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Mountain Weather Forecast

Issued: 4:00 PM PST Tuesday, January 16, 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 Tuesday & Wednesday

A shortwave trough follows in the wake of a weakening cold front, bringing moist SW flow, narrow bands of light to moderate rain, and a cooler air mass to our region on Tuesday. The trough will lift north during the day on Tuesday, cutting off moisture from south to north. Showers will linger in the Olympics and NW Cascades through the afternoon and evening hours.

Well offshore, an open low will be closing off and ejecting toward the central coast of British Columbia on Tuesday and Wednesday. More locally, Tuesday night will feature a break in the action and light SE winds ahead of this storm system.

On Wednesday, the warm front will lift northward during the morning hours, bringing light precipitation, but a big warm-up during the late morning at the tail end of the precipitation. Pass level easterlies should insulate the passes from the warming until the late morning hours. Wednesday afternoon the frontal rain band will move over the Olympics and progresses eastward across the Cascades during the late afternoon/early evening hours bringing moderate to heavy rain to most areas with high elevation snow. Areas exposed to southerly winds will receive moderate to strong crest-level winds prior to frontal passage in the Cascades around midnight. Moderate SW flow follows the frontal passage.

 

 

Weather forecast for Tuesday & Wednesday

Olympics
Date Weather
Tuesday Decreasing rain and snow showers, in isolated moderate rain bands.
Tuesday Night Fair with high clouds increasing.
Wednesday Light rain and snow developing, becoming light to moderate in the afternoon.
Moderate rain and snow showers becoming light and more isolated.
Washington Cascades near and west of the Crest including Stevens, Snoqualmie and White Passes
Date Weather
Tuesday Mostly cloudy skies in the north and mostly sunny skies in the south. Decreasing isolated moderate intensity rain bands, most sustained Mt. Baker area.
Tuesday Night Light rain and snow showers ending in the evening hours in the north. Low clouds lingering in the evening hours, becoming mostly clear after midnight.
Wednesday Light rain and snow developing, mainly from Mt. Rainier northward. The light rain and snow lingers in the north in the afternoon while the south sees mostly cloudy skies. Another round of rain and snow arrives very late in the day.
Increasing moderate to heavy rain in the evening hours. Light to moderate rain and snow showers after midnight.
East Slopes of the Washington Cascades
Date Weather
Tuesday Light rain and snow showers ending in the north. Partly sunny skies in the north, mostly sunny skies in the south.
Tuesday Night Partly cloudy in the evening hours, becoming mostly clear after midnight.
Wednesday Light rain and snow developing in the central and northern parts during the mid-day hours. Otherwise, mostly cloudy.
Increasing moderate rain in the evening hours. Light to moderate rain and snow showers after midnight.
Mt. Hood
Date Weather
Tuesday Partly sunny skies with isolated light to moderate rain bands.
Tuesday Night Mostly clear with increasing high clouds after midnight.
Wednesday Mostly cloudy.
Moderate rain, occasionally heavy.

