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Mountain Weather Forecast

Issued: 2:52 PM PST Saturday, February 17, 2018
by Dennis D'Amico

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 Saturday & Sunday

Afternoon update: Slight changes to precipitation forecasts for Day 1 and Day 2. If you're out in the mountains from late morning onward Saturday, you know it's been exceptionally windy with strong west winds seen at all elevations and at most stations. On Saturday, several NWAC stations gusted over 100 mph earlier today: White Pass, Camp Muir, Mission Ridge, Cascade Express-Hood. 

Prev discussion: Our active pattern continues with the second low pressure system in 24 hours for the Pacific Northwest sliding down over the area in NW flow aloft. Precipitation has become moderate to locally heavy over the Cascade Passes this morning and precipitation rates in general should increase through the early afternoon hours.  The low pressure center currently off the northern tip of Vancouver Island will pass into southern British Columbia this afternoon with the trailing front passing through the Cascades in the early afternoon. A swath of warmer air will push into the mountains from about Stevens Pass to Mt. Hood, with the north Cascades having a more muted warming trend. Snow levels should peak around 6000 ft at Mt. Hood, 4500 ft in the Crystal Paradise/Mt. Rainier area and 4000 feet for Stevens/Snoqualmie Pass mid-day. During and following the frontal passage westerly winds will be strong, but most pronounced from Snoqualmie Pass and southward. Expect sharp cooling this afternoon behind the front. 

The quasi-stationary Pacific upper level ridge parked offshore will retrograde to 145W Saturday night and Sunday. This will open the door for the coldest air of the season to begin to infiltrate from the interior.  As the upper level trough digs over the Pacific Northwest and northern California Sunday, a weak surface low pressure system off the Washington/Oregon coast will invigorate snow shower activity for the Mt. Hood area and the south Washington Cascades while a slow drying trend takes place over the northwest and central-west Cascades. Colder air being drawn across the Strait of Juan de Fuca will lead to upslope snow showers in the Hurricane Ridge area. Upslope snow showers also look likely along the east slopes of the Cascades on Sunday with significant accumulations potential for Mission Ridge.

Shower activity will wane Sunday night as the trough digs over the intermountain West and the flow aloft turns northerly. 

Weather forecast for Saturday & Sunday

Olympics
Date Weather
Saturday Light to moderate rain and snow. Warming trend peaking mid-day. Showers and strong cooling trend mid-afternoon. Becoming windy.
Saturday Night Light to occasionally moderate snow showers. Strong cooling trend. Winds decreasing overnight.
Sunday Light to occasionally moderate snow showers in the morning along the north slopes of the Olympics becoming scattered in the afternoon. Cold.
Partly cloudy with isolated light snow showers. Cold.
Washington Cascades near and west of the Crest including Stevens, Snoqualmie and White Passes
Date Weather
Saturday Stormy. Warming trend strongest from Stevens Pass to White Pass, peaking mid-day. Showers and strong cooling trend late afternoon. Very windy.
Saturday Night Light to occasionally moderate snow showers. Strong cooling trend. Winds decreasing overnight.
Sunday Mostly cloudy with scattered snow showers in the north Cascades. Light snow showers central and south. Cold.
Partly cloudy with isolated light snow showers. Cold.
East Slopes of the Washington Cascades
Date Weather
Saturday Light to moderate rain and snow. Warming trend strongest from Stevens Pass to White Pass, peaking mid-day. Light to moderate showers and strong cooling trend late afternoon. Very windy.
Saturday Night Light to moderate snow showers. Strong cooling trend. Winds decreasing overnight.
Sunday Light to moderate snow showers in the morning becoming scattered in the afternoon. Cold.
Partly cloudy with isolated light snow showers. Cold.
Mt. Hood
Date Weather
Saturday Stormy. Warming trend peaking mid-day. Showers and cooling trend late afternoon. Very windy.
Saturday Night Light to occasionally moderate snow showers. Strong cooling trend.
Sunday Light to moderate snow showers. Cold. Winds decreasing.
Mostly to partly cloudy with isolated light snow showers. Cold.

