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Mountain Weather Forecast

Issued: 4:32 PM PST Sunday, November 19, 2017
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 Sunday & Monday

A Pacific front is spreading, increasing winds and precipitation across the Olympics to about the Mt Baker area Sunday afternoon. The front should sag across the remainder of the forecast area overnight, causing increasing winds and precipitation to reach all areas, especially those favoring SSW flow aloft, such as the volcanoes and Crystal Mountain area. Precipitation should diminish rapidly behind the front as it shifts south and east. The diminishing precipitation should shift from north to south late Sunday night and early Monday.  Most areas will see periods of heavy precipitation with the frontal passage with less precipitation over the east slopes of the Cascades.

Freezing levels are not expected to rise significantly across the Olympics and north WA Cascades, but a tongue of warmer air should spread from the Mt Hood area to about the Mt Rainier area by early Monday, causing rising freezing levels from the south-central Cascades southward to Mt Hood.

The front may stall across the Mt Hood area Monday to maintain periods of heavy precipitation at rather mild temperatures. Elsewhere in the Olympics and WA Cascades, most areas should see a lull between system on Monday with cooling.

A deep upper level low and associated trough well offshore should build a brief ridge over the area Monday night to cause warming. This will set the stage for a period of increasingly strong SSW flow aloft and bring a series of warm and wet weather impulses beginning Tuesday. 

Weather forecast for Sunday & Monday

Olympics
Date Weather
Sunday Night

Heavy rain and snow changing to showers and rapidly diminishing by midnight. Showers ending with partial clearing after midnight.

Monday

Cloudy with diminishing light rain and snow showers.

Cloudy with increasing light to moderate rain and snow after midnight. Warming with increasing strong winds.

Washington Cascades near and west of the crest including Stevens, Snoqualmie, and White Passes
Date Weather
Sunday Night

Heavy rain and snow north part spreading to all areas overnight. Rain and snow changing to showers in the north near midnight and diminishing. Rain and snow changing to showers and gradually decreasing in the central late. Moderate to heavy rain and snow persisting in the south WA Cascades. 

Monday

Cloudy with scattered showers north part. Light to moderate showers, central part early, diminishing in the afternoon.  Moderate to heavy rain and snow in the south part.

Cloudy with increasing light to moderate rain and snow after midnight. Warming with increasing strong winds.

East slopes of the Washington Cascades
Date Weather
Sunday Night

Cloudy with increasing light to moderate rain and snow after midnight. Increasing strong winds, warming in the south part.

Monday

Mostly cloudy with scattered light showers north and central. Light to occasional moderate showers south part. 

Cloudy with light rain and snow spreading northward late with warming and increasing winds.

Mt. Hood Area
Date Weather
Sunday Night

Cloudy early, but becoming stormy overnight with heavy rain and snow, strong winds and rising freezing levels. 

Monday

Moderate to heavy rain and snow and windy. Continued warming.

Briefly diminishing showers early. Increasing moderate to heavy rain and snow after midnight. 

