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Mountain Weather Forecast

Issued: 7:12 AM PST Tuesday, January 2, 2018
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 Tuesday & Wednesday

A pair of weak disturbances will move through the upper level ridge centered over the inland NW over the next 24 hours, temporarily flattening the ridge. The first one passing through today will only bring mid and high level clouds, the second one tonight will bring a chance for some very light showers. Snow/freezing levels will stay mild through the short term and offshore easterly flow will stay in the light to moderate range throughout the short term. Low clouds and cooler temperatures will be seen in the Cascade Passes,  lower elevations along the east slopes of the Cascades and Mt. Hood.  

The ridge will briefly rebuild over the area Wednesday and general cloudiness should decrease during the day.  An open trough rotating up from a previously cut-off low pressure system off the California coast will eject northward Wednesday night, bringing a chance of light showers late Wednesday night to the Mt. Hood area. 

Weather forecast for Tuesday & Wednesday

Olympics
Date Weather
Tuesday Mostly cloudy with mid and high clouds. Mild.
Tuesday Night Cloudy with periods of very light rain or snow. Mild.
Wednesday Mostly cloudy in the morning becoming partly sunny in the afternoon. Mild.
Becoming cloudy overnight. Mild.
Washington Cascades near and west of the Crest including Stevens, Snoqualmie and White Passes
Date Weather
Tuesday Mostly cloudy with mid and high clouds. Low clouds, breezy east winds and cooler temperatures Cascade Passes.
Tuesday Night Cloudy with periods of very light rain or snow. Low clouds, breezy east winds and cooler temperatures Cascade Passes.
Wednesday Mostly cloudy in the morning becoming partly sunny in the afternoon. Low clouds, breezy east winds and cooler temperatures Cascade Passes.
Becoming cloudy overnight. Low clouds, breezy east winds and cooler temperatures Cascade Passes.
East Slopes of the Washington Cascades
Date Weather
Tuesday Mostly cloudy with mid and high clouds. Low clouds and cooler temperatures lower slopes.
Tuesday Night Cloudy with periods of very light rain or snow. Low clouds and cooler temperatures lower slopes.
Wednesday Mostly cloudy in the morning becoming partly sunny in the afternoon. Low clouds and cooler temperatures lower slopes.
Becoming cloudy overnight. Low clouds and cooler temperatures lower slopes.
Mt. Hood
Date Weather
Tuesday Partly to mostly cloudy with mid and high clouds. Low clouds and cooler temperatures lower slopes.
Tuesday Night Cloudy with periods of very light rain or snow. Low clouds and cooler temperatures lower slopes.
Wednesday Mostly cloudy in the morning becoming partly sunny in the afternoon. Low clouds and cooler temperatures lower slopes.
Becoming cloudy overnight with a chance of light rain or snow showers after midnight.

Snow Level/Freezing Level in feet

Date Olympics Northwest Cascades Northeast Cascades Central Cascades South Cascades Easterly Flow in Passes
Tuesday Freezing Level 9500' 9000' 8500' 9500' 10500' *
Tuesday Night Snow Level 6000' 6000' 5000' 6500' 7000' *
Wednesday Freezing Level 9000' 9000' 8000' 9000' 9500' *
Olympics
Date Elevation
Tuesday Freezing Level
9500'
Easterly Flow*
Tuesday Night Snow Level
6000'
Easterly Flow*
Wednesday Freezing Level
9000'
Easterly Flow*
Wednesday Night Freezing Level
8500'
Easterly Flow*
Northwest Cascades
Date Elevation
Tuesday Freezing Level
9000'
Easterly Flow*
Tuesday Night Snow Level
6000'
Easterly Flow*
Wednesday Freezing Level
9000'
Easterly Flow*
Wednesday Night Freezing Level
8500'
Easterly Flow*
Northeast Cascades
Date Elevation
Tuesday Freezing Level
8500'
Easterly Flow*
Tuesday Night Snow Level
5000'
Easterly Flow*
Wednesday Freezing Level
8000'
Easterly Flow*
Wednesday Night Freezing Level
8000'
Easterly Flow*
Central Cascades
Date Elevation
Tuesday Freezing Level
9500'
Easterly Flow*
Tuesday Night Snow Level
6500'
Easterly Flow*
Wednesday Freezing Level
9000'
Easterly Flow*
Wednesday Night Freezing Level
9000'
Easterly Flow*
South Cascades
Date Elevation
Tuesday Freezing Level
10500'
Easterly Flow*
Tuesday Night Snow Level
7000'
Easterly Flow*
Wednesday Freezing Level
9500'
Easterly Flow*
Wednesday Night Freezing Level
9000'
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 .10 0
Mt Baker Ski Area lt .10 0
Washington Pass lt .10 0
Stevens Pass lt .10 0
Snoqualmie Pass lt .10 0
Mission Ridge lt .10 0
Crystal Mt lt .10 0
Paradise lt .10 0
White Pass lt .10 0
Mt Hood Meadows lt .10 0

