Issued: 1:58 PM PDT Thursday, April 20, 2017
by Dennis D'Amico

Jump to: Weather Forecast I Snow/Freezing Level I Precipitation I Free Winds 5k I Free Winds 9k I Extended Weather

Weather Synopsis for Thursday & Monday

A cool upper level trough is passing through the PNW today. Daytime heating and the cool air mass overhead will help increase shower activity and coverage this afternoon. The air mass is marginally unstable and a rogue thundershower can't be ruled out. Showers should quickly taper off overnight, except for a Puget Sound Convergence Zone expected to form near and north of the Stevens Pass area. Slightly higher accumulations are possible in this area.

The big news is that an entire day of dryness and relative warmth is on tap for Friday. A high amplitude upper level ridge will move over the entire West Coast on Friday. After some morning clouds, freezing levels should rise into the 7000-9000 ft range over the Olympics and Cascades. As has been the case with dry weather forecasts as of late, there are a few caveats. The next approaching frontal system should start to spread some high cloud over the area from the SW in the afternoon. Also, offshore gradients will increase though the Passes.

As the front nears the Washington Coast late Friday night, Pass level offshore winds will become moderate as well as crest level E-SE winds particularly in the southern/central Washington Cascades and Mt. Hood area. Mid and high level clouds will increase Friday night. 

Weather Forecast

Olympics, Washington Cascades near and west of the crest including Stevens, Snoqualmie, and White Passes
Thursday Afternoon

Cloudy with light to occasionally moderate rain and snow showers. Slight chance of a thunderstorm. 

Thursday Night

Light rain and snow showers tapering off and becoming mostly cloudy overnight. 

Friday

Partly cloudy in the morning, becoming mostly sunny by late morning. Warmer. High clouds increasing Friday afternoon. 

Mt. Hood Area
Thursday Afternoon

Cloudy with light to occasionally moderate rain and snow showers. Slight chance of a thunderstorm. 

Thursday Night

Light rain and snow showers tapering off and becoming mostly cloudy overnight. 

Friday

Partly cloudy in the morning, becoming mostly sunny by late morning. Warmer. High clouds increasing Friday afternoon. 

East slopes of the Washington Cascades
Thursday Afternoon

Mostly cloudy with light rain and snow showers, except occasionally moderate near the Cascade crest. Slight chance of a thunderstorm.  Partly cloudy further east.

Thursday Night

Light rain and snow showers tapering off in the evening and becoming partly to mostly clear overnight. 

Friday

Mostly sunny. Warmer. High clouds increasing Friday afternoon. 

Snow/Freezing Level (ft)

Hurricane Ridge Mt. Baker Washington Pass Leavenworth Stevens Pass Snoqualmie Pass Mt. Rainier, Crystal & White Pass Mt. Hood
Thursday Afternoon - Thursday Night Snow Level 5000' 4500' 5000' ' ' 4500' ' 5500'
Friday Morning Freezing Level 4000' 3500' 3500' ' ' 3000' ' 4000'
Hurricane Ridge Elevation
Thursday Afternoon - Thursday Night Snow Level
5000'
Friday Morning Freezing Level
4000'
Friday Afternoon - Friday Night Freezing Level
7500'
(Easterly Flow *)
Mt. Baker Elevation
Thursday Afternoon - Thursday Night Snow Level
4500'
Friday Morning Freezing Level
3500'
Friday Afternoon - Friday Night Freezing Level
7500'
(Easterly Flow *)
Washington Pass Elevation
Thursday Afternoon - Thursday Night Snow Level
5000'
Friday Morning Freezing Level
3500'
Friday Afternoon - Friday Night Freezing Level
7000'
(Easterly Flow *)
Leavenworth Elevation
Thursday Afternoon - Thursday Night Snow Level
'
Friday Morning Freezing Level
'
Friday Afternoon - Friday Night Freezing Level
'
(Easterly Flow *)
Stevens Pass Elevation
Thursday Afternoon - Thursday Night Snow Level
'
Friday Morning Freezing Level
'
Friday Afternoon - Friday Night Freezing Level
'
(Easterly Flow *)
Snoqualmie Pass Elevation
Thursday Afternoon - Thursday Night Snow Level
4500'
Friday Morning Freezing Level
3000'
Friday Afternoon - Friday Night Freezing Level
7500'
(Easterly Flow *)
Mt. Rainier & Crystal Elevation
Thursday Afternoon - Thursday Night Snow Level
'
Friday Morning Freezing Level
'
Friday Afternoon - Friday Night Freezing Level
'
(Easterly Flow *)
Mt. Hood Elevation
Thursday Afternoon - Thursday Night Snow Level
5500'
Friday Morning Freezing Level
4000'
Friday Afternoon - Friday Night Freezing Level
8500'
(Easterly Flow *)

