menu

Mountain Weather Forecast

Issued: 6:04 PM PST Wednesday, February 7, 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 Wednesday & Thursday

On Wednesday, the Pacific Northwest continues to sit between a robust and relatively stationary high pressure off the northern coast of California and a deep low over Hudson's Bay. The jetstream lies to our north, taking today's storm track and precipitation on a higher-latitude trajectory than previously expected. The resulting weather has been warmer than anticipated for Wednesday, with relatively drier weather. Winds have been and will continue to be moderate to strong on the east slopes of the Cascades at higher elevation and downslope winds to the east of the Cascades have scoured out the cold pool that normally resides there. Mazama saw an 18F jump in temperature in just one hour this morning due to a wind shift from E to W and temperatures are now in the mid-50's. Winds below crest-level have been light to moderate.

To the west of the Cascade crest the atmosphere has been very stable on Wednesday morning, meaning that the temperature doesn't decrease significantly with height as you normally expect. Temperatures are in the low-to-mid 30's at most NWAC stations, including Camp Muir!

Light precipitation is beginning to re-develop in the Northwest Cascades this afternoon with light amounts expected. Some locations in the central and north Cascades (west slopes) have also experienced freezing rain above 5000 feet or drizzle. 

As a system approaches from the W-NW tonight, W-SW winds will increase to the moderate-to-strong range by morning at crest level and snow levels will begin lowing slightly as the jetstream drops southward, pushing the ridge back south. In some cases east of the Cascade crest, winds will be very strong tonight.

On Thurday, the reasonably strong, but relatively moisture-starved surface cold front associated with a short-wave trough will cross the Pacific Northwest, arriving in the Olympics in the early morning, then the NW Cascades around 10 AM and reaching Mt. Hood during the evening hours.

Snow levels will drop significantly behind the front with rain changing back to snow at many mid-elevation locations between 1-4PM at the Mt. Baker base and between 4 and 7 PM for Stevens Pass and Crystal Base, with a changeover at Snoqualmie pass level likely after 7 PM. Most precipitation will be with moderate post-frontal showers behind the cold front and a potentially strong convergence zone that is likely to set up in the Stevens Pass vicinity during the afternoon and early evening hours.

Some lighter convergence will focus lingering snowfall in the Snoqualmie Pass vicinity on Thursday night.

Weather forecast for Wednesday & Thursday

Olympics
Date Weather
Wednesday Partly cloudy with filtered sunlight. Moderate ridgetop westerly winds.
Wednesday Night Fair with partly cloudy skies. Moderate ridgetop W-SW winds increasing to strong at times.
Thursday Mostly cloudy, becoming partly cloudy in the afternoon. Strong ridgetop W-SW winds.
Becoming mostly clear. Moderate ridgetop westerly winds.
Washington Cascades near and west of the Crest including Stevens, Snoqualmie and White Passes
Date Weather
Wednesday Cloudy central to north Cascades with some light rain or drizzle. Sunny south Cascades. Moderate crest-level westerly winds.
Wednesday Night Mostly high clouds. Crest-level winds becoming moderate to strong.
Thursday Increasing light or moderate rain and snow showers with lowering snow levels, particularly in the afternoon. Heaviest rain/snow in convergence near Stevens Pass in the afternoon. Expect filtered sunlight further south in the morning with low clouds moving in during the afternoon. Moderate to strong W-SW crest-level winds.
Mostly cloudy with westerly winds decreasing.
East Slopes of the Washington Cascades
Date Weather
Wednesday Cloudy central to north Cascades near the crest with some light rain or drizzle possible. Sunny south Cascades and east of the crest with warm temperatures replacing the typical mid-winter cold pool. Moderate crest-level westerly winds. Moderate to strong crest-level westerly winds.
Wednesday Night Mostly high clouds. Crest-level winds becoming moderate to strong.
Thursday Light rain and snow showers developing near the Cascade crest in the central and north Cascades. Filtered sunlight elsewhere. Moderate to strong W-SW winds.
Becoming partly to mostly clear with westerly winds decreasing.
Mt. Hood
Date Weather
Wednesday Low clouds dissipating early, then increasing high clouds.
Wednesday Night High clouds.
Thursday Increasing clouds in the afternoon.
Mostly cloudy.

