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Mountain Weather Forecast

Issued: 7:14 AM PST Sunday, December 31, 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 Sunday & Monday

An upper level ridge of high pressure is building northward along the coast of the PNW early Sunday. This is providing a cool and dry but diminishing NW flow aloft and has turned the low level winds to easterly through the lower Cascade passes and near the crest. Skies should be mostly sunny Sunday with a warming trend as the ridge nudges closer to the coast and gains strength. 

Cool easterly flow through the passes should maintain colder temperatures and maintain some low level clouds or fog in the passes and lower east slope approaches.

Otherwise, light winds, sunshine and warming temperatures will be the pattern in areas away from the passes and lower elevations.

The ridge builds northward along the coast on New Years Day to maintain this dry, fair weather pattern and provide further warming. 

Weather forecast for Sunday & Monday

Olympics
Date Weather
Sunday Mostly sunny with a warming trend. Light winds.
Sunday Night Mostly clear. Light winds.
Monday Mostly sunny, mild. Light winds.
Mostly clear and mild.
Washington Cascades near and west of the Crest including Stevens, Snoqualmie and White Passes
Date Weather
Sunday Mostly sunny with a warming trend volcanoes and higher elevations. Remaining cool in the passes with low clouds and areas of fog.
Sunday Night Mostly clear and mild higher elevations. Cool with areas of low clouds and fog lower elevations and passes.
Monday Mostly sunny and mild over the volcanoes and higher elevations. Remaining cool in the passes with low clouds and areas of fog.
Mostly clear and mild higher elevations. Cool with areas of low clouds and fog lower elevations and passes.
East Slopes of the Washington Cascades
Date Weather
Sunday Mostly sunny with a warming trend higher elevations. Remaining cool lower elevations with areas of low clouds or fog. Light winds.
Sunday Night Becoming mostly clear higher terrain. Cool with areas of low clouds and fog lower elevations.
Monday Mostly sunny and mild higher elevations. Cool lower elevations with areas of low clouds or fog. Light winds.
Mostly clear.
Mt. Hood
Date Weather
Sunday Sunny with a warming trend. Light winds.
Sunday Night Mostly clear and mild. Light winds.
Monday Mostly sunny and mild. Light winds.
Mostly clear.

Snow Level/Freezing Level in feet

Date Olympics Northwest Cascades Northeast Cascades Central Cascades South Cascades Easterly Flow in Passes
Sunday Morning Freezing Level 4500' 2000' 1500' 3500' 6500' *
Sunday Afternoon Freezing Level 8000' 5000' 3000' 7000' 8500' *
Sunday Night Freezing Level 8000' 6000' 4000' 7000' 8500' *
Monday Morning Freezing Level 8000' 6000' 5500' 7500' 8500' *
Monday Afternoon Freezing Level 8500' 7000' 6500' 8000' 8500' *
Olympics
Date Elevation
Sunday Morning Freezing Level
4500'
Easterly Flow*
Sunday Afternoon Freezing Level
8000'
Easterly Flow*
Sunday Night Freezing Level
8000'
Easterly Flow*
Monday Morning Freezing Level
8000'
Easterly Flow*
Monday Afternoon Freezing Level
8500'
Easterly Flow*
Monday Night Freezing Level
8500'
Easterly Flow*
Northwest Cascades
Date Elevation
Sunday Morning Freezing Level
2000'
Easterly Flow*
Sunday Afternoon Freezing Level
5000'
Easterly Flow*
Sunday Night Freezing Level
6000'
Easterly Flow*
Monday Morning Freezing Level
6000'
Easterly Flow*
Monday Afternoon Freezing Level
7000'
Easterly Flow*
Monday Night Freezing Level
7000'
Easterly Flow*
Northeast Cascades
Date Elevation
Sunday Morning Freezing Level
1500'
Easterly Flow*
Sunday Afternoon Freezing Level
3000'
Easterly Flow*
Sunday Night Freezing Level
4000'
Easterly Flow*
Monday Morning Freezing Level
5500'
Easterly Flow*
Monday Afternoon Freezing Level
6500'
Easterly Flow*
Monday Night Freezing Level
6500'
Easterly Flow*
Central Cascades
Date Elevation
Sunday Morning Freezing Level
3500'
Easterly Flow*
Sunday Afternoon Freezing Level
7000'
Easterly Flow*
Sunday Night Freezing Level
7000'
Easterly Flow*
Monday Morning Freezing Level
7500'
Easterly Flow*
Monday Afternoon Freezing Level
8000'
Easterly Flow*
Monday Night Freezing Level
8000'
Easterly Flow*
South Cascades
Date Elevation
Sunday Morning Freezing Level
6500'
Easterly Flow*
Sunday Afternoon Freezing Level
8500'
Easterly Flow*
Sunday Night Freezing Level
8500'
Easterly Flow*
Monday Morning Freezing Level
8500'
Easterly Flow*
Monday Afternoon Freezing Level
8500'
Easterly Flow*
Monday Night Freezing Level
8500'
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 Mon Tue
Hurricane Ridge 0 0
Mt Baker Ski Area 0 0
Washington Pass 0 0
Stevens Pass 0 0
Snoqualmie Pass 0 0
Mission Ridge 0 0
Crystal Mt 0 0
Paradise 0 0
White Pass 0 0
Mt Hood Meadows 0 0

