menu

Mountain Weather Forecast

Issued: 3:44 PM Sunday, December 21, 2014
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

Strong and moist westerly flow is causing orographic showers along the west slope areas and volcanic peaks Sunday afternoon.  A convergence zone is causing slightly heavier showers over the central WA Cascade passes, while stronger flow to the south is causing moderate to heavy periods of rain and snow over the Mt Hood area.

High pressure will build offshore overnight to allow for diminishing showers with the flow weakening and becoming more northwesterly aloft.

A high pressure ridge builds further northward off the coast Monday to allow for a cool and relatively dry Monday, with a chance of a few residual showers possible.

Weather forecast for Sunday & Monday

Olympics
Date Weather
Sunday Afternoon - Sunday Night

Light to occasionally moderate rain and snow showers with a slow cooling trend.  Showers decreasing or ending Sunday night with partial clearing and cooler. 

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

Periods of light to moderate rain and snow with a slow cooling trend.  Occasionally moderate to heavy rain and snow showers Stevens to Snoqualmie Passes in convergence through Sunday evening. Showers gradually decreasing or ending Sunday night with some partial clearing and cooler. 

East slopes of the Washington Cascades
Date Weather
Sunday Afternoon - Sunday Night

Decreasing light rain and snow showers and cooler. Showers ending Sunday night with partial clearing. 

Mt. Hood Area
Date Weather
Sunday Afternoon - Sunday Night

Continued moderate to heavy rain and snow with a slow further cooling trend.  Rain and snow changing to showers and gradually decreasing Sunday night along with further cooling.

Snow Level/Freezing Level in feet

Date Olympics Northwest Cascades Northeast Cascades Central Cascades South Cascades Easterly Flow in Passes
Sunday Afternoon - Sunday Evening Snow Level 4500' 4000' 4000' 4500' 5500'
Sunday Night - Monday Morning Snow Level 3500' 3000' 3000' 3000' 4500'
Olympics
Date Elevation
Sunday Afternoon - Sunday Evening Snow Level
4500'
Sunday Night - Monday Morning Snow Level
3500'
Monday - Monday Night Snow Level
5000'
Northwest Cascades
Date Elevation
Sunday Afternoon - Sunday Evening Snow Level
4000'
Sunday Night - Monday Morning Snow Level
3000'
Monday - Monday Night Snow Level
2500'
Northeast Cascades
Date Elevation
Sunday Afternoon - Sunday Evening Snow Level
4000'
Sunday Night - Monday Morning Snow Level
3000'
Monday - Monday Night Snow Level
1000'
Central Cascades
Date Elevation
Sunday Afternoon - Sunday Evening Snow Level
4500'
Sunday Night - Monday Morning Snow Level
3000'
Monday - Monday Night Snow Level
1500'
South Cascades
Date Elevation
Sunday Afternoon - Sunday Evening Snow Level
5500'
Sunday Night - Monday Morning Snow Level
4500'
Monday - Monday Night Snow Level
6000'

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 .50 - .75 lt .10
Mt Baker Ski Area .50 - .75 lt .10
Washington Pass .50 lt .10
Stevens Pass 1.00 - 1.50 lt .10
Snoqualmie Pass 1.00 - 1.50 lt .10
Mission Ridge lt .25 lt .10
Crystal Mt .50 - .75 lt .10
Paradise 1.00 - 1.50 lt .10
White Pass .75 lt .10
Mt Hood Meadows 2.00 - 3.00 lt .10

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

Date Direction - Speed
Sunday Afternoon - Sunday Night W 10 - 20
Monday 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 Afternoon - Sunday Night WNW 15 - 30 WNW 20 - 30 WNW 20 - 30 WNW 25 - 35
Olympics
Date Elevation
Sunday Afternoon - Sunday Night WNW 15 - 30
Monday - Monday Night WNW 5 - 15
Northwest Cascades
Date Elevation
Sunday Afternoon - Sunday Night WNW 20 - 30
Monday - Monday Night WNW 5 - 15
Central Cascades
Date Elevation
Sunday Afternoon - Sunday Night WNW 20 - 30
Monday - Monday Night WNW 5 - 15
South Cascades
Date Elevation
Sunday Afternoon - Sunday Night WNW 25 - 35
Monday - Monday Night WNW 10 - 20
Olympics
Date Direction - Speed
Sunday Afternoon - Sunday Night WNW 15 - 30
Monday - Monday Night WNW 5 - 15
Northwest Cascades
Date Direction - Speed
Sunday Afternoon - Sunday Night WNW 20 - 30
Monday - Monday Night WNW 5 - 15
Central Cascades
Date Direction - Speed
Sunday Afternoon - Sunday Night WNW 20 - 30
Monday - Monday Night WNW 5 - 15
South Cascades
Date Direction - Speed
Sunday Afternoon - Sunday Night WNW 25 - 35
Monday - Monday Night WNW 10 - 20

