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Mountain Weather Forecast

Issued: 2:42 PM PST Sunday, March 26, 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 cold front is moving inland, approaching the Cascade crest Sunday afternoon. The heaviest precipitation has been forecast, and is occurring over the Mt Hood area as the front spreads inland. Thus far Sunday, other NWAC stations have had less than impressive precipitation amounts.  Freezing levels have bumped up Sunday afternoon, mainly in response to daytime spring warming. 

Moderate rain an snow will continue into the evening until the front passes, then change to showers overnight and gradually diminish. Freezing levels should lower gradually behind the front overnight.

The associated upper trough should move across the region Monday to shift the flow onshore and maintain active showers through the day, mainly along the west slopes of the Cascades and volcanoes. Less shower activity is expected along the east slopes Monday.

Showers should taper with partial clearing Monday night.

 

Weather forecast for Sunday & Monday

Olympics
Date Weather
Sunday Afternoon

Light to moderate rain and snow. Rain and snow changing to showers, late Sunday afternoon. Moderate alpine winds.

Sunday Night

Diminishing light showers.

Light rain and snow showers with some sun breaks in the afternoon. Diminishing scattered showers overnight with partial clearing.

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

Increasing light to moderate rain and snow, heaviest on the volcanoes.  Rain and snow changing to showers late afternoon or evening. Moderate alpine winds.

Sunday Night

Light to moderate showers, gradually diminishing.

Light to moderate rain and snow showers with some sun breaks in the afternoon. Diminishing light showers overnight with partial clearing.

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

Periods of light to briefly moderate rain and snow. Rain and snow changing to light showers Sunday night and diminishing with partial clearing. Moderate alpine winds.

Scattered showers with sun breaks and partial clearing through the afternoon. Partly cloudy Monday night. 

Mt. Hood Area
Date Weather
Sunday Afternoon - Sunday Night

Moderate rain and snow. Rain and snow changing to showers later Sunday afternoon or evening. Light to moderate showers overnight Sunday, gradually diminishing. Moderate alpine winds.

Light to moderate rain and snow showers with some sun breaks in the afternoon. Diminishing showers overnight with partial clearing.

Snow Level/Freezing Level in feet

Date Olympics Northwest Cascades Northeast Cascades Central Cascades South Cascades Easterly Flow in Passes
Sunday Afternoon Snow Level 4000' 4000' 4000' 4000' 5000' *
Sunday Night - Monday Morning Snow Level 3500' 3500' 3500' 3500' 3500'
Monday Afternoon Snow Level 4000' 4000' 4000' 4000' 4500'
Olympics
Date Elevation
Sunday Afternoon Snow Level
4000'
Easterly Flow*
Sunday Night - Monday Morning Snow Level
3500'
Monday Afternoon Snow Level
4000'
Monday Night Snow Level
3500'
Northwest Cascades
Date Elevation
Sunday Afternoon Snow Level
4000'
Easterly Flow*
Sunday Night - Monday Morning Snow Level
3500'
Monday Afternoon Snow Level
4000'
Monday Night Snow Level
3500'
Northeast Cascades
Date Elevation
Sunday Afternoon Snow Level
4000'
Easterly Flow*
Sunday Night - Monday Morning Snow Level
3500'
Monday Afternoon Snow Level
4000'
Monday Night Snow Level
3500'
Central Cascades
Date Elevation
Sunday Afternoon Snow Level
4000'
Easterly Flow*
Sunday Night - Monday Morning Snow Level
3500'
Monday Afternoon Snow Level
4000'
Monday Night Snow Level
3500'
South Cascades
Date Elevation
Sunday Afternoon Snow Level
5000'
Easterly Flow*
Sunday Night - Monday Morning Snow Level
3500'
Monday Afternoon Snow Level
4500'
Monday Night Snow Level
3500'

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

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

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

Extended Weather Synopsis for Tuesday through Thursday

An approaching warm front is expected to ride over a flat upper ridge along the coast early Tuesday. This should cause increasing rain or snow mainly over the Olympics and NW Washington Cascades with moderately rising snow levels. Warm frontal precipitation should spread south to about the Mt Rainier area Tuesday with little to no precipitation reaching the Mt Hood area Tuesday.

A deepening low pressure system should follow Tuesday night and early Wednesday, bringing much stronger frontal precipitation and more significant warming. This should produce heavy precipitation at significantly rising freezing levels late Tuesday night and Wednesday. The heaviest precipitation with this front should be received over the volcanoes Wednesday. 

An upper trough should pass Wednesday night, causing showers and lowering freezing levels.  Cool NW flow aloft should bring diminishing showers with further cooling early Thursday. 

High pressure should bring drying and clearing later Thursday.

Extended Weather Forecast for Tuesday through Thursday

Olympics, Washington Cascades, Mt Hood
Date Weather
Tuesday

Increasing rain and snow, mainly over the Olympics and west slopes of the WA Cascades from the Mt Baker to Mt Rainier areas.

Cloudy in the southern WA Cascades and Mt Hood area. Moderately rising snow levels.

Wednesday

Moderate to heavy rain and snow, heaviest volcanoes and west slopes Cascades. Further rising freezing levels. Becoming very windy.

Light to moderate rain and snow east slopes Cascades.

Wednesday Night - Thursday Morning

Cooler with light to moderate showers, mainly along the west slopes of the WA Cascades and volcanoes.

Snow/Freezing Levels

Date Olympics Northwest Cascades Northeast Cascades Central Cascades South Cascades Easterly Flow in Passes
Tuesday Morning Snow Level 3000' - 4000' 3000' - 4000' 3000' - 4000' 3000' - 4000' 3000' - 4000'
Tuesday Afternoon - Tuesday Night Snow Level 4500' - 5500' 3500' - 4500' 3000' - 4000' 4000' - 5000' 5000' - 6000'
Wednesday Snow Level 5000' - 6500' 4500' - 5500' 4000' - 5500' 5000' - 6500' 5500' - 7000'
Olympics
Date Elevation
Tuesday Morning Snow Level
3000' - 4000'
Tuesday Afternoon - Tuesday Night Snow Level
4500' - 5500'
Wednesday Snow Level
5000' - 6500'
Wednesday Night - Thursday Snow Level
3000' - 4000'
Northwest Cascades
Date Elevation
Tuesday Morning Snow Level
3000' - 4000'
Tuesday Afternoon - Tuesday Night Snow Level
3500' - 4500'
Wednesday Snow Level
4500' - 5500'
Wednesday Night - Thursday Snow Level
3000' - 4000'
Northeast Cascades
Date Elevation
Tuesday Morning Snow Level
3000' - 4000'
Tuesday Afternoon - Tuesday Night Snow Level
3000' - 4000'
Wednesday Snow Level
4000' - 5500'
Wednesday Night - Thursday Snow Level
3000' - 4000'
Central Cascades
Date Elevation
Tuesday Morning Snow Level
3000' - 4000'
Tuesday Afternoon - Tuesday Night Snow Level
4000' - 5000'
Wednesday Snow Level
5000' - 6500'
Wednesday Night - Thursday Snow Level
3000' - 4000'
South Cascades
Date Elevation
Tuesday Morning Snow Level
3000' - 4000'
Tuesday Afternoon - Tuesday Night Snow Level
5000' - 6000'
Wednesday Snow Level
5500' - 7000'
Wednesday Night - Thursday Snow Level
3500' - 4500'

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.