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Mountain Weather Forecast

Issued: 4:02 PM PST Saturday, April 14, 2018
by Robert Hahn

April 14th marks the last regularly scheduled mountain weather forecast issuance for the 2017-2018 season. 

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

A cool upper trough will drop SE from the Gulf of Alaska on Saturday, while out ahead of it, a frontal wave is currently moving NE along a stalled frontal boundary with copious moisture heading for the Washington Cascades and Olympics as of mid-afternoon on Saturday. Rain and snow previously focused on a more narrow band over the central Cascades is expected to fill in throughout the Washington Cascades, with significant precipitation spilling over to the east slopes of the Cascades. Mild temperatures will keep snow levels above pass level and temperatures are particularly warm along the east slopes of the Cascades associated with subsidence warm. Mazama reached 61F on Saturday afternoon.

The front will push south and east late Saturday night, shifting the precipitation south to the Mt. Hood area, but it will not bring much more than diurnal cooling.

As the upper trough moves into our offshore waters on Sunday, a new surface feature will slide north, extending light to moderate rain and snow showers throughout the Cascades. Expect some convection with cool air aloft as the upper level trough continues moving into the region. 

Sunday night the upper low moves near the Washington/Oregon coastline, bringing cooling. The northward exit of the surface feature, will allow moderate Westerly flow to develop over our region.

 

Weather forecast for Saturday & Sunday

Olympics
Date Weather
Saturday Light rain or snow.
Saturday Night Light rain or snow during the evening with mostly high clouds after midnight.
Sunday Filtered sunlight with cumulus clouds building during the afternoon and a chance of a rain or snow shower.
A chance of light rain or snow showers. Cooler.
Washington Cascades near and west of the Crest including Stevens, Snoqualmie and White Passes
Date Weather
Saturday Increasing moderate to heavy rain and snow spreading throughout the Cascades.
Saturday Night Moderate to occasionally heavy rain and snow during the evening hours. Becoming light rain and snow showers after midnight.
Sunday Mostly cloudy with high clouds above with light rain and snow spreading from south to north during the afternoon. Heaviest precipitation in the south. Expect some convective precipitation with locally heavy amounts in the afternoon.
Light rain and snow showers with locally heavier amounts.
East Slopes of the Washington Cascades
Date Weather
Saturday Decreasing light to moderate rain and snow central and south Cascades in the morning, with mostly light rain or snow north. Increasing moderate rain and snow spreading throughout the Cascades in the afternoon.
Saturday Night Moderate rain and snow during the evening hours. Becoming light rain and snow showers mainly near the Cascade crest after midnight.
Sunday Mostly cloudy with high clouds above with light rain and snow spreading from south to north during the afternoon. Heaviest precipitation in the south. Expect some convective precipitation with locally heavy amounts in the afternoon.
Light rain and snow showers with locally heavier amounts.
Mt. Hood
Date Weather
Saturday Mostly cloudy with a chance of a light rain or snow shower, particularly late in the day.
Saturday Night Light rain and snow.
Sunday Light to moderate rain and snow developing. Convection likely during the afternoon.
Light to occasionally moderate rain and snow showers.

Snow Level/Freezing Level in feet

Date Olympics Northwest Cascades Northeast Cascades Central Cascades South Cascades Easterly Flow in Passes
Saturday Afternoon Snow Level 3500' 4000' 5000' 5000' 5500'
Saturday Night Snow Level 2500' 3000' 3500' 4000' 4500'
Sunday Morning Snow Level 2500' 3500' 4500' 4000' 5000'
Sunday Afternoon Snow Level 3000' 4000' 5000' 4500' 4500'
Olympics
Date Elevation
Saturday Afternoon Snow Level
3500'
Saturday Night Snow Level
2500'
Sunday Morning Snow Level
2500'
Sunday Afternoon Snow Level
3000'
Sunday Night Snow Level
3000'
Northwest Cascades
Date Elevation
Saturday Afternoon Snow Level
4000'
Saturday Night Snow Level
3000'
Sunday Morning Snow Level
3500'
Sunday Afternoon Snow Level
4000'
Sunday Night Snow Level
3000'
Northeast Cascades
Date Elevation
Saturday Afternoon Snow Level
5000'
Saturday Night Snow Level
3500'
Sunday Morning Snow Level
4500'
Sunday Afternoon Snow Level
5000'
Sunday Night Snow Level
4000'
Central Cascades
Date Elevation
Saturday Afternoon Snow Level
5000'
Saturday Night Snow Level
4000'
Sunday Morning Snow Level
4000'
Sunday Afternoon Snow Level
4500'
Sunday Night Snow Level
3000'
South Cascades
Date Elevation
Saturday Afternoon Snow Level
5500'
Saturday Night Snow Level
4500'
Sunday Morning Snow Level
5000'
Sunday Afternoon Snow Level
4500'
Sunday Night Snow Level
2500'