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

Date Direction - Speed
Tuesday Morning E 20 - 35
Tuesday Afternoon E 20 - 30
Tuesday Night E 20 - 30
Wednesday 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
Tuesday Morning SE 0 - 10 E 0 - 10 ESE 15 - 25 ESE 10 - 20
Tuesday Afternoon S 0 - 10 ESE 0 - 10 ESE 10 - 20 ESE 5 - 15
Tuesday Night SE 0 - 10 VAR 0 - 10 ESE 5 - 15 SE 0 - 10
Wednesday SE 0 - 10 E 0 - 10 ESE 10 - 20 E 5 - 15
Olympics
Date Elevation
Tuesday Morning SE 0 - 10
Tuesday Afternoon S 0 - 10
Tuesday Night SE 0 - 10
Wednesday SE 0 - 10
Wednesday Night S 0 - 10
Northwest Cascades
Date Elevation
Tuesday Morning E 0 - 10
Tuesday Afternoon ESE 0 - 10
Tuesday Night VAR 0 - 10
Wednesday E 0 - 10
Wednesday Night E 0 - 10
Central Cascades
Date Elevation
Tuesday Morning ESE 15 - 25
Tuesday Afternoon ESE 10 - 20
Tuesday Night ESE 5 - 15
Wednesday ESE 10 - 20
Wednesday Night ESE 10 - 20
South Cascades
Date Elevation
Tuesday Morning ESE 10 - 20
Tuesday Afternoon ESE 5 - 15
Tuesday Night SE 0 - 10
Wednesday E 5 - 15
Wednesday Night ESE 10 - 20
Olympics
Date Direction - Speed
Tuesday Morning SE 0 - 10
Tuesday Afternoon S 0 - 10
Tuesday Night SE 0 - 10
Wednesday SE 0 - 10
Wednesday Night S 0 - 10
Northwest Cascades
Date Direction - Speed
Tuesday Morning E 0 - 10
Tuesday Afternoon ESE 0 - 10
Tuesday Night VAR 0 - 10
Wednesday E 0 - 10
Wednesday Night E 0 - 10
Central Cascades
Date Direction - Speed
Tuesday Morning ESE 15 - 25
Tuesday Afternoon ESE 10 - 20
Tuesday Night ESE 5 - 15
Wednesday ESE 10 - 20
Wednesday Night ESE 10 - 20
South Cascades
Date Direction - Speed
Tuesday Morning ESE 10 - 20
Tuesday Afternoon ESE 5 - 15
Tuesday Night SE 0 - 10
Wednesday E 5 - 15
Wednesday Night ESE 10 - 20

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 Morning SW 0 - 10 SW 0 - 10 S 0 - 10 S 5 - 15
Tuesday Afternoon SW 10 - 20 SW 5 - 15 SSW 5 - 15 SW 10 - 20
Tuesday Night W 0 - 10 W 0 - 10 SW 15 - 25 SW 10 - 20
Wednesday SW 0 - 10 SW 0 - 10 SW 10 - 20 SW 5 - 15
Northwest Cascades
Date Direction - Speed
Tuesday Morning SW 0 - 10
Tuesday Afternoon SW 10 - 20
Tuesday Night W 0 - 10
Wednesday SW 0 - 10
Wednesday Night SSW 10 - 20
Northeast Cascades
Date Direction - Speed
Tuesday Morning SW 0 - 10
Tuesday Afternoon SW 5 - 15
Tuesday Night W 0 - 10
Wednesday SW 0 - 10
Wednesday Night SW 5 - 15
Central Cascades
Date Direction - Speed
Tuesday Morning S 0 - 10
Tuesday Afternoon SSW 5 - 15
Tuesday Night SW 15 - 25
Wednesday SW 10 - 20
Wednesday Night S 5 - 15
South Cascades
Date Direction - Speed
Tuesday Morning S 5 - 15
Tuesday Afternoon SW 10 - 20
Tuesday Night SW 10 - 20
Wednesday SW 5 - 15
Wednesday Night SSE 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.