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

Date Direction - Speed
Sunday Morning E 10 - 20
Sunday Afternoon E 15 - 25
Sunday Night E 10 - 20
Monday Morning E 5 - 15
Monday Afternoon E 5 - 15

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
Sunday Morning E 5 - 15 E 0 - 10 E 10 - 20 E 10 - 20
Sunday Afternoon E 0 - 10 SE 0 - 10 ESE 15 - 25 ESE 5 - 10
Sunday Night VAR 0 - 10 VAR 0 - 10 ESE 0 - 10 SW 0 - 10
Monday Morning W 0 - 10 W 0 - 10 E 0 - 10 W 0 - 10
Monday Afternoon E 0 - 10 W 0 - 10 E 0 - 10 W 0 - 10
Olympics
Date Elevation
Sunday Morning E 5 - 15
Sunday Afternoon E 0 - 10
Sunday Night VAR 0 - 10
Monday Morning W 0 - 10
Monday Afternoon E 0 - 10
Monday Night E 0 - 10
Northwest Cascades
Date Elevation
Sunday Morning E 0 - 10
Sunday Afternoon SE 0 - 10
Sunday Night VAR 0 - 10
Monday Morning W 0 - 10
Monday Afternoon W 0 - 10
Monday Night E 0 - 10
Central Cascades
Date Elevation
Sunday Morning E 10 - 20
Sunday Afternoon ESE 15 - 25
Sunday Night ESE 0 - 10
Monday Morning E 0 - 10
Monday Afternoon E 0 - 10
Monday Night E 0 - 10
South Cascades
Date Elevation
Sunday Morning E 10 - 20
Sunday Afternoon ESE 5 - 10
Sunday Night SW 0 - 10
Monday Morning W 0 - 10
Monday Afternoon W 0 - 10
Monday Night ESE 0 - 10
Olympics
Date Direction - Speed
Sunday Morning E 5 - 15
Sunday Afternoon E 0 - 10
Sunday Night VAR 0 - 10
Monday Morning W 0 - 10
Monday Afternoon E 0 - 10
Monday Night E 0 - 10
Northwest Cascades
Date Direction - Speed
Sunday Morning E 0 - 10
Sunday Afternoon SE 0 - 10
Sunday Night VAR 0 - 10
Monday Morning W 0 - 10
Monday Afternoon W 0 - 10
Monday Night E 0 - 10
Central Cascades
Date Direction - Speed
Sunday Morning E 10 - 20
Sunday Afternoon ESE 15 - 25
Sunday Night ESE 0 - 10
Monday Morning E 0 - 10
Monday Afternoon E 0 - 10
Monday Night E 0 - 10
South Cascades
Date Direction - Speed
Sunday Morning E 10 - 20
Sunday Afternoon ESE 5 - 10
Sunday Night SW 0 - 10
Monday Morning W 0 - 10
Monday Afternoon W 0 - 10
Monday Night ESE 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
Sunday Morning NW 10 - 20 NW 10 - 20 NW 10 - 20 NNW 5 - 15
Sunday Afternoon NW 10 - 20 NW 10 - 20 NW 5 - 15 NW 5 - 15
Sunday Night NW 15 - 25 NW 15 - 25 NW 10 - 20 WNW 10 - 20
Monday Morning NW 10 - 20 NW 10 - 20 NW 10 - 20 WNW 5 - 15
Monday Afternoon NW 10 - 15 NW 10 - 15 NW 5 - 10 NW 5 - 10
Northwest Cascades
Date Direction - Speed
Sunday Morning NW 10 - 20
Sunday Afternoon NW 10 - 20
Sunday Night NW 15 - 25
Monday Morning NW 10 - 20
Monday Afternoon NW 10 - 15
Monday Night WNW 0 - 10
Northeast Cascades
Date Direction - Speed
Sunday Morning NW 10 - 20
Sunday Afternoon NW 10 - 20
Sunday Night NW 15 - 25
Monday Morning NW 10 - 20
Monday Afternoon NW 10 - 15
Monday Night WNW 0 - 10
Central Cascades
Date Direction - Speed
Sunday Morning NW 10 - 20
Sunday Afternoon NW 5 - 15
Sunday Night NW 10 - 20
Monday Morning NW 10 - 20
Monday Afternoon NW 5 - 10
Monday Night WNW 0 - 10
South Cascades
Date Direction - Speed
Sunday Morning NNW 5 - 15
Sunday Afternoon NW 5 - 15
Sunday Night WNW 10 - 20
Monday Morning WNW 5 - 15
Monday Afternoon NW 5 - 10
Monday Night WSW 0 - 10

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.