Snow Level/Freezing Level in feet

Date Olympics Northwest Cascades Northeast Cascades Central Cascades South Cascades Easterly Flow in Passes
Sunday Evening Snow Level 5000' 4000' 3500' 4500' 6000' *
Sunday Night Snow Level 6000' 4000' 3500' 5500' 7000' *
Monday Snow Level 2500' 2500' 4000' 3500' 6000'
Monday Afternoon Snow Level 3000' 2500' 2500' 4500' 7000'
Olympics
Date Elevation
Sunday Evening Snow Level
5000'
Easterly Flow*
Sunday Night Snow Level
6000'
Easterly Flow*
Monday Snow Level
2500'
Monday Afternoon Snow Level
3000'
Monday Night Snow Level
6000'
Easterly Flow*
Northwest Cascades
Date Elevation
Sunday Evening Snow Level
4000'
Easterly Flow*
Sunday Night Snow Level
4000'
Easterly Flow*
Monday Snow Level
2500'
Monday Afternoon Snow Level
2500'
Monday Night Snow Level
4500'
Easterly Flow*
Northeast Cascades
Date Elevation
Sunday Evening Snow Level
3500'
Easterly Flow*
Sunday Night Snow Level
3500'
Easterly Flow*
Monday Snow Level
4000'
Monday Afternoon Snow Level
2500'
Monday Night Snow Level
4500'
Easterly Flow*
Central Cascades
Date Elevation
Sunday Evening Snow Level
4500'
Easterly Flow*
Sunday Night Snow Level
5500'
Easterly Flow*
Monday Snow Level
3500'
Monday Afternoon Snow Level
4500'
Monday Night Snow Level
7000'
Easterly Flow*
South Cascades
Date Elevation
Sunday Evening Snow Level
6000'
Easterly Flow*
Sunday Night Snow Level
7000'
Easterly Flow*
Monday Snow Level
6000'
Monday Afternoon Snow Level
7000'
Monday Night Snow Level
9000'
Easterly Flow*

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

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

Date Direction - Speed
Sunday Evening E 5 - 15
Sunday Night E 5 - 10
Monday W 5 - 15
Monday Afternoon W 0 - 10

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
Sunday Evening SSW 35 - 50 SSW 30 - 40 SSW 30 - 40 SW 30 - 40
Sunday Night WSW 10 - 20 SW 10 - 20 SW 35 - 50 SW 35 - 50
Monday WSW 5 - 15 WSW 5 - 15 WSW 10 - 20 WSW 15 - 25
Monday Afternoon S 5 - 10 SSE 5 - 10 WSW 10 - 20 WSW 15 - 25
Olympics
Date Elevation
Sunday Evening SSW 35 - 50
Sunday Night WSW 10 - 20
Monday WSW 5 - 15
Monday Afternoon S 5 - 10
Monday Night S 15 - 30
Northwest Cascades
Date Elevation
Sunday Evening SSW 30 - 40
Sunday Night SW 10 - 20
Monday WSW 5 - 15
Monday Afternoon SSE 5 - 10
Monday Night SSE 10 - 20
Central Cascades
Date Elevation
Sunday Evening SSW 30 - 40
Sunday Night SW 35 - 50
Monday WSW 10 - 20
Monday Afternoon WSW 10 - 20
Monday Night SSW 10 - 20
South Cascades
Date Elevation
Sunday Evening SW 30 - 40
Sunday Night SW 35 - 50
Monday WSW 15 - 25
Monday Afternoon WSW 15 - 25
Monday Night SSW 15 - 30
Olympics
Date Direction - Speed
Sunday Evening SSW 35 - 50
Sunday Night WSW 10 - 20
Monday WSW 5 - 15
Monday Afternoon S 5 - 10
Monday Night S 15 - 30
Northwest Cascades
Date Direction - Speed
Sunday Evening SSW 30 - 40
Sunday Night SW 10 - 20
Monday WSW 5 - 15
Monday Afternoon SSE 5 - 10
Monday Night SSE 10 - 20
Central Cascades
Date Direction - Speed
Sunday Evening SSW 30 - 40
Sunday Night SW 35 - 50
Monday WSW 10 - 20
Monday Afternoon WSW 10 - 20
Monday Night SSW 10 - 20
South Cascades
Date Direction - Speed
Sunday Evening SW 30 - 40
Sunday Night SW 35 - 50
Monday WSW 15 - 25
Monday Afternoon WSW 15 - 25
Monday Night SSW 15 - 30