Snow Level/Freezing Level in feet

Date Olympics Northwest Cascades Northeast Cascades Central Cascades South Cascades Easterly Flow in Passes
Tuesday Afternoon Snow Level 3500' 3500' 3500' 4000' 4500' *
Tuesday Night Snow Level 4500' 3000' 2000' 3000' 5000' *
Wednesday Morning Snow Level 8000' 4500' 3000' 6000' 8000' *
Wednesday Afternoon Snow Level 6000' 6000' 4000' 6000' 8000' *
Olympics
Date Elevation
Tuesday Afternoon Snow Level
3500'
Easterly Flow*
Tuesday Night Snow Level
4500'
Easterly Flow*
Wednesday Morning Snow Level
8000'
Easterly Flow*
Wednesday Afternoon Snow Level
6000'
Easterly Flow*
Wednesday Night Snow Level
3500'
Easterly Flow*
Northwest Cascades
Date Elevation
Tuesday Afternoon Snow Level
3500'
Easterly Flow*
Tuesday Night Snow Level
3000'
Easterly Flow*
Wednesday Morning Snow Level
4500'
Easterly Flow*
Wednesday Afternoon Snow Level
6000'
Easterly Flow*
Wednesday Night Snow Level
3500'
Easterly Flow*
Northeast Cascades
Date Elevation
Tuesday Afternoon Snow Level
3500'
Easterly Flow*
Tuesday Night Snow Level
2000'
Easterly Flow*
Wednesday Morning Snow Level
3000'
Easterly Flow*
Wednesday Afternoon Snow Level
4000'
Easterly Flow*
Wednesday Night Snow Level
3500'
Easterly Flow*
Central Cascades
Date Elevation
Tuesday Afternoon Snow Level
4000'
Easterly Flow*
Tuesday Night Snow Level
3000'
Easterly Flow*
Wednesday Morning Snow Level
6000'
Easterly Flow*
Wednesday Afternoon Snow Level
6000'
Easterly Flow*
Wednesday Night Snow Level
4000'
Easterly Flow*
South Cascades
Date Elevation
Tuesday Afternoon Snow Level
4500'
Easterly Flow*
Tuesday Night Snow Level
5000'
Easterly Flow*
Wednesday Morning Snow Level
8000'
Easterly Flow*
Wednesday Afternoon Snow Level
8000'
Easterly Flow*
Wednesday Night Snow Level
4500'
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 Wed Thu
Hurricane Ridge lt .25 1.00
Mt Baker Ski Area .75 2.50 - 3.00
Washington Pass .25 - .50 .75
Stevens Pass .25 .50
Snoqualmie Pass .25 .75 - 1.00
Mission Ridge lt .25 .25 - .50
Crystal Mt lt .10 1.00
Paradise lt .25 1.50
White Pass lt .10 .50 - .75
Mt Hood Meadows lt .10 .75 - 1.00

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

Date Direction - Speed
Tuesday Afternoon E 5 - 15
Tuesday Night E 15 - 25
Wednesday Morning E 20 - 30
Wednesday Afternoon E 25 - 35

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
Tuesday Afternoon SW 15 - 25 S 20 - 30 SW 10 - 20 SW 10 - 20
Tuesday Night SE 5 - 15 SSE 5 - 15 ESE 5 - 15 SE 10 - 20
Wednesday Morning S 30 - 40 SE 25 - 35 ESE 20 - 30 S 20 - 30
Wednesday Afternoon S 30 - 40 SE 40 - 60 ESE 20 - 30 S 20 - 30
Olympics
Date Elevation
Tuesday Afternoon SW 15 - 25
Tuesday Night SE 5 - 15
Wednesday Morning S 30 - 40
Wednesday Afternoon S 30 - 40
Wednesday Night SSW 25 - 35
Northwest Cascades
Date Elevation
Tuesday Afternoon S 20 - 30
Tuesday Night SSE 5 - 15
Wednesday Morning SE 25 - 35
Wednesday Afternoon SE 40 - 60
Wednesday Night S 20 - 30
Central Cascades
Date Elevation
Tuesday Afternoon SW 10 - 20
Tuesday Night ESE 5 - 15
Wednesday Morning ESE 20 - 30
Wednesday Afternoon ESE 20 - 30
Wednesday Night SW 20 - 30
South Cascades
Date Elevation
Tuesday Afternoon SW 10 - 20
Tuesday Night SE 10 - 20
Wednesday Morning S 20 - 30
Wednesday Afternoon S 20 - 30
Wednesday Night WSW 20 - 30
Olympics
Date Direction - Speed
Tuesday Afternoon SW 15 - 25
Tuesday Night SE 5 - 15
Wednesday Morning S 30 - 40
Wednesday Afternoon S 30 - 40
Wednesday Night SSW 25 - 35
Northwest Cascades
Date Direction - Speed
Tuesday Afternoon S 20 - 30
Tuesday Night SSE 5 - 15
Wednesday Morning SE 25 - 35
Wednesday Afternoon SE 40 - 60
Wednesday Night S 20 - 30
Central Cascades
Date Direction - Speed
Tuesday Afternoon SW 10 - 20
Tuesday Night ESE 5 - 15
Wednesday Morning ESE 20 - 30
Wednesday Afternoon ESE 20 - 30
Wednesday Night SW 20 - 30
South Cascades
Date Direction - Speed
Tuesday Afternoon SW 10 - 20
Tuesday Night SE 10 - 20
Wednesday Morning S 20 - 30
Wednesday Afternoon S 20 - 30
Wednesday Night WSW 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
Tuesday Afternoon SSW 25 - 35 SSW 30 - 40 SW 30 - 40 WSW 25 - 35
Tuesday Night SW 30 - 40 SW 20 - 30 SW 30 - 40 SW 30 - 40
Wednesday Morning SSW 40 - 60 SSW 40 - 60 SSW 40 - 60 SSW 40 - 60
Wednesday Afternoon SSW 60 - 80 SSW 50 - 70 SSW 65 - 85 SSW 60 - 80
Northwest Cascades
Date Direction - Speed
Tuesday Afternoon SSW 25 - 35
Tuesday Night SW 30 - 40
Wednesday Morning SSW 40 - 60
Wednesday Afternoon SSW 60 - 80
Wednesday Night SW 40 - 60
Northeast Cascades
Date Direction - Speed
Tuesday Afternoon SSW 30 - 40
Tuesday Night SW 20 - 30
Wednesday Morning SSW 40 - 60
Wednesday Afternoon SSW 50 - 70
Wednesday Night SW 40 - 60
Central Cascades
Date Direction - Speed
Tuesday Afternoon SW 30 - 40
Tuesday Night SW 30 - 40
Wednesday Morning SSW 40 - 60
Wednesday Afternoon SSW 65 - 85
Wednesday Night SW 40 - 60
South Cascades
Date Direction - Speed
Tuesday Afternoon WSW 25 - 35
Tuesday Night SW 30 - 40
Wednesday Morning SSW 40 - 60
Wednesday Afternoon SSW 60 - 80
Wednesday Night SW 50 - 70