Snow Level/Freezing Level in feet

Date Olympics Northwest Cascades Northeast Cascades Central Cascades South Cascades Easterly Flow in Passes
Wednesday Afternoon Snow Level 8000' 6500' 6500' 7500' 9500'
Wednesday Night Snow Level 6500' 5000' 5500' 6500' 9000'
Thursday Morning Snow Level 5000' 4000' 4000' 4500' 8500'
Thursday Afternoon Snow Level 3500' 4000' 4500' 4000' 8500'
Olympics
Date Elevation
Wednesday Afternoon Snow Level
8000'
Wednesday Night Snow Level
6500'
Thursday Morning Snow Level
5000'
Thursday Afternoon Snow Level
3500'
Thursday Night Snow Level
2500'
Northwest Cascades
Date Elevation
Wednesday Afternoon Snow Level
6500'
Wednesday Night Snow Level
5000'
Thursday Morning Snow Level
4000'
Thursday Afternoon Snow Level
4000'
Thursday Night Snow Level
2500'
Northeast Cascades
Date Elevation
Wednesday Afternoon Snow Level
6500'
Wednesday Night Snow Level
5500'
Thursday Morning Snow Level
4000'
Thursday Afternoon Snow Level
4500'
Thursday Night Snow Level
2500'
Central Cascades
Date Elevation
Wednesday Afternoon Snow Level
7500'
Wednesday Night Snow Level
6500'
Thursday Morning Snow Level
4500'
Thursday Afternoon Snow Level
4000'
Thursday Night Snow Level
2500'
South Cascades
Date Elevation
Wednesday Afternoon Snow Level
9500'
Wednesday Night Snow Level
9000'
Thursday Morning Snow Level
8500'
Thursday Afternoon Snow Level
8500'
Thursday Night Snow Level
4500'

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 Thu Fri
Hurricane Ridge 0 0
Mt Baker Ski Area .25 - .50 .25 - .50
Washington Pass .10 .25 - .50
Stevens Pass lt .10 .75 - 1.00
Snoqualmie Pass lt .10 .25 - .50
Mission Ridge 0 0
Crystal Mt lt .10 0
Paradise lt .25 lt .10
White Pass 0 lt .10
Mt Hood Meadows 0 0

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

Date Direction - Speed
Wednesday Afternoon W 10 - 20
Wednesday Night W 20 - 30
Thursday Morning W 20 - 30
Thursday Afternoon W 15 - 25

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
Wednesday Afternoon W 20 - 30 W 15 - 25 W 10 - 20 W 10 - 20
Wednesday Night WSW 25 - 40 WSW 20 - 35 WSW 30 - 40 WSW 30 - 40
Thursday Morning WSW 25 - 35 WSW 20 - 30 WSW 30 - 40 WSW 30 - 40
Thursday Afternoon WSW 20 - 30 WSW 10 - 20 WSW 25 - 35 W 30 - 40
Olympics
Date Elevation
Wednesday Afternoon W 20 - 30
Wednesday Night WSW 25 - 40
Thursday Morning WSW 25 - 35
Thursday Afternoon WSW 20 - 30
Thursday Night WSW 5 - 15
Northwest Cascades
Date Elevation
Wednesday Afternoon W 15 - 25
Wednesday Night WSW 20 - 35
Thursday Morning WSW 20 - 30
Thursday Afternoon WSW 10 - 20
Thursday Night SW 5 - 15
Central Cascades
Date Elevation
Wednesday Afternoon W 10 - 20
Wednesday Night WSW 30 - 40
Thursday Morning WSW 30 - 40
Thursday Afternoon WSW 25 - 35
Thursday Night W 5 - 15
South Cascades
Date Elevation
Wednesday Afternoon W 10 - 20
Wednesday Night WSW 30 - 40
Thursday Morning WSW 30 - 40
Thursday Afternoon W 30 - 40
Thursday Night W 20 - 35
Olympics
Date Direction - Speed
Wednesday Afternoon W 20 - 30
Wednesday Night WSW 25 - 40
Thursday Morning WSW 25 - 35
Thursday Afternoon WSW 20 - 30
Thursday Night WSW 5 - 15
Northwest Cascades
Date Direction - Speed
Wednesday Afternoon W 15 - 25
Wednesday Night WSW 20 - 35
Thursday Morning WSW 20 - 30
Thursday Afternoon WSW 10 - 20
Thursday Night SW 5 - 15
Central Cascades
Date Direction - Speed
Wednesday Afternoon W 10 - 20
Wednesday Night WSW 30 - 40
Thursday Morning WSW 30 - 40
Thursday Afternoon WSW 25 - 35
Thursday Night W 5 - 15
South Cascades
Date Direction - Speed
Wednesday Afternoon W 10 - 20
Wednesday Night WSW 30 - 40
Thursday Morning WSW 30 - 40
Thursday Afternoon W 30 - 40
Thursday Night W 20 - 35

