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Mountain Weather Forecast

Issued: 2:35 PM PST Monday, February 5, 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 Monday & Tuesday

Snow levels will gradually fall overnight and settle around 4000 feet on Monday.  A quasi-stationary band of rain and snow re-developed mid-day and will continue to focus rain and snow on the west slopes of the Cascades, mainly from the central Cascades northward on a W-NW flow. Light new snowfall accumulations expected above 4000 feet for Snoqualmie Pass to Mt. Baker. Increasingly light precipitation should spread southward overnight Monday on a weakening flow.

NW flow will keep plenty of moisture and clouds banked up along the west slopes of the Cascades Monday and Monday night, with Hurricane Ridge, Hood, and the east slopes potentially breaking into clear skies at times. The ridge will amplify offshore on Monday and begin to slide back towards the PNW Monday night, helping to decrease shower activity.

On Tuesday, the ridge slides further east, further decreasing the already light shower activity. During the afternoon, a weak surface feature begins to spread light rain to the North Cascades with light precipitation increasing slightly Tuesday night in the Olympics and North Cascades.

Tuesday night, a weak shortwave sliding over the offshore ridge will pass mostly north of Washington state, keeping showers in the forecast for the northern portions of the Cascades as areas further south remain drier. The shortwave will increase W winds into the moderate range.

Weather forecast for Monday & Tuesday

Olympics
Date Weather
Monday Cloudy, chance of light rain or snow showers.
Monday Night Cloudy, chance of a light rain or snow shower.
Tuesday Cloudy, chance of light rain or snow.
Increasing light rain or snow before midnight; decreasing after midnight.
Washington Cascades near and west of the Crest including Stevens, Snoqualmie and White Passes
Date Weather
Monday Light rain and snow from the central Cascades northward; heaviest in convergence and away from the crest. Elsewhere, mostly cloudy with a chance of light rain or snow showers.
Monday Night Decreasing light rain and snow showers, with rain and snow showers focused on the central Cascades.
Tuesday Light rain and snow, central and mainly north Cascades. Cloudy south Cascades.
Light to occasional moderate rain and snow central and north; heaviest near the Canadian border.
East Slopes of the Washington Cascades
Date Weather
Monday Light rain and snow at higher elevations, heaviest central and north. Cloudy near the Cascade crest with mostly sunny skies east of the Cascade crest.
Monday Night Decreasing Light rain and snow, heaviest central and north. Cloudy near the Cascade crest with mostly clear skies east of the Cascade crest.
Tuesday A few showers lingering in the morning at high elevations, north and central parts. Increasing light rain and snow in the north at high elevations in the afternoon. Cloudy near the Cascade crest with mostly clear skies east of the Cascade crest.
Very light rain and snow at high elevations, north and central parts.
Mt. Hood
Date Weather
Monday Partly cloudy.
Monday Night Partly clear.
Tuesday Partly cloudy.
Partly clear.

Snow Level/Freezing Level in feet

Date Olympics Northwest Cascades Northeast Cascades Central Cascades South Cascades Easterly Flow in Passes
Monday Afternoon Snow Level 4000' 3500' 4000' 3500' 4000'
Monday Night Snow Level 4000' 3500' 2500' 3000' 3500'
Tuesday Morning Snow Level 5000' 3500' 4000' 3000' 4000'
Tuesday Afternoon Snow Level 5000' 3500' 4000' 3500' 7500'
Olympics
Date Elevation
Monday Afternoon Snow Level
4000'
Monday Night Snow Level
4000'
Tuesday Morning Snow Level
5000'
Tuesday Afternoon Snow Level
5000'
Tuesday Night Snow Level
6000'
Northwest Cascades
Date Elevation
Monday Afternoon Snow Level
3500'
Monday Night Snow Level
3500'
Tuesday Morning Snow Level
3500'
Tuesday Afternoon Snow Level
3500'
Tuesday Night Snow Level
4500'
Northeast Cascades
Date Elevation
Monday Afternoon Snow Level
4000'
Monday Night Snow Level
2500'
Tuesday Morning Snow Level
4000'
Tuesday Afternoon Snow Level
4000'
Tuesday Night Snow Level
4000'
Central Cascades
Date Elevation
Monday Afternoon Snow Level
3500'
Monday Night Snow Level
3000'
Tuesday Morning Snow Level
3000'
Tuesday Afternoon Snow Level
3500'
Tuesday Night Snow Level
4500'
South Cascades
Date Elevation
Monday Afternoon Snow Level
4000'
Monday Night Snow Level
3500'
Tuesday Morning Snow Level
4000'
Tuesday Afternoon Snow Level
7500'
Tuesday Night Snow Level
7000'

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

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

Date Direction - Speed
Monday Afternoon W 10 - 20
Monday Night W 10 - 20
Tuesday Morning W 5 - 15
Tuesday Afternoon W 5 - 15

