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Mountain Weather Forecast

Issued: 8:14 AM PST Friday, April 21, 2017
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 Friday & Saturday

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 West Coast today. After a relatively cool start this morning with most mountain sites in the mid to upper 20s, freezing levels should rise into the 7500-9000 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 creating locally breezy conditions this afternoon and tonight. Crest level E-SE winds particularly in the southern/central Washington Cascades and the Mt. Hood area will increase overnight as the next Pacific frontal system approaches.

Mid and high level clouds will increase Friday night in advance of the front, but precipitation should hold off until Saturday morning. Rain and snow will lift northeast over the area during the day on Saturday, followed by post-frontal showers late Saturday afternoon. Showers should taper off Saturday night.  

Weather forecast for Friday & Saturday

Olympics
Date Weather
Friday

Mostly sunny. Warmer. Increasing high clouds late in the afternoon. 

Friday Night

Becoming partly to mostly cloudy.

Saturday

Light to occasionally moderate rain and snow developing mid-morning and becoming light rain and snow showers in the afternoon. 

Mostly cloudy with light rain and snow showers tapering down overnight. 

Washington Cascades near and west of the crest including Stevens, Snoqualmie, and White Passes
Date Weather
Friday

Mostly sunny. Warmer. Locally breezy E-SE winds. Increasing high clouds late in the afternoon. 

Friday Night

Becoming partly to mostly cloudy. Locally breezy E-SE winds. 

Saturday

Light rain and snow developing mid-morning and becoming light rain and snow showers in the afternoon, occasionally moderate in the Mt. Baker area. A few sunbreaks in the southwest Cascades in the afternoon. 

Mostly cloudy with light rain and snow showers tapering down overnight, except occasionally moderate Mt. Baker area. 

East slopes of the Washington Cascades
Date Weather
Friday

Mostly sunny. Warmer. Increasing high clouds late in the afternoon. 

Friday Night

Becoming partly cloudy. 

Saturday

Cloudy with light rain and snow developing mid-morning, then becoming mostly cloudy with scattered light rain and snow showers in the afternoon.

 

Partly to mostly cloudy with isolated light rain and snow showers ending in the evening.  

Mt. Hood Area
Date Weather
Friday

Mostly sunny. Warmer. Locally breezy E-SE winds. Increasing high clouds late in the afternoon. 

Friday Night

Becoming partly to mostly cloudy. Locally breezy E-SE winds. 

Saturday

Very light rain and snow developing in the morning and becoming mostly cloudy with scattered light rain and snow showers in the afternoon. 

Mostly cloudy with isolated light rain and snow showers in the evening ending overnight and becoming partly cloudy. 

Snow Level/Freezing Level in feet

Date Olympics Northwest Cascades Northeast Cascades Central Cascades South Cascades Easterly Flow in Passes
Friday Morning Freezing Level 4500' 3500' 3500' 3500' 4500' *
Friday Afternoon - Friday Night Freezing Level 7500' 7500' 7000' 7500' 8500' *
Saturday Snow Level 5500' 5500' 5500' 5500' 6000'
Olympics
Date Elevation
Friday Morning Freezing Level
4500'
Easterly Flow*
Friday Afternoon - Friday Night Freezing Level
7500'
Easterly Flow*
Saturday Snow Level
5500'
Saturday Night Snow Level
4000'
Northwest Cascades
Date Elevation
Friday Morning Freezing Level
3500'
Easterly Flow*
Friday Afternoon - Friday Night Freezing Level
7500'
Easterly Flow*
Saturday Snow Level
5500'
Saturday Night Snow Level
4000'
Northeast Cascades
Date Elevation
Friday Morning Freezing Level
3500'
Easterly Flow*
Friday Afternoon - Friday Night Freezing Level
7000'
Easterly Flow*
Saturday Snow Level
5500'
Saturday Night Snow Level
4000'
Central Cascades
Date Elevation
Friday Morning Freezing Level
3500'
Easterly Flow*
Friday Afternoon - Friday Night Freezing Level
7500'
Easterly Flow*
Saturday Snow Level
5500'
Saturday Night Snow Level
4000'
South Cascades
Date Elevation
Friday Morning Freezing Level
4500'
Easterly Flow*
Friday Afternoon - Friday Night Freezing Level
8500'
Easterly Flow*
Saturday Snow Level
6000'
Saturday 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 Sat Sun
Hurricane Ridge 0 .25
Mt Baker Ski Area 0 .50
Washington Pass 0 lt .25
Stevens Pass 0 .25
Snoqualmie Pass 0 .25
Mission Ridge 0 lt .10
Crystal Mt 0 lt .25
Paradise 0 .25
White Pass 0 lt .25
Mt Hood Meadows 0 lt .10

