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Mountain Weather Forecast

Issued: 1:34 PM PST Thursday, April 19, 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

A tongue of high pressure is building from over the near shore waters on Thursday, ushered in between the departure of closed low now moving across the southwestern US and a trough over the north-central Pacific. The high pressure is bringing clear skies, light winds and far milder, spring-like conditions. Fair weather cumulus clouds will bring partly to mostly cloudy skies to the mountains, but the atmosphere is generally quite stable.

On Thursday night, the eastward movement of the central Pacific trough will push the high pressure tongue over the Pacific Northwest. Mostly clear skies will allow temperatures to cool overnight on Thursday, but freezing levels will remain elevated.

On Friday, the high pressure will continue to amplify as it moves to the east of our forecast area, while the offshore trough will bring increasing clouds and increasing SW flow aloft, late in the day. Friday will feature warm temperatures that will cool as light winds increase from the W or SW in the afternoon.

On Friday night, the trough will stretch from Alaska to the Northwest tip of Washington State. An associated N-S oriented cold-front will cross the Pacific Northwest shortly after midnight, bringing moderate to occasionally strong crest-level W-SW winds and light to moderate rain and snow becoming showery toward morning. Precipitation will be slightly heavier in the north than the south.

 

 

Weather forecast for Thursday & Friday

Olympics
Date Weather
Thursday Mostly sunny with some fair weather cumulus clouds.
Thursday Night Mostly clear with some high clouds.
Friday Increasing clouds with a chance of light rain or snow late in the day. Mild temperatures.
Cloudy with some light rain and snow. Snow levels gradually lowering.
Washington Cascades near and west of the Crest including Stevens, Snoqualmie and White Passes
Date Weather
Thursday Partly cloudy this afternoon with fair weather cumulus clouds over the topography. Warm.
Thursday Night Mostly clear with increasing high clouds.
Friday Increasing clouds during the day. Warm.
Light to moderate rain and snow, becoming light rain and snow showers by morning. Moderate to occasionally strong crest-level SW or W-SW winds.
East Slopes of the Washington Cascades
Date Weather
Thursday Partly cloudy this afternoon with fair weather cumulus clouds over the topography. Warm.
Thursday Night Mostly clear with increasing high clouds.
Friday Increasing clouds during the day. Warm.
Light rain and snow becoming showery by morning. Snow levels gradually lowering. Moderate to occasionally strong crest-level SW or W-SW winds.
Mt. Hood
Date Weather
Thursday Partly cloudy this afternoon with fair weather cumulus clouds over the topography. Warm.
Thursday Night Mostly clear with increasing high clouds.
Friday Increasing clouds during the day. Warm.
Light rain and snow, mainly after midnight. Snow levels gradually lowering. Moderate to occasionally strong crest-level SW or W-SW winds.

Snow Level/Freezing Level in feet

Date Olympics Northwest Cascades Northeast Cascades Central Cascades South Cascades Easterly Flow in Passes
Thursday Afternoon Freezing Level 6500' 6000' 7000' 7000' 7500'
Thursday Night Freezing Level 6000' 5000' 5500' 6000' 7500'
Friday Morning Freezing Level 5500' 5500' 6000' 7000' 7500'
Friday Afternoon Freezing Level 5000' 6000' 7000' 7000' 8500'
Olympics
Date Elevation
Thursday Afternoon Freezing Level
6500'
Thursday Night Freezing Level
6000'
Friday Morning Freezing Level
5500'
Friday Afternoon Freezing Level
5000'
Friday Night Snow Level
3000'
Northwest Cascades
Date Elevation
Thursday Afternoon Freezing Level
6000'
Thursday Night Freezing Level
5000'
Friday Morning Freezing Level
5500'
Friday Afternoon Freezing Level
6000'
Friday Night Snow Level
3000'
Northeast Cascades
Date Elevation
Thursday Afternoon Freezing Level
7000'
Thursday Night Freezing Level
5500'
Friday Morning Freezing Level
6000'
Friday Afternoon Freezing Level
7000'
Friday Night Snow Level
3500'
Central Cascades
Date Elevation
Thursday Afternoon Freezing Level
7000'
Thursday Night Freezing Level
6000'
Friday Morning Freezing Level
7000'
Friday Afternoon Freezing Level
7000'
Friday Night Snow Level
3500'
South Cascades
Date Elevation
Thursday Afternoon Freezing Level
7500'
Thursday Night Freezing Level
7500'
Friday Morning Freezing Level
7500'
Friday Afternoon Freezing Level
8500'
Friday Night Snow Level
4000'

