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Mountain Weather Forecast

Issued: 7:43 AM PST Wednesday, February 7, 2018
by Robert Hahn

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 Wednesday & Thursday

On Wednesday, the Pacific Northwest continues to sit between a robust and relatively stationary high pressure off the northern coast of California and a deep low over Hudson's Bay. The jetstream lies to our north, taking today's storm track and precipitation on a higher-latitude trajectory than previously expected. The result will be even warmer than anticipated for Wednesday, with relatively drier weather and lower wind speeds.

The atmosphere this morning is very stable on Wednesday morning, meaning that the temperature doesn't decrease significantly with height as you normally expect. Temperatures are in the low-to-mid 30's at most NWAC stations, including Camp Muir!

What little precipitation does fall today will be mostly very light rain or high elevation snow above treeline in the north or central Cascades. 

Conditions today will feature moderate to strong westerly flow in the alpine with light to moderate winds at pass level.

Tonight, W-SW winds will increase to the moderate-to-strong range by morning at crest level and snow levels will begin lowing slightly as the jetstream drops southward, pushing the ridge back south.

A reasonably strong, but relatively moisture-starved surface cold front associated with a short-wave trough will cross the Pacific Northwest on Thursday, arriving in the Olympics and NW Cascades around 10 AM and reaching Mt. Hood during the evening hours.

Snow levels will drop significantly behind the front with rain changing back to snow at many mid-elevation locations between 4 and 7 PM, with a changeover at Snoqualmie Pass likely after 7 PM. Most precipitation will be with light post-frontal showers behind the cold front, with light snowfall accumulation from Snoqualmie Pass northward Thursday afternoon and evening. Thursday

Weather forecast for Wednesday & Thursday

Olympics
Date Weather
Wednesday Partly cloudy with filtered sunlight. Moderate ridgetop westerly winds.
Wednesday Night Fair with partly cloudy skies. Moderate ridgetop W-SW winds increasing to strong at times.
Thursday Mostly cloudy, becoming partly cloudy in the afternoon. Strong ridgetop W-SW winds.
Becoming mostly clear. Moderate ridgetop westerly winds.
Washington Cascades near and west of the Crest including Stevens, Snoqualmie and White Passes
Date Weather
Wednesday Decreasing generally very light rain or snow early, central and north part. Filtered sunlight south Cascades in the morning becoming filtered sunlight in the afternoon in the central Cascades with partly cloudy skies to the north. Moderate crest-level westerly winds.
Wednesday Night Mostly high clouds. Crest-level winds becoming moderate to strong.
Thursday Mostly cloudy in the morning from Snoqualmie Pass northward, becoming partly cloudy in the afternoon. Expect filtered sunlight further south in the morning with low clouds moving in during the afternoon. Moderate to strong W-SW crest-level winds.
Mostly cloudy with westerly winds decreasing.
East Slopes of the Washington Cascades
Date Weather
Wednesday Decreasing generally very light rain or snow early, central and north part. Filtered sunlight south Cascades in the morning becoming filtered sunlight in the afternoon in the central Cascades with partly cloudy skies to the north. Moderate crest-level westerly winds.
Wednesday Night Mostly high clouds. Crest-level winds becoming moderate to strong.
Thursday Mostly cloudy in the morning from Snoqualmie Pass northward, becoming partly cloudy in the afternoon. Expect filtered sunlight further south. Moderate to strong W-SW crest-level winds.
Becoming partly to mostly clear with westerly winds decreasing.
Mt. Hood
Date Weather
Wednesday Low clouds dissipating early, then increasing high clouds.
Wednesday Night High clouds.
Thursday Increasing clouds in the afternoon.
Mostly cloudy.

Snow Level/Freezing Level in feet

Date Olympics Northwest Cascades Northeast Cascades Central Cascades South Cascades Easterly Flow in Passes
Wednesday Morning Snow Level 8000' 4500' 5500' 7000' 9500'
Wednesday Afternoon Snow Level 8000' 5500' 6000' 7500' 9000'
Wednesday Night Snow Level 6500' 5000' 5500' 6500' 9000'
Thursday Morning Snow Level 5000' 4000' 4000' 4000' 8000'
Thursday Afternoon Snow Level 4000' 4000' 4500' 4000' 8500'
Olympics
Date Elevation
Wednesday Morning Snow Level
8000'
Wednesday Afternoon Snow Level
8000'
Wednesday Night Snow Level
6500'
Thursday Morning Snow Level
5000'
Thursday Afternoon Snow Level
4000'
Thursday Night Snow Level
2500'
Northwest Cascades
Date Elevation
Wednesday Morning Snow Level
4500'
Wednesday Afternoon Snow Level
5500'
Wednesday Night Snow Level
5000'
Thursday Morning Snow Level
4000'
Thursday Afternoon Snow Level
4000'
Thursday Night Snow Level
2500'
Northeast Cascades
Date Elevation
Wednesday Morning Snow Level
5500'
Wednesday Afternoon Snow Level
6000'
Wednesday Night Snow Level
5500'
Thursday Morning Snow Level
4000'
Thursday Afternoon Snow Level
4500'
Thursday Night Snow Level
3000'
Central Cascades
Date Elevation
Wednesday Morning Snow Level
7000'
Wednesday Afternoon Snow Level
7500'
Wednesday Night Snow Level
6500'
Thursday Morning Snow Level
4000'
Thursday Afternoon Snow Level
4000'
Thursday Night Snow Level
3000'
South Cascades
Date Elevation
Wednesday Morning Snow Level
9500'
Wednesday Afternoon Snow Level
9000'
Wednesday Night Snow Level
9000'
Thursday Morning Snow Level
8000'
Thursday Afternoon Snow Level
8500'
Thursday Night Snow 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 Thu Fri
Hurricane Ridge 0 0
Mt Baker Ski Area lt .25 .25 - .50
Washington Pass 0 .25
Stevens Pass lt .10 .50
Snoqualmie Pass lt .10 .25 - .50
Mission Ridge 0 0
Crystal Mt 0 0
Paradise 0 lt .10
White Pass 0 lt .10
Mt Hood Meadows 0 0