Extended Weather Synopsis for Thursday through Saturday

Following Wednesday night's frontal passage a deep trough digs in on Thursday through Saturday. Some energy drops south of the forecast area, but a consistent moist and cold generally SW flow spinning around a low off the NW tip of Vancouver Island Thursday through Saturday will bring significant and consistent snow to the Cascades under generally low snow levels.

The low will spawn a surface feature that should swing through on Saturday provided some precipitation enhancement under continued low snow levels.

Extended Weather Forecast for Thursday through Saturday

Olympics, Washington Cascades and Mt. Hood Area
Date Weather
Thursday Light to moderate rain and snow showers on a SW flow Thursday and Thursday night.
Friday Light to moderate rain and snow showers on a SW flow Friday and Friday night.

Snow/Freezing Levels

Date Olympics Northwest Cascades Northeast Cascades Central Cascades South Cascades Easterly Flow in Passes
Thursday Snow Level 2500' - 3500' 2000' - 3000' 2000' - 3000' 2000' - 3000' 3000' - 4000'
Thursday Night Snow Level 2000' - 3000' 1500' - 2500' 1500' - 2500' 1500' - 2500' 1500' - 2500'
Friday Snow Level 2500' - 3500' 2000' - 3000' 1500' - 2500' 2000' - 3000' 2000' - 3000'
Friday Night Snow Level 1500' - 2500' 1500' - 2500' 1500' - 2500' 1500' - 2500' 1500' - 2500'
Olympics
Date Elevation
Thursday Snow Level
2500' - 3500'
Thursday Night Snow Level
2000' - 3000'
Friday Snow Level
2500' - 3500'
Friday Night Snow Level
1500' - 2500'
Saturday Snow Level
2000' - 3000'
Northwest Cascades
Date Elevation
Thursday Snow Level
2000' - 3000'
Thursday Night Snow Level
1500' - 2500'
Friday Snow Level
2000' - 3000'
Friday Night Snow Level
1500' - 2500'
Saturday Snow Level
1500' - 2500'
Northeast Cascades
Date Elevation
Thursday Snow Level
2000' - 3000'
Thursday Night Snow Level
1500' - 2500'
Friday Snow Level
1500' - 2500'
Friday Night Snow Level
1500' - 2500'
Saturday Snow Level
1500' - 2500'
Central Cascades
Date Elevation
Thursday Snow Level
2000' - 3000'
Thursday Night Snow Level
1500' - 2500'
Friday Snow Level
2000' - 3000'
Friday Night Snow Level
1500' - 2500'
Saturday Snow Level
2000' - 3000'
South Cascades
Date Elevation
Thursday Snow Level
3000' - 4000'
Thursday Night Snow Level
1500' - 2500'
Friday Snow Level
2000' - 3000'
Friday Night Snow Level
1500' - 2500'
Saturday Snow Level
2500' - 3500'

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.