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

Date Direction - Speed
Friday Morning VAR 0 - 10
Friday Afternoon E 10 - 20
Friday Night - Saturday Morning E 15 - 30
Saturday Afternoon W 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
Friday Morning E 5 - 15 VAR 0 - 10 E 0 - 10 VAR 0 - 10
Friday Afternoon SE 10 - 20 E 5 - 15 ESE 15 - 25 E 15 - 25
Friday Night - Saturday Morning SE 10 - 20 E 5 - 15 ESE 20 - 35 ESE 15 - 30
Saturday Afternoon SSW 15 - 25 S 15 - 25 SW 10 - 20 WSW 10 - 20
Olympics
Date Elevation
Friday Morning E 5 - 15
Friday Afternoon SE 10 - 20
Friday Night - Saturday Morning SE 10 - 20
Saturday Afternoon SSW 15 - 25
Saturday Night SW 0 - 10
Northwest Cascades
Date Elevation
Friday Morning VAR 0 - 10
Friday Afternoon E 5 - 15
Friday Night - Saturday Morning E 5 - 15
Saturday Afternoon S 15 - 25
Saturday Night S 5 - 15
Central Cascades
Date Elevation
Friday Morning E 0 - 10
Friday Afternoon ESE 15 - 25
Friday Night - Saturday Morning ESE 20 - 35
Saturday Afternoon SW 10 - 20
Saturday Night SW 0 - 10
South Cascades
Date Elevation
Friday Morning VAR 0 - 10
Friday Afternoon E 15 - 25
Friday Night - Saturday Morning ESE 15 - 30
Saturday Afternoon WSW 10 - 20
Saturday Night WSW 5 - 15
Olympics
Date Direction - Speed
Friday Morning E 5 - 15
Friday Afternoon SE 10 - 20
Friday Night - Saturday Morning SE 10 - 20
Saturday Afternoon SSW 15 - 25
Saturday Night SW 0 - 10
Northwest Cascades
Date Direction - Speed
Friday Morning VAR 0 - 10
Friday Afternoon E 5 - 15
Friday Night - Saturday Morning E 5 - 15
Saturday Afternoon S 15 - 25
Saturday Night S 5 - 15
Central Cascades
Date Direction - Speed
Friday Morning E 0 - 10
Friday Afternoon ESE 15 - 25
Friday Night - Saturday Morning ESE 20 - 35
Saturday Afternoon SW 10 - 20
Saturday Night SW 0 - 10
South Cascades
Date Direction - Speed
Friday Morning VAR 0 - 10
Friday Afternoon E 15 - 25
Friday Night - Saturday Morning ESE 15 - 30
Saturday Afternoon WSW 10 - 20
Saturday Night WSW 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
Friday Morning N 5 - 15 N 5 - 15 E 0 - 10 NW 0 - 10
Friday Afternoon SE 5 - 15 SE 5 - 15 SE 20 - 30 S 10 - 20
Friday Night - Saturday Morning S 10 - 20 S 15 - 25 S 20 - 30 S 15 - 25
Saturday Afternoon SW 25 - 35 SW 15 - 25 SW 20 - 30 SW 25 - 35
Northwest Cascades
Date Direction - Speed
Friday Morning N 5 - 15
Friday Afternoon SE 5 - 15
Friday Night - Saturday Morning S 10 - 20
Saturday Afternoon SW 25 - 35
Saturday Night SW 5 - 15
Northeast Cascades
Date Direction - Speed
Friday Morning N 5 - 15
Friday Afternoon SE 5 - 15
Friday Night - Saturday Morning S 15 - 25
Saturday Afternoon SW 15 - 25
Saturday Night WSW 5 - 15
Central Cascades
Date Direction - Speed
Friday Morning E 0 - 10
Friday Afternoon SE 20 - 30
Friday Night - Saturday Morning S 20 - 30
Saturday Afternoon SW 20 - 30
Saturday Night WSW 10 - 20
South Cascades
Date Direction - Speed
Friday Morning NW 0 - 10
Friday Afternoon S 10 - 20
Friday Night - Saturday Morning S 15 - 25
Saturday Afternoon SW 25 - 35
Saturday Night SW 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.

The Extended Mountain Weather Forecast (Days 3-5) will be included with the afternoon forecast issuance around 1:30 PM.