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 .25 - .50 .25
Mt Baker Ski Area 1.00 - 1.50 .50
Washington Pass .50 - .70 .50 - .75
Stevens Pass 1.00 .50
Snoqualmie Pass 1.00 - 1.50 .50 - .75
Mission Ridge lt .25 .25 - .50
Crystal Mt .50 - .75 .50
Paradise 1.50 .75
White Pass .25 - .50 .50
Mt Hood Meadows .25 .75

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

Date Direction - Speed
Saturday Afternoon W 10 - 20
Saturday Night VAR 0 - 10
Sunday Morning E 5 - 15
Sunday Afternoon E 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
Saturday Afternoon SW 10 - 20 S 5 - 15 S 10 - 20 SW 20 - 30
Saturday Night WSW 0 - 10 S 0 - 10 W 5 - 15 WSW 15 - 25
Sunday Morning E 5 - 15 E 5 - 15 E 5 - 15 S 10 - 20
Sunday Afternoon N 5 - 15 N 5 - 15 VAR 0 - 10 W 5 - 15
Olympics
Date Elevation
Saturday Afternoon SW 10 - 20
Saturday Night WSW 0 - 10
Sunday Morning E 5 - 15
Sunday Afternoon N 5 - 15
Sunday Night W 10 - 20
Northwest Cascades
Date Elevation
Saturday Afternoon S 5 - 15
Saturday Night S 0 - 10
Sunday Morning E 5 - 15
Sunday Afternoon N 5 - 15
Sunday Night WSW 5 - 15
Central Cascades
Date Elevation
Saturday Afternoon S 10 - 20
Saturday Night W 5 - 15
Sunday Morning E 5 - 15
Sunday Afternoon VAR 0 - 10
Sunday Night W 15 - 25
South Cascades
Date Elevation
Saturday Afternoon SW 20 - 30
Saturday Night WSW 15 - 25
Sunday Morning S 10 - 20
Sunday Afternoon W 5 - 15
Sunday Night W 20 - 30
Olympics
Date Direction - Speed
Saturday Afternoon SW 10 - 20
Saturday Night WSW 0 - 10
Sunday Morning E 5 - 15
Sunday Afternoon N 5 - 15
Sunday Night W 10 - 20
Northwest Cascades
Date Direction - Speed
Saturday Afternoon S 5 - 15
Saturday Night S 0 - 10
Sunday Morning E 5 - 15
Sunday Afternoon N 5 - 15
Sunday Night WSW 5 - 15
Central Cascades
Date Direction - Speed
Saturday Afternoon S 10 - 20
Saturday Night W 5 - 15
Sunday Morning E 5 - 15
Sunday Afternoon VAR 0 - 10
Sunday Night W 15 - 25
South Cascades
Date Direction - Speed
Saturday Afternoon SW 20 - 30
Saturday Night WSW 15 - 25
Sunday Morning S 10 - 20
Sunday Afternoon W 5 - 15
Sunday Night W 20 - 30