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
Wednesday Afternoon W 45 - 65 W 50 - 70 W 50 - 70 WNW 25 - 35
Wednesday Night WSW 50 - 70 WSW 60 - 80 WSW 60 - 80 W 50 - 70
Thursday Morning WSW 35 - 45 WSW 50 - 70 W 40 - 60 W 60 - 80
Thursday Afternoon W 25 - 35 WSW 30 - 40 W 40 - 60 W 55 - 75
Northwest Cascades
Date Direction - Speed
Wednesday Afternoon W 45 - 65
Wednesday Night WSW 50 - 70
Thursday Morning WSW 35 - 45
Thursday Afternoon W 25 - 35
Thursday Night W 10 - 20
Northeast Cascades
Date Direction - Speed
Wednesday Afternoon W 50 - 70
Wednesday Night WSW 60 - 80
Thursday Morning WSW 50 - 70
Thursday Afternoon WSW 30 - 40
Thursday Night W 15 - 25
Central Cascades
Date Direction - Speed
Wednesday Afternoon W 50 - 70
Wednesday Night WSW 60 - 80
Thursday Morning W 40 - 60
Thursday Afternoon W 40 - 60
Thursday Night WNW 35 - 55
South Cascades
Date Direction - Speed
Wednesday Afternoon WNW 25 - 35
Wednesday Night W 50 - 70
Thursday Morning W 60 - 80
Thursday Afternoon W 55 - 75
Thursday Night NW 45 - 65

Extended Weather Synopsis for Friday through Sunday

A moderate jet will remain over the area on Friday, with some light snow showers on a light W-NW flow along the west slopes of the Cascades.

Late Friday into Friday night, an upper trough to the NE will retrograde to the west, spawning a back-door coldfront that pushes south and may bring a few snow showers to the Mt. Hood area on Friday night. Over Washington, expect clearing skies and light winds with low freezing levels.

Saturday, should feature a brief period of relatively cool high pressure with clear skies, rebounding freezing levels, and light winds as a northward tongue of our trusty offshore high pressure slides east to replace the southward-moving shortwave trough. 

The high pressure should hold through Saturday night with clear skies and low freezing levels.

Models agree that a storm will impact the northwest at some point on Saturday on a NW flow coming down the back-side of the high pressure ridge, but the models disagree regarding the track. Some models take the storm offshore into central Oregon, cutting off the potential for much moisture getting into our mountains. Other tracks take it directly into Washington during the daylight hours on Sunday. At this time, the upper and surface low look to bring another round of colder air and the potential for snow to lower elevations.

Extended Weather Forecast for Friday through Sunday

Olympics, Washington Cascades and Mt. Hood Area
Date Weather
Friday Decreasing light snow showers, heaviest in weak convergence, in the Washington Cascades west of the crest. Clearing Saturday night, except snow showers lingering over northern Oregon.
Saturday Clear and fair weather Saturday and Saturday night.

Snow/Freezing Levels

Date Olympics Northwest Cascades Northeast Cascades Central Cascades South Cascades Easterly Flow in Passes
Friday Snow Level None' - None' None' - None' None' - None' None' - None' None' - None'
Friday Night Snow Level None' - None' None' - None' None' - None' None' - None' None' - None'
Saturday Snow Level None' - None' None' - None' None' - None' None' - None' None' - None'
Saturday Night Snow Level None' - None' None' - None' None' - None' None' - None' None' - None'
Olympics
Date Elevation
Friday Snow Level
None' - None'
Friday Night Snow Level
None' - None'
Saturday Snow Level
None' - None'
Saturday Night Snow Level
None' - None'
Sunday Snow Level
None' - None'
Northwest Cascades
Date Elevation
Friday Snow Level
None' - None'
Friday Night Snow Level
None' - None'
Saturday Snow Level
None' - None'
Saturday Night Snow Level
None' - None'
Sunday Snow Level
None' - None'
Northeast Cascades
Date Elevation
Friday Snow Level
None' - None'
Friday Night Snow Level
None' - None'
Saturday Snow Level
None' - None'
Saturday Night Snow Level
None' - None'
Sunday Snow Level
None' - None'
Central Cascades
Date Elevation
Friday Snow Level
None' - None'
Friday Night Snow Level
None' - None'
Saturday Snow Level
None' - None'
Saturday Night Snow Level
None' - None'
Sunday Snow Level
None' - None'
South Cascades
Date Elevation
Friday Snow Level
None' - None'
Friday Night Snow Level
None' - None'
Saturday Snow Level
None' - None'
Saturday Night Snow Level
None' - None'
Sunday Snow Level
None' - None'

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.