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Mountain Weather Forecast

Issued: 3:09 PM 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

Strong WNW flow near and above crest level persists across the Pacific Northwest Thursday afternoon. The region is being squeezed between an upper ridge offshore and a trough across western Canada, thus tightening the gradients over the forecast area.

A  weak frontal boundary moved across the region early Thursday causing a period of mostly light precipitation at high freezing levels. Low level moisture is now being lifted along the west slopes in moderate onshore flow, maintaining light precipitation along the west slopes and over the volcanoes.

Little moisture will make it much further south than about Mt Rainier Thursday afternoon and night.

The greatest expected precipitation will be over the Stevens to Snoqualmie Pass area in an active convergence zone which should gradually weaken Thursday night. 

Freezing levels remain relatively high Thursday afternoon and 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 Afternoon 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 Afternoon Periods of light or moderate rain and snow showers with slowly lowering snow levels. Heaviest rain or snow in convergence near Stevens Pass to Snoqualmie Pass. Cloudy with occasional light rain or snow in the southern part south of about Mt Rainier. 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 Afternoon Mostly cloudy with light rain or snow showers, mainly nearer the crest. Filtered sunshine away from the crest.
Thursday Night Partly cloudy and cool.
Friday Mostly sunny and cool.
Mostly clear and cool.
Mt. Hood
Date Weather
Thursday Afternoon Increasing clouds.
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 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 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 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 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 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 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 .50 lt .10
Washington Pass .25 0
Stevens Pass .75 lt .10
Snoqualmie Pass .50 lt .10
Mission Ridge 0 0
Crystal Mt lt .10 0
Paradise .25 - .50 lt .10
White Pass lt .10 0
Mt Hood Meadows lt .10 0

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

Date Direction - Speed
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 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 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 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 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 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 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 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 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 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 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 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 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 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 Afternoon WNW 40 - 60
Thursday Night WNW 40 - 60
Friday Morning NW 30 - 40
Friday Afternoon NW 30 - 40
Friday Night NNW 10 - 20

Extended Weather Synopsis for Saturday through Monday

The region should be dominated by cool and dry northerly flow aloft on Saturday, being on the downwind side of the upper ridge offshore. This should provide a mostly fair and cool day Saturday.

There remains a great deal of uncertainty in the computer weather models regarding an expected disturbance to impact the region Sunday. One strong case tracks the system from off Vancouver Island early Sunday southward, mostly offshore, providing only a glancing blow. Another solution is to move the disturbance across the region. Either way, it is not a strong system, but the details remain uncertain. Whatever precipitation received should fall with relatively low freezing levels.

The ridge offshore should rebound Monday to bring a cool and drier NNE flow. Showers should end early Monday with gradual clearing.

 

Extended Weather Forecast for Saturday through Monday

Olympics, Washington Cascades and Mt. Hood Area
Date Weather
Saturday A mostly sunny day and clear night Saturday and Saturday night. Cool.
Sunday Cloudy with periods of light to briefly moderate snow beginning in the north part early Sunday and tracking southward through the day. Track of disturbance remains uncertain.

Snow/Freezing Levels

Date Olympics Northwest Cascades Northeast Cascades Central Cascades South Cascades Easterly Flow in Passes
Saturday Freezing Level 2500' - 4500' 1500' - 3500' 1500' - 3500' 3000' - 5000' 3000' - 5000'
Saturday Night Freezing Level 2500' - 4000' 1500' - 2500' 1500' - 2500' 3500' - 5000' 4500' - 6000'
Sunday Snow Level 1000' - 2500' 500' - 1500' 0' - 1000' 1000' - 2500' 3000' - 4000'
Sunday Night Snow Level 1500' - 2500' 500' - 1500' 500' - 1500' 1500' - 2500' 2000' - 3000'
Olympics
Date Elevation
Saturday Freezing Level
2500' - 4500'
Saturday Night Freezing Level
2500' - 4000'
Sunday Snow Level
1000' - 2500'
Sunday Night Snow Level
1500' - 2500'
Monday Snow Level
2000' - 3500'
Northwest Cascades
Date Elevation
Saturday Freezing Level
1500' - 3500'
Saturday Night Freezing Level
1500' - 2500'
Sunday Snow Level
500' - 1500'
Sunday Night Snow Level
500' - 1500'
Monday Snow Level
2000' - 3500'
Northeast Cascades
Date Elevation
Saturday Freezing Level
1500' - 3500'
Saturday Night Freezing Level
1500' - 2500'
Sunday Snow Level
0' - 1000'
Sunday Night Snow Level
500' - 1500'
Monday Snow Level
1500' - 3000'
Central Cascades
Date Elevation
Saturday Freezing Level
3000' - 5000'
Saturday Night Freezing Level
3500' - 5000'
Sunday Snow Level
1000' - 2500'
Sunday Night Snow Level
1500' - 2500'
Monday Snow Level
2000' - 3000'
South Cascades
Date Elevation
Saturday Freezing Level
3000' - 5000'
Saturday Night Freezing Level
4500' - 6000'
Sunday Snow Level
3000' - 4000'
Sunday Night Snow Level
2000' - 3000'
Monday Snow Level
2000' - 3000'

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.