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Mountain Weather Forecast

Issued: 2:58 PM PST Thursday, March 8, 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 Thursday & Friday

An open trough and weakening surface low sit just W-SW of Cape Flattery on Thursday afternoon. The low will dissipate as it crosses the Olympics, but the associated upper trough will continue to bring moderate rain and snow to the mountains.

Moderate free air winds (and stronger gusts) will be out of the south today, switching to SW after 4PM when the occluded front associated with the dying low crosses the Cascades, then westerly as a secondary upper trough and stronger surface cold front swings through from the NW around 1 AM. Temperatures will drop sharply behind the cold front and most locations will change back to snow as precipitation intensities are decreasing.

Easterly flow is keeping the passes cool so far on Thursday afternoon. However, Snoqualmie should see a changeover to rain around 4PM with the passage of the occluded front with a changeover back to Snow between 1 and 4 AM on Friday. Stevens Pass may see a changeover to rain during the evening hours before changing back to snow after midnight. Mt. Baker base is now back to snow and should remain wet snow until the cold front cools things the atmosphere further.

On Thursday night, precipitation should decrease behind the cold front. In the early morning hours, a convergence zone is likely to develop in the Stevens Pass vicinity and could push as far south as Snoqualmie. Snow shower activity will be light Friday and will taper off. Temperatures will be cool.

On Friday night, skies will becoming mostly clear as high pressure builds over the region.

 

Weather forecast for Thursday & Friday

Olympics
Date Weather
Thursday Periods of light rain and snow.
Thursday Night Light rain and snow changing to all snow after midnight. Moderate SW winds changing to westerly winds after midnight.
Friday Cold in the morning with snow showers ending early; otherwise partly cloudy.
Mostly clear.
Washington Cascades near and west of the Crest including Stevens, Snoqualmie and White Passes
Date Weather
Thursday Moderate rain and snow. Moderate easterly winds in the passes. Moderate (gusting to strong) southerly winds.
Thursday Night Moderate rain and snow in the evening, changing to light to moderate snow showers after midnight, heaviest in convergence near Stevens Pass. Moderate SW winds switching to westerly after midnight.
Friday Light snow showers, decreasing. Otherwise mostly cloudy skies.
Partly cloudy with ESE winds developing after midnight.
East Slopes of the Washington Cascades
Date Weather
Thursday Light to moderate rain and snow. Moderate easterly winds in the passes. Moderate (gusting to strong) southerly winds.
Thursday Night Light to moderate rain and snow in the evening, changing to light snow showers after midnight, heaviest in convergence near Stevens Pass. Moderate SW winds switching to westerly after midnight.
Friday Light snow showers near the Cascade Crest, decreasing. Otherwise partly sunny skies.
Mostly clear.
Mt. Hood
Date Weather
Thursday Moderate rain and snow. Strong S-SW winds.
Thursday Night Moderate rain and snow along with strong SW winds becoming light snow showers in the early morning hours with moderate to strong W-SW winds.
Friday Rapidly decreasing light snow showers in the morning and partly cloudy skies in the afternoon. Decreasing moderate westerly winds.
Clear skies with rising freezing levels and light winds.

Snow Level/Freezing Level in feet

Date Olympics Northwest Cascades Northeast Cascades Central Cascades South Cascades Easterly Flow in Passes
Thursday Afternoon Snow Level 4500' 3500' 3000' 3500' 4500' *
Thursday Night Snow Level 2000' 2000' 2500' 3000' 3500'
Friday Morning Snow Level 2000' 1500' 1500' 1500' 1500'
Friday Afternoon Snow Level 2500' 2000' 2000' 3000' 3500'
Olympics
Date Elevation
Thursday Afternoon Snow Level
4500'
Easterly Flow*
Thursday Night Snow Level
2000'
Friday Morning Snow Level
2000'
Friday Afternoon Snow Level
2500'
Friday Night Freezing Level
2000'
Northwest Cascades
Date Elevation
Thursday Afternoon Snow Level
3500'
Easterly Flow*
Thursday Night Snow Level
2000'
Friday Morning Snow Level
1500'
Friday Afternoon Snow Level
2000'
Friday Night Freezing Level
2000'
Northeast Cascades
Date Elevation
Thursday Afternoon Snow Level
3000'
Easterly Flow*
Thursday Night Snow Level
2500'
Friday Morning Snow Level
1500'
Friday Afternoon Snow Level
2000'
Friday Night Freezing Level
1500'
Central Cascades
Date Elevation
Thursday Afternoon Snow Level
3500'
Easterly Flow*
Thursday Night Snow Level
3000'
Friday Morning Snow Level
1500'
Friday Afternoon Snow Level
3000'
Friday Night Freezing Level
2000'
South Cascades
Date Elevation
Thursday Afternoon Snow Level
4500'
Easterly Flow*
Thursday Night Snow Level
3500'
Friday Morning Snow Level
1500'
Friday Afternoon Snow Level
3500'
Friday Night Freezing Level
3000'