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

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
Monday Afternoon W 15 - 25 W 20 - 30 WNW 30 - 40 WNW 45 - 65
Monday Night W 10 - 20 W 20 - 30 WNW 35 - 50 NW 35 - 50
Tuesday Morning WNW 20 - 30 WNW 15 - 25 WNW 40 - 60 NW 25 - 35
Tuesday Afternoon W 25 - 35 W 30 - 40 WNW 40 - 60 WNW 30 - 40
Northwest Cascades
Date Direction - Speed
Monday Afternoon W 15 - 25
Monday Night W 10 - 20
Tuesday Morning WNW 20 - 30
Tuesday Afternoon W 25 - 35
Tuesday Night WNW 30 - 40
Northeast Cascades
Date Direction - Speed
Monday Afternoon W 20 - 30
Monday Night W 20 - 30
Tuesday Morning WNW 15 - 25
Tuesday Afternoon W 30 - 40
Tuesday Night WNW 35 - 50
Central Cascades
Date Direction - Speed
Monday Afternoon WNW 30 - 40
Monday Night WNW 35 - 50
Tuesday Morning WNW 40 - 60
Tuesday Afternoon WNW 40 - 60
Tuesday Night WNW 40 - 60
South Cascades
Date Direction - Speed
Monday Afternoon WNW 45 - 65
Monday Night NW 35 - 50
Tuesday Morning NW 25 - 35
Tuesday Afternoon WNW 30 - 40
Tuesday Night NW 40 - 60

Extended Weather Synopsis for Wednesday through Friday

Showers decrease Wednesday in the northern portions of the Cascades as the shortwave exits the region and the offshore high pressure builds into our region. Significant warming is expected, particularly in the Olympics, South Cascades, and Hood areas.

Wednesday night features mostly dry weather.

On Thursday, an upper shortwave and surface cold front slides down the back side of the offshore ridge and arrives on a NW flow, bringing some initial cooling to the Olympics and west slopes of the Cascades, some precipitation, along with moderate to strong crest-level flow. The ridge re-builds offshore.

Thursday night, the cold front passes through the Cascades, ushering in a much colder air mass along with light post-frontal showers in convergence.

On Friday, light post-frontal showers continue as the offshore ridge, slides eastward and begins to cut them off. Very cold air is in place in the northeast Cascades.

Extended Weather Forecast for Wednesday through Friday

Olympics, Washington Cascades and Mt. Hood Area
Date Weather
Wednesday Mostly cloudy west slopes of the Cascades with very light rain or snow possible in the north Cascades. Mostly cloudy west slopes of the Cascades overnight with little or no rain or snow.
Thursday Increasing light to moderate rain or snow arriving first in the north then central Cascades. Light to occasionally moderate rain and snow weakening as it heads south overnight. Light to moderate post-frontal showers developing along the Cascade west slopes after midnight. Some convergence.

Snow/Freezing Levels

Date Olympics Northwest Cascades Northeast Cascades Central Cascades South Cascades Easterly Flow in Passes
Wednesday Snow Level 7000' - 8000' 4000' - 5000' 4500' - 5500' 5000' - 6500' 8500' - 9500'
Wednesday Night Snow Level 7000' - 8000' 5500' - 6500' 5000' - 6000' 6500' - 7500' 8000' - 9000'
Thursday Snow Level 4500' - 6500' 3000' - 4000' 4000' - 5000' 5000' - 7000' 8000' - 9000'
Thursday Night Snow Level 2500' - 4500' 3000' - 4000' 3000' - 4000' 4000' - 5000' 7000' - 9000'
Olympics
Date Elevation
Wednesday Snow Level
7000' - 8000'
Wednesday Night Snow Level
7000' - 8000'
Thursday Snow Level
4500' - 6500'
Thursday Night Snow Level
2500' - 4500'
Friday Snow Level
1500' - 2500'
Northwest Cascades
Date Elevation
Wednesday Snow Level
4000' - 5000'
Wednesday Night Snow Level
5500' - 6500'
Thursday Snow Level
3000' - 4000'
Thursday Night Snow Level
3000' - 4000'
Friday Snow Level
2000' - 3000'
Northeast Cascades
Date Elevation
Wednesday Snow Level
4500' - 5500'
Wednesday Night Snow Level
5000' - 6000'
Thursday Snow Level
4000' - 5000'
Thursday Night Snow Level
3000' - 4000'
Friday Snow Level
2000' - 3000'
Central Cascades
Date Elevation
Wednesday Snow Level
5000' - 6500'
Wednesday Night Snow Level
6500' - 7500'
Thursday Snow Level
5000' - 7000'
Thursday Night Snow Level
4000' - 5000'
Friday Snow Level
2000' - 3000'
South Cascades
Date Elevation
Wednesday Snow Level
8500' - 9500'
Wednesday Night Snow Level
8000' - 9000'
Thursday Snow Level
8000' - 9000'
Thursday Night Snow Level
7000' - 9000'
Friday 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.