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Mountain Weather Forecast

Issued: 7:33 AM 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 comma-shaped surface/upper low sit off the Washington Coast on Thursday morning. The low will track NE to Cape Flattery by around noon, bringing moderate rain and snow to the mountains. Most locations in the Cascades will see 1-2 inches of water out of this storm

Moderate free air winds (and stronger gusts) will be out of the south today, switching to SW this evening, then westerly behind the front, which should pass the Cascades slightly before midnight. Temperatures will drop sharply behind the front and most locations will change back to snow as precipitation intensities are decreasing.

Snoqualmie at pass level should see a changeover to rain in the late morning or early afternoon with a changeover back to Snow between 2 and 4 AM on Friday. The majority of the precipitation here will fall as rain. Stevens Pass should only see a brief period of rain during the evening hours. Mt. Baker base is likely to have rain mixing with snow while the top of the mountain stays Snow throughout the event.

On Thursday night, precipitation should decrease behind the 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 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 Morning Snow Level 3500' 4000' 3500' 3500' 4000' *
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 Morning Snow Level
3500'
Easterly Flow*
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 Morning Snow Level
4000'
Easterly Flow*
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 Morning Snow Level
3500'
Easterly Flow*
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 Morning Snow Level
3500'
Easterly Flow*
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 Morning Snow Level
4000'
Easterly Flow*
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 .25 - .50 lt .10
Mt Baker Ski Area 1.00 - 1.50 lt .10
Washington Pass 1.00 lt .10
Stevens Pass 1.00 .25
Snoqualmie Pass 1.50 lt .25
Mission Ridge .25 - .50 lt .10
Crystal Mt 1.00 - 1.50 lt .10
Paradise 2.00 lt .10
White Pass 1.00 lt .10
Mt Hood Meadows 1.00 - 1.50 lt .10

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

Date Direction - Speed
Thursday Morning E 20 - 30
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 Morning SSE 25 - 35 SSE 15 - 25 ESE 30 - 40 SSW 50 - 70
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 Morning SSE 25 - 35
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 Morning SSE 15 - 25
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 Morning ESE 30 - 40
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 Morning SSW 50 - 70
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 Morning SSE 25 - 35
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 Morning SSE 15 - 25
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 Morning ESE 30 - 40
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 Morning SSW 50 - 70
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 Morning S 30 - 40 S 20 - 30 SSW 65 - 85 SW 65 - 85
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 Morning S 30 - 40
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 Morning S 20 - 30
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 Morning SSW 65 - 85
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 Morning SW 65 - 85
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

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.