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
Sunday Evening SW 60 - 80 SW 60 - 80 SW 50 - 70 SW 50 - 70
Sunday Night SW 40 - 60 SW 40 - 60 SW 60 - 80 SW 60 - 80
Monday SW 20 - 30 SW 20 - 30 SW 40 - 60 WSW 50 - 70
Monday Afternoon SW 20 - 30 SW 20 - 30 SW 40 - 60 WSW 50 - 70
Northwest Cascades
Date Direction - Speed
Sunday Evening SW 60 - 80
Sunday Night SW 40 - 60
Monday SW 20 - 30
Monday Afternoon SW 20 - 30
Monday Night WSW 25 - 35
Northeast Cascades
Date Direction - Speed
Sunday Evening SW 60 - 80
Sunday Night SW 40 - 60
Monday SW 20 - 30
Monday Afternoon SW 20 - 30
Monday Night WSW 25 - 35
Central Cascades
Date Direction - Speed
Sunday Evening SW 50 - 70
Sunday Night SW 60 - 80
Monday SW 40 - 60
Monday Afternoon SW 40 - 60
Monday Night SW 40 - 60
South Cascades
Date Direction - Speed
Sunday Evening SW 50 - 70
Sunday Night SW 60 - 80
Monday WSW 50 - 70
Monday Afternoon WSW 50 - 70
Monday Night SW 35 - 50

Extended Weather Synopsis for Tuesday through Thursday

Increasing warm and very moist SSW flow Tuesday, should persist into Thanksgiving Day as a deep low pressure system develops in the eastern North Pacific. 

This pattern should produce periods of heavy precipitation at high freezing levels through the extended period. The heaviest precipitation is expected over the volcanoes Tuesday through Thursday. 

Extended Weather Forecast for Tuesday through Thursday

Olympics, Washington Cascades, and Mt. Hood
Date Weather
Tuesday - Tuesday Night

Stormy with increasing heavy rain and snow, very strong crest level winds and rapidly rising freezing levels. Heaviest precipitation expected over the volcanoes and areas exposed to southerly flow. 

Wednesday - Wednesday Night

Periods of moderate to heavy rain and snow, remaining mild. The heaviest precipitation expected over the volcanoes. 

Snow/Freezing Levels

Date Olympics Northwest Cascades Northeast Cascades Central Cascades South Cascades Easterly Flow in Passes
Tuesday Snow Level 8000' - 10000' 6000' - 9000' 6000' - 9000' 7500' - 10000' 9000' - 11000'
Tuesday Night Snow Level 8000' - 10000' 7500' - 9000' 7500' - 9000' 8000' - 9500' 9000' - 11000'
Wednesday Snow Level 9000' - 10000' 9000' - 10000' 8500' - 9500' 9000' - 10000' 9500' - 11000'
Wednesday Night Snow Level 8000' - 9500' 8000' - 9500' 8000' - 9500' 8000' - 9500' 8500' - 10000'
Olympics
Date Elevation
Tuesday Snow Level
8000' - 10000'
Tuesday Night Snow Level
8000' - 10000'
Wednesday Snow Level
9000' - 10000'
Wednesday Night Snow Level
8000' - 9500'
Thursday Snow Level
5000' - 7000'
Northwest Cascades
Date Elevation
Tuesday Snow Level
6000' - 9000'
Tuesday Night Snow Level
7500' - 9000'
Wednesday Snow Level
9000' - 10000'
Wednesday Night Snow Level
8000' - 9500'
Thursday Snow Level
5000' - 8000'
Northeast Cascades
Date Elevation
Tuesday Snow Level
6000' - 9000'
Tuesday Night Snow Level
7500' - 9000'
Wednesday Snow Level
8500' - 9500'
Wednesday Night Snow Level
8000' - 9500'
Thursday Snow Level
6000' - 8000'
Central Cascades
Date Elevation
Tuesday Snow Level
7500' - 10000'
Tuesday Night Snow Level
8000' - 9500'
Wednesday Snow Level
9000' - 10000'
Wednesday Night Snow Level
8000' - 9500'
Thursday Snow Level
6000' - 8000'
South Cascades
Date Elevation
Tuesday Snow Level
9000' - 11000'
Tuesday Night Snow Level
9000' - 11000'
Wednesday Snow Level
9500' - 11000'
Wednesday Night Snow Level
8500' - 10000'
Thursday Snow Level
7000' - 9000'

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.