* Easterly flow in the Cascade Passes can cause locally lower Snow or Freezing levels than areas further west.
Freezing Level is when no precipitation is forecast.

Precipitation Forecast

Monday Monday
Hurricane Ridge LT 0.25 LT 0.10
Mt Baker Ski Area 0.25 - 0.50 LT 0.10
Washington Pass LT 0.10 LT 0.10
Stevens Pass 0.25 - 0.50 LT 0.10
Snoqualmie Pass 0.25 - 0.50 LT 0.10
Mission Ridge LT 0.10 LT 0.10
Crystal Mt LT 0.25 LT 0.10
Paradise 0 - 0.50 LT 0.10
White Pass LT 0.25 LT 0.10
Mt Hood Meadows LT 0.25 LT 0.10
0.25 - 0.50 LT 0.10

Free Winds at 5000' (mph)

Hurricane Ridge Mt. Baker Stevens to Snoqualmie Pass Mt. Rainier Mt. Hood
Thursday Afternoon W 0 - 10 WSW 0 - 10 WSW 5 - 15 --- - W 15 - 25
Thursday Night - Friday Morning E 0 - 10 VAR 0 - 10 W 0 - 10 --- - W 5 - 15
Friday Afternoon SE 5 - 15 E 5 - 15 ESE 10 - 20 --- - ESE 15 - 25
Hurricane Ridge Elevation
Thursday Afternoon W 0 - 10
Thursday Night - Friday Morning E 0 - 10
Friday Afternoon SE 5 - 15
Friday Night SE 10 - 20
Mt. Baker Elevation
Thursday Afternoon WSW 0 - 10
Thursday Night - Friday Morning VAR 0 - 10
Friday Afternoon E 5 - 15
Friday Night E 5 - 15
Stevens and Snoqualmie Pass Elevation
Thursday Afternoon WSW 5 - 15
Thursday Night - Friday Morning W 0 - 10
Friday Afternoon ESE 10 - 20
Friday Night ESE 20 - 35
Mt. Rainier Elevation
Thursday Afternoon --- -
Thursday Night - Friday Morning --- -
Friday Afternoon --- -
Friday Night --- -
Mt. Hood Elevation
Thursday Afternoon W 15 - 25
Thursday Night - Friday Morning W 5 - 15
Friday Afternoon ESE 15 - 25
Friday Night SE 15 - 25
Hurricane Ridge Direction - Speed
Thursday Afternoon W 0 - 10
Thursday Night - Friday Morning E 0 - 10
Friday Afternoon SE 5 - 15
Friday Night SE 10 - 20
Mt. Baker Direction - Speed
Thursday Afternoon WSW 0 - 10
Thursday Night - Friday Morning VAR 0 - 10
Friday Afternoon E 5 - 15
Friday Night E 5 - 15
Stevens and Snoqualmie Pass Direction - Speed
Thursday Afternoon WSW 5 - 15
Thursday Night - Friday Morning W 0 - 10
Friday Afternoon ESE 10 - 20
Friday Night ESE 20 - 35
Mt. Rainier Direction - Speed
Thursday Afternoon --- -
Thursday Night - Friday Morning --- -
Friday Afternoon --- -
Friday Night --- -
Mt. Hood Direction - Speed
Thursday Afternoon W 15 - 25
Thursday Night - Friday Morning W 5 - 15
Friday Afternoon ESE 15 - 25
Friday Night SE 15 - 25

Directions above indicate the direction the wind blows from on the 16-point cardinal scale. These winds 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' (mph)

