW 30 - 40
Friday Afternoon NNW 15 - 25 NNW 20 - 30 NW 15 - 25 NW 30 - 40
Northwest Cascades
Date Direction - Speed
Thursday Morning W 40 - 60
Thursday Afternoon WNW 30 - 40
Thursday Night WNW 15 - 25
Friday Morning NW 15 - 25
Friday Afternoon NNW 15 - 25
Friday Night NNE 10 - 20
Northeast Cascades
Date Direction - Speed
Thursday Morning W 45 - 65
Thursday Afternoon WNW 35 - 50
Thursday Night WNW 30 - 40
Friday Morning NW 15 - 25
Friday Afternoon NNW 20 - 30
Friday Night NNE 10 - 20
Central Cascades
Date Direction - Speed
Thursday Morning W 45 - 65
Thursday Afternoon WNW 40 - 60
Thursday Night WNW 35 - 50
Friday Morning NW 30 - 40
Friday Afternoon NW 15 - 25
Friday Night N 10 - 20
South Cascades
Date Direction - Speed
Thursday Morning WNW 40 - 60
Thursday Afternoon WNW 40 - 60
Thursday Night WNW 40 - 60
Friday Morning NW 30 - 40
Friday Afternoon NW 30 - 40
Friday Night NNW 10 - 20

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 between 2 - 3 PM.