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 Afternoon - Sunday Night WNW 20 - 30 WNW 15 - 25 WNW 20 - 30 WNW 30 - 40
Northwest Cascades
Date Direction - Speed
Sunday Afternoon - Sunday Night WNW 20 - 30
Monday - Monday Night NW 10 - 20
Northeast Cascades
Date Direction - Speed
Sunday Afternoon - Sunday Night WNW 15 - 25
Monday - Monday Night NW 10 - 20
Central Cascades
Date Direction - Speed
Sunday Afternoon - Sunday Night WNW 20 - 30
Monday - Monday Night NW 10 - 20
South Cascades
Date Direction - Speed
Sunday Afternoon - Sunday Night WNW 30 - 40
Monday - Monday Night NW 20 - 30

Extended Weather Synopsis for Tuesday through Thursday

The ridge moves inland by early Tuesday as moisture begins to affect the Olympics and NW  Washington Cascades by early Tuesday. This rain and snow should increase in those areas later Tuesday along with warming. 

The central and south part remains relatively dry Tuesday before the frontal moisture increases and spreads over the entire region Wednesday. This should be caused by an enhanced upper trough, expected to shift across the PNW later Wednesday.

High pressure and cool northwest flow is expected Thursday, following the trough and frontal moisture Wednedsay.

Extended Weather Forecast for Tuesday through Thursday

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

Light to moderate rain and snow Olympics and NW Cascades. Occasional light rain and snow central part and cloudy south part. 

Tuesday Night

Increasing light to moderate rain and snow.

Wednesday - Wednesday Night

Further increasing rain and snow becoming moderate to briefly heavy.

East slopes of the Washington Cascades
Date Weather
Tuesday - Tuesday Night

Light rain and snow beginning north part shifting south late. 

Wednesday - Wednesday Night

Periods of light to moderate rain and snow changing to showers late.

Mt. Hood Area
Date Weather
Tuesday - Wednesday Morning

Mostly cloudy with light rain and snow developing by early Wednesday.

Wednesday Afternoon - Wednesday Night

Moderate rain and snow changing to showers and decreasing Wednesday night. 

Snow/Freezing Levels

Date Olympics Northwest Cascades Northeast Cascades Central Cascades South Cascades Easterly Flow in Passes
Tuesday - Night Snow Level 5500' - 6500' 5000' - 6000' 4500' - 5500' 5500' - 6500' 7000' - 8000'
Wednesday - Night Snow Level 2000' - 3000' 2000' - 3000' 3000' - 4000' 4000' - 5000' 5000' - 6000'
Olympics
Date Elevation
Tuesday - Night Snow Level
5500' - 6500'
Wednesday - Night Snow Level
2000' - 3000'
Wednesday Night - Thursday Night Snow Level
2000' - 3000'
Northwest Cascades
Date Elevation
Tuesday - Night Snow Level
5000' - 6000'
Wednesday - Night Snow Level
2000' - 3000'
Wednesday Night - Thursday Night Snow Level
2000' - 3000'
Northeast Cascades
Date Elevation
Tuesday - Night Snow Level
4500' - 5500'
Wednesday - Night Snow Level
3000' - 4000'
Wednesday Night - Thursday Night Snow Level
2000' - 3000'
Central Cascades
Date Elevation
Tuesday - Night Snow Level
5500' - 6500'
Wednesday - Night Snow Level
4000' - 5000'
Wednesday Night - Thursday Night Snow Level
2000' - 3000'
South Cascades
Date Elevation
Tuesday - Night Snow Level
7000' - 8000'
Wednesday - Night Snow Level
5000' - 6000'
Wednesday Night - Thursday Night Snow Level
2000' - 3000'

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.