Snow Level/Freezing Level in feet

Date Olympics Northwest Cascades Northeast Cascades Central Cascades South Cascades Easterly Flow in Passes
Saturday Mid-day Snow Level 5000' 3000' 2500' 4000' 6000'
Saturday Afternoon Snow Level 3000' 2500' 3000' 2500' 4500'
Saturday Night Snow Level 2000' 2000' 2000' 2000' 3000'
Sunday Morning Snow Level 1000' 1000' 500' 1000' 2500'
Sunday Afternoon Snow Level 0' 0' 0' 500' 1000'
Olympics
Date Elevation
Saturday Mid-day Snow Level
5000'
Saturday Afternoon Snow Level
3000'
Saturday Night Snow Level
2000'
Sunday Morning Snow Level
1000'
Sunday Afternoon Snow Level
0'
Sunday Night Snow Level
0'
Northwest Cascades
Date Elevation
Saturday Mid-day Snow Level
3000'
Saturday Afternoon Snow Level
2500'
Saturday Night Snow Level
2000'
Sunday Morning Snow Level
1000'
Sunday Afternoon Snow Level
0'
Sunday Night Snow Level
0'
Northeast Cascades
Date Elevation
Saturday Mid-day Snow Level
2500'
Saturday Afternoon Snow Level
3000'
Saturday Night Snow Level
2000'
Sunday Morning Snow Level
500'
Sunday Afternoon Snow Level
0'
Sunday Night Snow Level
0'
Central Cascades
Date Elevation
Saturday Mid-day Snow Level
4000'
Saturday Afternoon Snow Level
2500'
Saturday Night Snow Level
2000'
Sunday Morning Snow Level
1000'
Sunday Afternoon Snow Level
500'
Sunday Night Snow Level
0'
South Cascades
Date Elevation
Saturday Mid-day Snow Level
6000'
Saturday Afternoon Snow Level
4500'
Saturday Night Snow Level
3000'
Sunday Morning Snow Level
2500'
Sunday Afternoon Snow Level
1000'
Sunday Night Snow Level
0'

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 Sun Mon
Hurricane Ridge 1.00 .25 - .50
Mt Baker Ski Area 1.00 - 1.50 lt .10
Washington Pass 1.00 - 1.50 lt .25
Stevens Pass 1.50 - 2.00 lt .25
Snoqualmie Pass 2.00 .25
Mission Ridge .50 - .75 .50
Crystal Mt 1.00 .25
Paradise 2.00 - 2.50 .50
White Pass 1.50 .25 - .50
Mt Hood Meadows 2.50 .75 - 1.00

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

Date Direction - Speed
Saturday Afternoon W 30 - 40
Saturday Night W 15 - 25
Sunday Morning W 5 - 15
Sunday Afternoon E 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
Saturday Afternoon WSW 25 - 35 SW 20 - 30 WSW 35 - 55 SW 45 - 55
Saturday Night WSW 15 - 25 SW 10 - 20 SW 25 - 35 WSW 25 - 35
Sunday Morning NNE 10 - 20 NE 10 - 20 SW 10 - 20 SW 15 - 30
Sunday Afternoon NNE 15 - 25 NE 10 - 20 NW 5 - 15 VAR 5 - 15
Olympics
Date Elevation
Saturday Afternoon WSW 25 - 35
Saturday Night WSW 15 - 25
Sunday Morning NNE 10 - 20
Sunday Afternoon NNE 15 - 25
Sunday Night NNE 15 - 25
Northwest Cascades
Date Elevation
Saturday Afternoon SW 20 - 30
Saturday Night SW 10 - 20
Sunday Morning NE 10 - 20
Sunday Afternoon NE 10 - 20
Sunday Night NE 10 - 20
Central Cascades
Date Elevation
Saturday Afternoon WSW 35 - 55
Saturday Night SW 25 - 35
Sunday Morning SW 10 - 20
Sunday Afternoon NW 5 - 15
Sunday Night E 0 - 10
South Cascades
Date Elevation
Saturday Afternoon SW 45 - 55
Saturday Night WSW 25 - 35
Sunday Morning SW 15 - 30
Sunday Afternoon VAR 5 - 15
Sunday Night E 5 - 15
Olympics
Date Direction - Speed
Saturday Afternoon WSW 25 - 35
Saturday Night WSW 15 - 25
Sunday Morning NNE 10 - 20
Sunday Afternoon NNE 15 - 25
Sunday Night NNE 15 - 25
Northwest Cascades
Date Direction - Speed
Saturday Afternoon SW 20 - 30
Saturday Night SW 10 - 20
Sunday Morning NE 10 - 20
Sunday Afternoon NE 10 - 20
Sunday Night NE 10 - 20
Central Cascades
Date Direction - Speed
Saturday Afternoon WSW 35 - 55
Saturday Night SW 25 - 35
Sunday Morning SW 10 - 20
Sunday Afternoon NW 5 - 15
Sunday Night E 0 - 10
South Cascades
Date Direction - Speed
Saturday Afternoon SW 45 - 55
Saturday Night WSW 25 - 35
Sunday Morning SW 15 - 30
Sunday Afternoon VAR 5 - 15
Sunday Night E 5 - 15