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 .50 - .75 lt .10
Mt Baker Ski Area 1.50 - 2.00 lt .10
Washington Pass 1.00 lt .10
Stevens Pass 1.00 .25
Snoqualmie Pass 1.50 lt .25
Mission Ridge .25 lt .10
Crystal Mt .75 - 1.00 lt .10
Paradise 1.00 - 1.50 lt .10
White Pass .75 - 1.00 lt .10
Mt Hood Meadows .75 - 1.00 lt .10

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

Date Direction - Speed
Thursday Afternoon E 20 - 30
Thursday Night W 25 - 35
Friday Morning W 10 - 20
Friday Afternoon 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 WSW 20 - 30 SSE 15 - 25 S 30 - 40 WSW 45 - 65
Thursday Night WSW 30 - 40 SW 25 - 35 W 30 - 40 WSW 35 - 50
Friday Morning W 15 - 25 WSW 10 - 20 W 30 - 40 WSW 35 - 50
Friday Afternoon W 5 - 15 W 5 - 15 W 10 - 20 W 10 - 20
Olympics
Date Elevation
Thursday Afternoon WSW 20 - 30
Thursday Night WSW 30 - 40
Friday Morning W 15 - 25
Friday Afternoon W 5 - 15
Friday Night VAR 0 - 10
Northwest Cascades
Date Elevation
Thursday Afternoon SSE 15 - 25
Thursday Night SW 25 - 35
Friday Morning WSW 10 - 20
Friday Afternoon W 5 - 15
Friday Night VAR 0 - 10
Central Cascades
Date Elevation
Thursday Afternoon S 30 - 40
Thursday Night W 30 - 40
Friday Morning W 30 - 40
Friday Afternoon W 10 - 20
Friday Night VAR 0 - 10
South Cascades
Date Elevation
Thursday Afternoon WSW 45 - 65
Thursday Night WSW 35 - 50
Friday Morning WSW 35 - 50
Friday Afternoon W 10 - 20
Friday Night SW 0 - 10
Olympics
Date Direction - Speed
Thursday Afternoon WSW 20 - 30
Thursday Night WSW 30 - 40
Friday Morning W 15 - 25
Friday Afternoon W 5 - 15
Friday Night VAR 0 - 10
Northwest Cascades
Date Direction - Speed
Thursday Afternoon SSE 15 - 25
Thursday Night SW 25 - 35
Friday Morning WSW 10 - 20
Friday Afternoon W 5 - 15
Friday Night VAR 0 - 10
Central Cascades
Date Direction - Speed
Thursday Afternoon S 30 - 40
Thursday Night W 30 - 40
Friday Morning W 30 - 40
Friday Afternoon W 10 - 20
Friday Night VAR 0 - 10
South Cascades
Date Direction - Speed
Thursday Afternoon WSW 45 - 65
Thursday Night WSW 35 - 50
Friday Morning WSW 35 - 50
Friday Afternoon W 10 - 20
Friday Night SW 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 SSW 35 - 50 SSW 45 - 65 SW 55 - 75 SW 65 - 85
Thursday Night WSW 30 - 40 WSW 40 - 60 WSW 50 - 70 WSW 50 - 70
Friday Morning W 20 - 30 W 25 - 35 WNW 35 - 50 W 30 - 40
Friday Afternoon W 10 - 20 WNW 15 - 25 WNW 25 - 35 W 20 - 30
Northwest Cascades
Date Direction - Speed
Thursday Afternoon SSW 35 - 50
Thursday Night WSW 30 - 40
Friday Morning W 20 - 30
Friday Afternoon W 10 - 20
Friday Night WSW 5 - 15
Northeast Cascades
Date Direction - Speed
Thursday Afternoon SSW 45 - 65
Thursday Night WSW 40 - 60
Friday Morning W 25 - 35
Friday Afternoon WNW 15 - 25
Friday Night VAR 0 - 10
Central Cascades
Date Direction - Speed
Thursday Afternoon SW 55 - 75
Thursday Night WSW 50 - 70
Friday Morning WNW 35 - 50
Friday Afternoon WNW 25 - 35
Friday Night W 5 - 15
South Cascades
Date Direction - Speed
Thursday Afternoon SW 65 - 85
Thursday Night WSW 50 - 70
Friday Morning W 30 - 40
Friday Afternoon W 20 - 30
Friday Night WSW 10 - 20