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

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

Date Direction - Speed
Thursday Afternoon W 5 - 15
Thursday Night VAR 0 - 10
Friday Morning W 0 - 10
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 W 5 - 15 W 5 - 15 W 5 - 15 W 5 - 15
Thursday Night SW 10 - 20 WSW 5 - 15 W 5 - 15 W 5 - 15
Friday Morning SW 15 - 25 SSW 10 - 20 W 5 - 15 W 5 - 15
Friday Afternoon SW 20 - 30 SSW 15 - 25 W 10 - 20 W 10 - 20
Olympics
Date Elevation
Thursday Afternoon W 5 - 15
Thursday Night SW 10 - 20
Friday Morning SW 15 - 25
Friday Afternoon SW 20 - 30
Friday Night SW 25 - 35
Northwest Cascades
Date Elevation
Thursday Afternoon W 5 - 15
Thursday Night WSW 5 - 15
Friday Morning SSW 10 - 20
Friday Afternoon SSW 15 - 25
Friday Night SW 25 - 35
Central Cascades
Date Elevation
Thursday Afternoon W 5 - 15
Thursday Night W 5 - 15
Friday Morning W 5 - 15
Friday Afternoon W 10 - 20
Friday Night WSW 25 - 35
South Cascades
Date Elevation
Thursday Afternoon W 5 - 15
Thursday Night W 5 - 15
Friday Morning W 5 - 15
Friday Afternoon W 10 - 20
Friday Night W 30 - 40
Olympics
Date Direction - Speed
Thursday Afternoon W 5 - 15
Thursday Night SW 10 - 20
Friday Morning SW 15 - 25
Friday Afternoon SW 20 - 30
Friday Night SW 25 - 35
Northwest Cascades
Date Direction - Speed
Thursday Afternoon W 5 - 15
Thursday Night WSW 5 - 15
Friday Morning SSW 10 - 20
Friday Afternoon SSW 15 - 25
Friday Night SW 25 - 35
Central Cascades
Date Direction - Speed
Thursday Afternoon W 5 - 15
Thursday Night W 5 - 15
Friday Morning W 5 - 15
Friday Afternoon W 10 - 20
Friday Night WSW 25 - 35
South Cascades
Date Direction - Speed
Thursday Afternoon W 5 - 15
Thursday Night W 5 - 15
Friday Morning W 5 - 15
Friday Afternoon W 10 - 20
Friday Night W 30 - 40

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 W 10 - 20 WSW 10 - 20 SW 10 - 20 VAR 0 - 10
Thursday Night W 15 - 25 W 10 - 20 W 10 - 20 W 10 - 20
Friday Morning WSW 15 - 25 WSW 10 - 20 WSW 10 - 20 W 15 - 25
Friday Afternoon SW 20 - 30 SW 15 - 25 SW 15 - 25 SW 15 - 25
Northwest Cascades
Date Direction - Speed
Thursday Afternoon W 10 - 20
Thursday Night W 15 - 25
Friday Morning WSW 15 - 25
Friday Afternoon SW 20 - 30
Friday Night SW 45 - 65
Northeast Cascades
Date Direction - Speed
Thursday Afternoon WSW 10 - 20
Thursday Night W 10 - 20
Friday Morning WSW 10 - 20
Friday Afternoon SW 15 - 25
Friday Night WSW 35 - 50
Central Cascades
Date Direction - Speed
Thursday Afternoon SW 10 - 20
Thursday Night W 10 - 20
Friday Morning WSW 10 - 20
Friday Afternoon SW 15 - 25
Friday Night SW 40 - 60
South Cascades
Date Direction - Speed
Thursday Afternoon VAR 0 - 10
Thursday Night W 10 - 20
Friday Morning W 15 - 25
Friday Afternoon SW 15 - 25
Friday Night SW 40 - 60

Extended Weather Synopsis for Saturday through Monday

On Saturday, trough over Washington state will shift east of the forecast area as the associated frontal system exits the region with light rain and snow showers rapidly decreasing during the morning hours leaving isolated shower activity in the central and north Cascades. Skies will clear east of the Cascade crest during the day. 

Saturday night through Monday will feature mostly clear skies, generally light winds, and warming with stronger warming as the high pressure builds more strongly Sunday night into Monday as freezing levels rise to well above crest level by Monday.

Extended Weather Forecast for Saturday through Monday

Olympics, Washington Cascades and Mt. Hood Area
Date Weather
Saturday Decreasing light showers, mainly near and west of the Cascade crest and heaviest in convergence likely developing between Stevens to Snoqualmie Pass. Showers ending by afternoon in the southern part and lingering slightly in the central and north. Clearing skies overnight.
Sunday Mostly sunny on Sunday. Mostly clear on Sunday night. Warming.

Snow/Freezing Levels

Date Olympics Northwest Cascades Northeast Cascades Central Cascades South Cascades Easterly Flow in Passes
Saturday Snow Level 2500' - 3500' 2500' - 3500' 3000' - 4000' 3000' - 4000' 3000' - 4000'
Saturday Night Freezing Level 2500' - 3500' 3000' - 4000' 3500' - 4500' 3000' - 4000' 4500' - 5500'
Sunday Freezing Level 4000' - 6000' 4000' - 6000' 4500' - 6500' 4500' - 6500' 5000' - 7000'
Sunday Night Snow Level 6000' - 8000' 5000' - 6000' 5000' - 6000' 5500' - 6500' 7000' - 8000'
Olympics
Date Elevation
Saturday Snow Level
2500' - 3500'
Saturday Night Freezing Level
2500' - 3500'
Sunday Freezing Level
4000' - 6000'
Sunday Night Snow Level
6000' - 8000'
Monday Snow Level
7500' - 9500'
Northwest Cascades
Date Elevation
Saturday Snow Level
2500' - 3500'
Saturday Night Freezing Level
3000' - 4000'
Sunday Freezing Level
4000' - 6000'
Sunday Night Snow Level
5000' - 6000'
Monday Snow Level
6500' - 8500'
Northeast Cascades
Date Elevation
Saturday Snow Level
3000' - 4000'
Saturday Night Freezing Level
3500' - 4500'
Sunday Freezing Level
4500' - 6500'
Sunday Night Snow Level
5000' - 6000'
Monday Snow Level
5500' - 7500'
Central Cascades
Date Elevation
Saturday Snow Level
3000' - 4000'
Saturday Night Freezing Level
3000' - 4000'
Sunday Freezing Level
4500' - 6500'
Sunday Night Snow Level
5500' - 6500'
Monday Snow Level
7000' - 9000'
South Cascades
Date Elevation
Saturday Snow Level
3000' - 4000'
Saturday Night Freezing Level
4500' - 5500'
Sunday Freezing Level
5000' - 7000'
Sunday Night Snow Level
7000' - 8000'
Monday Snow Level
9000' - 11000'

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.