Mt. Baker Washington Pass Stevens to Snoqualmie Pass Mt. Rainier Mt. Hood
Thursday Afternoon W 10 - 20 WNW 15 - 25 W 15 - 30 --- - W 15 - 25
Thursday Night - Friday Morning N 5 - 15 N 10 - 20 N 5 - 15 --- - NW 0 - 10
Friday Afternoon S 10 - 20 SE 5 - 15 SE 20 - 30 --- - S 10 - 20
Mt. Baker Direction - Speed
Thursday Afternoon W 10 - 20
Thursday Night - Friday Morning N 5 - 15
Friday Afternoon S 10 - 20
Friday Night S 10 - 20
Washington Pass Direction - Speed
Thursday Afternoon WNW 15 - 25
Thursday Night - Friday Morning N 10 - 20
Friday Afternoon SE 5 - 15
Friday Night S 15 - 25
Stevens and Snoqualmie Pass Direction - Speed
Thursday Afternoon W 15 - 30
Thursday Night - Friday Morning N 5 - 15
Friday Afternoon SE 20 - 30
Friday Night SSE 20 - 35
Mt. Rainier Direction - Speed
Thursday Afternoon --- -
Thursday Night - Friday Morning --- -
Friday Afternoon --- -
Friday Night --- -
Mt. Hood Direction - Speed
Thursday Afternoon W 15 - 25
Thursday Night - Friday Morning NW 0 - 10
Friday Afternoon S 10 - 20
Friday Night S 15 - 30

Extended Weather Synopsis for Monday night through Monday

The slow moving front should lift northeastward over the area on Saturday, with light rain and snow becoming showers in the afternoon. Locally moderate showers are most likely for the west slopes of the Cascades and Olympics, especially the Mt. Baker area Saturday night.  The trailing longwave upper level trough should pass through the area on Sunday, with showers once again increasing in the afternoon. The moisture profile looks deeper on Sunday, so expect a cloudier and cooler day especially along the west slopes of the Cascades. 

A rather impressive looking low pressure system for April is forecast to move into western Washington/southern British Columbia on Monday. The exact track will make a difference to how much rain and snow we receive, but a broad brush forecast of wetter and cooler than normal looks accurate for all areas on Monday. 

Extended Weather

Olympics, Washington Cascades and Mt. Hood area
Saturday - Saturday Evening

Periods of light rain and snow becoming light rain and snow showers, occasionally moderate along the west slopes of the Cascades and Olympics. More sunshine along the east slopes of the central-east and southeast Cascades. 

Saturday Night - Sunday Morning

Mostly cloudy with isolated rain and snow showers. 

Sunday Afternoon

Cloudy with light rain and snow showers, occasionally moderate west slopes of the Cascades, Olympics and Mt. Hood. 

Sunday Night

Mostly cloudy with scattered light rain and snow showers. 

Monday

Increasing light to moderate rain and snow. 

Extended Snow/Freezing Levels

Mt. Baker Snoqualmie Pass Mt. Hood Easterly Flow *
Saturday Snow Level 5500' - 6500' 5500' - 6500' 6000' - 7000'
Saturday Night - Sunday Snow Level 4500' - 5500' 4500' - 5500' 4500' - 5500'
Mt. Baker Elevation
Saturday Snow Level
5500' - 6500'
Saturday Night - Sunday Snow Level
4500' - 5500'
Sunday Night - Monday Snow Level
4000' - 5000'
Snoqualmie Pass Elevation
Saturday Snow Level
5500' - 6500'
Saturday Night - Sunday Snow Level
4500' - 5500'
Sunday Night - Monday Snow Level
4000' - 5000'
Mt. Hood Elevation
Saturday Snow Level
6000' - 7000'
Saturday Night - Sunday Snow Level
4500' - 5500'
Sunday Night - Monday Snow Level
4000' - 5000'

* Easterly flow in the Cascade Passes can cause locally lower Snow or Freezing levels than areas further west.
Freezing Level is when no precipitation is forecast.

Jump to: Weather Forecast I Snow/Freezing Level I Precipitation I Free Winds 5k I Free Winds 9k I Extended Weather

Previous forecast from Apr 15, 2017

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.

Spring Schedule: The NWAC issued daily mountain weather and avalanche forecasts through Saturday, April 15th. Mountain weather and avalanche forecasts will be issued during the spring transition April 20-22nd and April 27-29th. Weekend outlooks will be issued Thursdays, May 4th, 11th, 18th and 25th.