Extended Weather Synopsis for Saturday through Monday

On Saturday, the ridge builds rapidly over the Pacific NW with a ridge axis east of the Cascades. On Saturday night, there's a slight chance of showers as a very weak shortwave trough passes over the ridge. Easterly flow develops Saturday morning and continues through Monday.

On Sunday, the ridge broadens and increases in size to encompass the entire western US and most of western Canada.

On Sunday night through Monday, a deep trough and surface low starts pushing the ridge east with precipitation extending north into our near shore waters and a surface low likely off the coast of California.

 

Extended Weather Forecast for Saturday through Monday

Olympics, Washington Cascades and Mt. Hood Area
Date Weather
Saturday Mostly sunny and unseasonably warm with easterly winds through the passes and slightly cooler temperatures east of the Cascade Crest. Saturday night a mix of clouds and clear skies and a slight chance of a shower. Easterly flow continues. Unseasonably
Sunday Mostly sunny and unseasonably warm. Cooler east of the Cascade Crest. Mostly clear Sunday night with some high clouds arriving. Easterly flow continues.

Snow/Freezing Levels

Date Olympics Northwest Cascades Northeast Cascades Central Cascades South Cascades Easterly Flow in Passes
Saturday Freezing Level 5500' - 6500' 5500' - 6500' 4000' - 5500' 4000' - 6000' 6000' - 7000' *
Saturday Night Freezing Level 6000' - 7000' 6000' - 7000' 4000' - 6000' 6000' - 7000' 7000' - 8000' *
Sunday Freezing Level 7000' - 8000' 7000' - 8000' 6000' - 8000' 7000' - 8000' 7500' - 8500' *
Sunday Night Freezing Level 7500' - 8500' 7500' - 8500' 7000' - 8000' 7000' - 8000' 7500' - 8500' *
Olympics
Date Elevation
Saturday Freezing Level
5500' - 6500'
Easterly Flow*
Saturday Night Freezing Level
6000' - 7000'
Easterly Flow*
Sunday Freezing Level
7000' - 8000'
Easterly Flow*
Sunday Night Freezing Level
7500' - 8500'
Easterly Flow*
Monday Freezing Level
7500' - 8500'
Easterly Flow*
Northwest Cascades
Date Elevation
Saturday Freezing Level
5500' - 6500'
Easterly Flow*
Saturday Night Freezing Level
6000' - 7000'
Easterly Flow*
Sunday Freezing Level
7000' - 8000'
Easterly Flow*
Sunday Night Freezing Level
7500' - 8500'
Easterly Flow*
Monday Freezing Level
7500' - 8500'
Easterly Flow*
Northeast Cascades
Date Elevation
Saturday Freezing Level
4000' - 5500'
Easterly Flow*
Saturday Night Freezing Level
4000' - 6000'
Easterly Flow*
Sunday Freezing Level
6000' - 8000'
Easterly Flow*
Sunday Night Freezing Level
7000' - 8000'
Easterly Flow*
Monday Freezing Level
7500' - 8500'
Easterly Flow*
Central Cascades
Date Elevation
Saturday Freezing Level
4000' - 6000'
Easterly Flow*
Saturday Night Freezing Level
6000' - 7000'
Easterly Flow*
Sunday Freezing Level
7000' - 8000'
Easterly Flow*
Sunday Night Freezing Level
7000' - 8000'
Easterly Flow*
Monday Freezing Level
8000' - 9000'
Easterly Flow*
South Cascades
Date Elevation
Saturday Freezing Level
6000' - 7000'
Easterly Flow*
Saturday Night Freezing Level
7000' - 8000'
Easterly Flow*
Sunday Freezing Level
7500' - 8500'
Easterly Flow*
Sunday Night Freezing Level
7500' - 8500'
Easterly Flow*
Monday Freezing Level
8000' - 9000'
Easterly Flow*

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.