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

Date Direction - Speed
Wednesday Morning W 10 - 20
Wednesday Afternoon W 10 - 20
Wednesday Night W 20 - 30
Thursday Morning W 20 - 30
Thursday Afternoon W 15 - 25

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
Wednesday Morning W 20 - 30 WSW 15 - 25 W 15 - 25 W 10 - 20
Wednesday Afternoon W 20 - 30 W 15 - 25 W 10 - 20 W 10 - 20
Wednesday Night WSW 25 - 40 WSW 20 - 35 WSW 30 - 40 WSW 30 - 40
Thursday Morning WSW 25 - 35 WSW 20 - 30 WSW 30 - 40 WSW 30 - 40
Thursday Afternoon WSW 20 - 30 WSW 10 - 20 WSW 25 - 35 W 30 - 40
Olympics
Date Elevation
Wednesday Morning W 20 - 30
Wednesday Afternoon W 20 - 30
Wednesday Night WSW 25 - 40
Thursday Morning WSW 25 - 35
Thursday Afternoon WSW 20 - 30
Thursday Night WSW 5 - 15
Northwest Cascades
Date Elevation
Wednesday Morning WSW 15 - 25
Wednesday Afternoon W 15 - 25
Wednesday Night WSW 20 - 35
Thursday Morning WSW 20 - 30
Thursday Afternoon WSW 10 - 20
Thursday Night SW 5 - 15
Central Cascades
Date Elevation
Wednesday Morning W 15 - 25
Wednesday Afternoon W 10 - 20
Wednesday Night WSW 30 - 40
Thursday Morning WSW 30 - 40
Thursday Afternoon WSW 25 - 35
Thursday Night W 5 - 15
South Cascades
Date Elevation
Wednesday Morning W 10 - 20
Wednesday Afternoon W 10 - 20
Wednesday Night WSW 30 - 40
Thursday Morning WSW 30 - 40
Thursday Afternoon W 30 - 40
Thursday Night W 20 - 35
Olympics
Date Direction - Speed
Wednesday Morning W 20 - 30
Wednesday Afternoon W 20 - 30
Wednesday Night WSW 25 - 40
Thursday Morning WSW 25 - 35
Thursday Afternoon WSW 20 - 30
Thursday Night WSW 5 - 15
Northwest Cascades
Date Direction - Speed
Wednesday Morning WSW 15 - 25
Wednesday Afternoon W 15 - 25
Wednesday Night WSW 20 - 35
Thursday Morning WSW 20 - 30
Thursday Afternoon WSW 10 - 20
Thursday Night SW 5 - 15
Central Cascades
Date Direction - Speed
Wednesday Morning W 15 - 25
Wednesday Afternoon W 10 - 20
Wednesday Night WSW 30 - 40
Thursday Morning WSW 30 - 40
Thursday Afternoon WSW 25 - 35
Thursday Night W 5 - 15
South Cascades
Date Direction - Speed
Wednesday Morning W 10 - 20
Wednesday Afternoon W 10 - 20
Wednesday Night WSW 30 - 40
Thursday Morning WSW 30 - 40
Thursday Afternoon W 30 - 40
Thursday Night W 20 - 35

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
Wednesday Morning WNW 40 - 60 W 45 - 65 WNW 45 - 65 NW 30 - 40
Wednesday Afternoon W 45 - 65 W 50 - 70 W 50 - 70 WNW 25 - 35
Wednesday Night WSW 50 - 70 WSW 60 - 80 WSW 60 - 80 W 50 - 70
Thursday Morning WSW 35 - 45 WSW 50 - 70 W 40 - 60 W 60 - 80
Thursday Afternoon W 25 - 35 WSW 30 - 40 W 40 - 60 W 55 - 75
Northwest Cascades
Date Direction - Speed
Wednesday Morning WNW 40 - 60
Wednesday Afternoon W 45 - 65
Wednesday Night WSW 50 - 70
Thursday Morning WSW 35 - 45
Thursday Afternoon W 25 - 35
Thursday Night W 10 - 20
Northeast Cascades
Date Direction - Speed
Wednesday Morning W 45 - 65
Wednesday Afternoon W 50 - 70
Wednesday Night WSW 60 - 80
Thursday Morning WSW 50 - 70
Thursday Afternoon WSW 30 - 40
Thursday Night W 15 - 25
Central Cascades
Date Direction - Speed
Wednesday Morning WNW 45 - 65
Wednesday Afternoon W 50 - 70
Wednesday Night WSW 60 - 80
Thursday Morning W 40 - 60
Thursday Afternoon W 40 - 60
Thursday Night WNW 35 - 55
South Cascades
Date Direction - Speed
Wednesday Morning NW 30 - 40
Wednesday Afternoon WNW 25 - 35
Wednesday Night W 50 - 70
Thursday Morning W 60 - 80
Thursday Afternoon W 55 - 75
Thursday Night NW 45 - 65

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.