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
Saturday Afternoon WSW 40 - 50 WSW 35 - 45 WSW 65 - 80 WSW 65 - 80
Saturday Night SW 15 - 25 W 20 - 30 WSW 30 - 40 WSW 40 - 50
Sunday Morning NE 10 - 20 N 10 - 20 NW 5 - 15 WSW 25 - 40
Sunday Afternoon NE 15 - 25 NNE 15 - 25 NW 10 - 20 W 20 - 30
Northwest Cascades
Date Direction - Speed
Saturday Afternoon WSW 40 - 50
Saturday Night SW 15 - 25
Sunday Morning NE 10 - 20
Sunday Afternoon NE 15 - 25
Sunday Night NE 15 - 25
Northeast Cascades
Date Direction - Speed
Saturday Afternoon WSW 35 - 45
Saturday Night W 20 - 30
Sunday Morning N 10 - 20
Sunday Afternoon NNE 15 - 25
Sunday Night NNE 15 - 25
Central Cascades
Date Direction - Speed
Saturday Afternoon WSW 65 - 80
Saturday Night WSW 30 - 40
Sunday Morning NW 5 - 15
Sunday Afternoon NW 10 - 20
Sunday Night N 0 - 10
South Cascades
Date Direction - Speed
Saturday Afternoon WSW 65 - 80
Saturday Night WSW 40 - 50
Sunday Morning WSW 25 - 40
Sunday Afternoon W 20 - 30
Sunday Night NW 5 - 15

Extended Weather Synopsis for Monday through Wednesday

We will be in the familiar position of N-NW flow aloft Monday through Wednesday with an upper ridge positioned offshore around 145W and longwave troughing over the intermountain West shifting to the Rockies. However, modified arctic air will be entrenched over the Olympics and Cascades for the first half of the week. Hard to time shortwaves in NW flow will approach the area Tuesday and Wednesday, potentially bringing a quick shot of light snow to the region. Alpine winds out of the north will be the a persistent feature during this period as well. 

Extended Weather Forecast for Monday through Wednesday

Olympics, Washington Cascades and Mt. Hood Area
Date Weather
Monday Partly to mostly clear. Cold.
Tuesday Fair. Cold.

Snow/Freezing Levels

Date Olympics Northwest Cascades Northeast Cascades Central Cascades South Cascades Easterly Flow in Passes
Monday Snow Level 0' - 0' 0' - 0' 0' - 0' 0' - 0' 0' - 0'
Monday Night Snow Level 0' - 0' 0' - 0' 0' - 0' 0' - 0' 0' - 0'
Tuesday Snow Level 0' - 0' 0' - 0' 0' - 0' 0' - 0' 0' - 0'
Tuesday Night Snow Level 0' - 0' 0' - 0' 0' - 0' 0' - 0' 0' - 0'
Olympics
Date Elevation
Monday Snow Level
0' - 0'
Monday Night Snow Level
0' - 0'
Tuesday Snow Level
0' - 0'
Tuesday Night Snow Level
0' - 0'
Wednesday Snow Level
0' - 1000'
Northwest Cascades
Date Elevation
Monday Snow Level
0' - 0'
Monday Night Snow Level
0' - 0'
Tuesday Snow Level
0' - 0'
Tuesday Night Snow Level
0' - 0'
Wednesday Snow Level
0' - 1000'
Northeast Cascades
Date Elevation
Monday Snow Level
0' - 0'
Monday Night Snow Level
0' - 0'
Tuesday Snow Level
0' - 0'
Tuesday Night Snow Level
0' - 0'
Wednesday Snow Level
0' - 1000'
Central Cascades
Date Elevation
Monday Snow Level
0' - 0'
Monday Night Snow Level
0' - 0'
Tuesday Snow Level
0' - 0'
Tuesday Night Snow Level
0' - 0'
Wednesday Snow Level
0' - 1000'
South Cascades
Date Elevation
Monday Snow Level
0' - 0'
Monday Night Snow Level
0' - 0'
Tuesday Snow Level
0' - 0'
Tuesday Night Snow Level
0' - 0'
Wednesday Snow Level
500' - 1500'

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.