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 15 - 25 WSW 10 - 20 WSW 45 - 65 WSW 30 - 40
Saturday Night SW 15 - 25 SW 20 - 30 SW 25 - 35 SW 30 - 40
Sunday Morning SE 10 - 20 SE 10 - 20 ESE 20 - 30 SW 30 - 40
Sunday Afternoon ESE 15 - 25 SE 15 - 25 SSE 20 - 30 SSW 20 - 30
Northwest Cascades
Date Direction - Speed
Saturday Afternoon WSW 15 - 25
Saturday Night SW 15 - 25
Sunday Morning SE 10 - 20
Sunday Afternoon ESE 15 - 25
Sunday Night W 10 - 20
Northeast Cascades
Date Direction - Speed
Saturday Afternoon WSW 10 - 20
Saturday Night SW 20 - 30
Sunday Morning SE 10 - 20
Sunday Afternoon SE 15 - 25
Sunday Night WNW 15 - 25
Central Cascades
Date Direction - Speed
Saturday Afternoon WSW 45 - 65
Saturday Night SW 25 - 35
Sunday Morning ESE 20 - 30
Sunday Afternoon SSE 20 - 30
Sunday Night W 20 - 30
South Cascades
Date Direction - Speed
Saturday Afternoon WSW 30 - 40
Saturday Night SW 30 - 40
Sunday Morning SW 30 - 40
Sunday Afternoon SSW 20 - 30
Sunday Night W 30 - 40

Extended Weather Synopsis for Monday through Wednesday

The upper-level low crosses the Cascades on Monday morning with cool air continuing to spread into the region and a moist westerly flow bringing light to moderate precipitation, particularly to the west slopes of the Cascades at relatively low snow levels on Monday. Monday night, the moist flow with moderate precipitation on the Cascade west slopes continues with snow levels in the Cascades below pass level.

Tuesday stays cool. Weak ridging develops and makes the precipitation more scattered, with some convergence likely. Precipitation generally shuts off and with clearing skies, mountain temperatures will be quite cool.

On Wednesday, easterly flow develops over our region as a Pacific System drops south toward California.

 

Extended Weather Forecast for Monday through Wednesday

Olympics, Washington Cascades and Mt. Hood Area
Date Weather
Monday Light to moderate rain and snow with moderate westerly flow\, possibly becoming moderate to heavy overnight Monday. Cooler than seasonal norms.
Tuesday Decreasing light rain and snow showers, heaviest in convergence. Snow showers and convergence ending around midnight, followed by clearing skies and cool temperatures. Cooler than seasonal norms.

Snow/Freezing Levels

Date Olympics Northwest Cascades Northeast Cascades Central Cascades South Cascades Easterly Flow in Passes
Monday Snow Level 2500' - 3500' 2500' - 3500' 3000' - 4000' 2500' - 3500' 2000' - 3000'
Monday Night Snow Level 3000' - 4000' 2000' - 3000' 2000' - 3000' 2000' - 3000' 2000' - 3000'
Tuesday Snow Level 2500' - 3500' 2000' - 3000' 3000' - 4000' 2500' - 3500' 2000' - 3000'
Tuesday Night Snow Level 1500' - 2500' 1000' - 2000' 0' - 1000' 1000' - 2000' 1500' - 2500'
Olympics
Date Elevation
Monday Snow Level
2500' - 3500'
Monday Night Snow Level
3000' - 4000'
Tuesday Snow Level
2500' - 3500'
Tuesday Night Snow Level
1500' - 2500'
Wednesday Snow Level
2000' - 3000'
Northwest Cascades
Date Elevation
Monday Snow Level
2500' - 3500'
Monday Night Snow Level
2000' - 3000'
Tuesday Snow Level
2000' - 3000'
Tuesday Night Snow Level
1000' - 2000'
Wednesday Snow Level
3000' - 4000'
Northeast Cascades
Date Elevation
Monday Snow Level
3000' - 4000'
Monday Night Snow Level
2000' - 3000'
Tuesday Snow Level
3000' - 4000'
Tuesday Night Snow Level
0' - 1000'
Wednesday Snow Level
3500' - 4500'
Central Cascades
Date Elevation
Monday Snow Level
2500' - 3500'
Monday Night Snow Level
2000' - 3000'
Tuesday Snow Level
2500' - 3500'
Tuesday Night Snow Level
1000' - 2000'
Wednesday Snow Level
3000' - 4000'
South Cascades
Date Elevation
Monday Snow Level
2000' - 3000'
Monday Night Snow Level
2000' - 3000'
Tuesday Snow Level
2000' - 3000'
Tuesday Night Snow Level
1500' - 2500'
Wednesday 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.