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Mountain Weather Forecast

Issued: 2:08 PM PST Saturday, December 30, 2017
by Kenny Kramer

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

An upper trough moved across the PNW Saturday morning, with a periods of strong moist westerly flow. This maintained light to moderate orographic showers along the west slopes of the Cascades and volcanic peaks early Saturday at lowering snow levels. Showers in most areas are diminishing rapidly with many sun breaks appearing as high pressure begins to rebuild offshore.

The WNW mid level flow is causing a number of convergence bands extending from the north Puget Sound into the north central west slopes, towards Stevens Pass early Saturday afternoon.

The moist flow is weakening Saturday afternoon and should allow convergence zones to dissipate and showers to become scattered or end Saturday afternoon. 

A building ridge of high pressure should allow for continued dry weather and clearing from Saturday night through Sunday. Freezing levels will begin to rise Sunday in response to the building high pressure ridge. However, a shift to easterly winds in the passes will maintain cool air in the passes.

Weather forecast for Saturday & Sunday

Olympics
Date Weather
Saturday Afternoon Scattered light snow showers ending. Partly to mostly cloudy. Diminishing westerly winds.
Saturday Night Becoming mostly clear and cool. Light winds.
Sunday Mostly sunny with a warming trend. Light winds.
Mostly clear and warming.
Washington Cascades near and west of the Crest including Stevens, Snoqualmie and White Passes
Date Weather
Saturday Afternoon Light snow showers diminishing. Snow showers becoming isolated or ending late afternoon.
Saturday Night Decreasing clouds.
Sunday Mostly sunny with a warming trend, except remaining cool in the passes. Light winds.
Mostly clear.
East Slopes of the Washington Cascades
Date Weather
Saturday Afternoon Snow showers ending with gradual clearing. Diminishing winds.
Saturday Night Becoming mostly clear.
Sunday Mostly sunny with a warming trend, except remaining cool in the passes. Light winds.
Mostly clear.
Mt. Hood
Date Weather
Saturday Afternoon Light snow showers diminishing. Snow showers becoming isolated or ending late afternoon. Diminishing winds.
Saturday Night Becoming mostly clear. Light winds.
Sunday Mostly sunny with a warming trend. Light winds.
Mostly clear.

Snow Level/Freezing Level in feet

Date Olympics Northwest Cascades Northeast Cascades Central Cascades South Cascades Easterly Flow in Passes
Saturday Afternoon Snow Level 2000' 1000' 1000' 2000' 3000'
Saturday Night Freezing Level 3000' 2000' 2000' 3000' 4000' *
Sunday Morning Freezing Level 4000' 2000' 500' 4000' 7000' *
Sunday Afternoon Freezing Level 6500' 3500' 500' 6000' 7500' *
Olympics
Date Elevation
Saturday Afternoon Snow Level
2000'
Saturday Night Freezing Level
3000'
Easterly Flow*
Sunday Morning Freezing Level
4000'
Easterly Flow*
Sunday Afternoon Freezing Level
6500'
Easterly Flow*
Sunday Night Freezing Level
7000'
Easterly Flow*
Northwest Cascades
Date Elevation
Saturday Afternoon Snow Level
1000'
Saturday Night Freezing Level
2000'
Easterly Flow*
Sunday Morning Freezing Level
2000'
Easterly Flow*
Sunday Afternoon Freezing Level
3500'
Easterly Flow*
Sunday Night Freezing Level
5000'
Easterly Flow*
Northeast Cascades
Date Elevation
Saturday Afternoon Snow Level
1000'
Saturday Night Freezing Level
2000'
Easterly Flow*
Sunday Morning Freezing Level
500'
Easterly Flow*
Sunday Afternoon Freezing Level
500'
Easterly Flow*
Sunday Night Freezing Level
3000'
Easterly Flow*
Central Cascades
Date Elevation
Saturday Afternoon Snow Level
2000'
Saturday Night Freezing Level
3000'
Easterly Flow*
Sunday Morning Freezing Level
4000'
Easterly Flow*
Sunday Afternoon Freezing Level
6000'
Easterly Flow*
Sunday Night Freezing Level
6500'
Easterly Flow*
South Cascades
Date Elevation
Saturday Afternoon Snow Level
3000'
Saturday Night Freezing Level
4000'
Easterly Flow*
Sunday Morning Freezing Level
7000'
Easterly Flow*
Sunday Afternoon Freezing Level
7500'
Easterly Flow*
Sunday Night Freezing Level
7500'
Easterly Flow*

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

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

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

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 NW 20 - 30 NW 20 - 30 NW 25 - 35 NW 20 - 30
Saturday Night NW 10 - 20 NW 10 - 20 NW 10 - 20 NW 5 - 15
Sunday Morning NNW 10 - 20 NNW 10 - 20 NNW 10 - 20 WNW 5 - 15
Sunday Afternoon NW 10 - 20 NW 10 - 20 NW 10 - 20 NW 10 - 20
Northwest Cascades
Date Direction - Speed
Saturday Afternoon NW 20 - 30
Saturday Night NW 10 - 20
Sunday Morning NNW 10 - 20
Sunday Afternoon NW 10 - 20
Sunday Night NW 15 - 25
Northeast Cascades
Date Direction - Speed
Saturday Afternoon NW 20 - 30
Saturday Night NW 10 - 20
Sunday Morning NNW 10 - 20
Sunday Afternoon NW 10 - 20
Sunday Night NW 15 - 25
Central Cascades
Date Direction - Speed
Saturday Afternoon NW 25 - 35
Saturday Night NW 10 - 20
Sunday Morning NNW 10 - 20
Sunday Afternoon NW 10 - 20
Sunday Night NW 10 - 20
South Cascades
Date Direction - Speed
Saturday Afternoon NW 20 - 30
Saturday Night NW 5 - 15
Sunday Morning WNW 5 - 15
Sunday Afternoon NW 10 - 20
Sunday Night WNW 5 - 15

Extended Weather Synopsis for Monday through Wednesday

An upper level ridge will persist just offshore Monday and gradually move inland Tuesday and Wednesday. This should maintain mostly fair weather with light winds over the region.

Offshore low level flow should maintain cooler weather with possible fog in the lower Cascade Passes. Otherwise, freezing levels should rise with warming temperatures through the extended period.

A disturbance should approach from the south Wednesday, spreading mainly high clouds and a few light showers over the Mt Hood area. 

Extended Weather Forecast for Monday through Wednesday

Olympics, Washington Cascades and Mt. Hood Area
Date Weather
Monday A mostly sunny day and clear night. Mild with light winds.
Tuesday Mostly fair with some mid and high clouds at times.

Snow/Freezing Levels

Date Olympics Northwest Cascades Northeast Cascades Central Cascades South Cascades Easterly Flow in Passes
Monday Freezing Level 8000' - 9000' 6000' - 7000' 5000' - 6000' 7000' - 8000' 8000' - 9000' *
Monday Night Freezing Level 8000' - 9000' 6000' - 7000' 5000' - 6000' 7000' - 8000' 8000' - 9000' *
Tuesday Freezing Level 8500' - 9500' 8000' - 9000' 6500' - 7500' 8000' - 9000' 9000' - 10000' *
Tuesday Night Freezing Level 7500' - 8500' 6500' - 7500' 5000' - 6000' 7000' - 8000' 8000' - 9000' *
Olympics
Date Elevation
Monday Freezing Level
8000' - 9000'
Easterly Flow*
Monday Night Freezing Level
8000' - 9000'
Easterly Flow*
Tuesday Freezing Level
8500' - 9500'
Easterly Flow*
Tuesday Night Freezing Level
7500' - 8500'
Easterly Flow*
Wednesday Freezing Level
8500' - 9500'
Easterly Flow*
Northwest Cascades
Date Elevation
Monday Freezing Level
6000' - 7000'
Easterly Flow*
Monday Night Freezing Level
6000' - 7000'
Easterly Flow*
Tuesday Freezing Level
8000' - 9000'
Easterly Flow*
Tuesday Night Freezing Level
6500' - 7500'
Easterly Flow*
Wednesday Freezing Level
7000' - 8500'
Easterly Flow*
Northeast Cascades
Date Elevation
Monday Freezing Level
5000' - 6000'
Easterly Flow*
Monday Night Freezing Level
5000' - 6000'
Easterly Flow*
Tuesday Freezing Level
6500' - 7500'
Easterly Flow*
Tuesday Night Freezing Level
5000' - 6000'
Easterly Flow*
Wednesday Freezing Level
6000' - 7500'
Easterly Flow*
Central Cascades
Date Elevation
Monday Freezing Level
7000' - 8000'
Easterly Flow*
Monday Night Freezing Level
7000' - 8000'
Easterly Flow*
Tuesday Freezing Level
8000' - 9000'
Easterly Flow*
Tuesday Night Freezing Level
7000' - 8000'
Easterly Flow*
Wednesday Freezing Level
7500' - 8500'
Easterly Flow*
South Cascades
Date Elevation
Monday Freezing Level
8000' - 9000'
Easterly Flow*
Monday Night Freezing Level
8000' - 9000'
Easterly Flow*
Tuesday Freezing Level
9000' - 10000'
Easterly Flow*
Tuesday Night Freezing Level
8000' - 9000'
Easterly Flow*
Wednesday Freezing Level
8000' - 9000'
Easterly Flow*

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.