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Mountain Weather Forecast

Issued: 7:42 AM PST Tuesday, February 6, 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

The Pacific Northwest will remain in a relatively stationary pattern on Tuesday and Wednesday with NW flow aloft driven by the gradient between a high pressure offshore and a deep low over Hudson's Bay. The high pressure should move slightly eastward, toward our region during the day on Tuesday.

Light drizzle or very light snow has been seen early Tuesday morning as a very weak convergence zone fizzles out from a long since departed system's post-frontal flow. 

The next approaching weak upper level trough will bring a warm front across the region, scouring out the cooler air in place. Warming will be significant late Tuesday night through Wednesday with most areas of the Cascades seeing a changeover to rain at 5000 ft around 4 AM on Wednesday, with a possible mix with rain at Washington Pass Wednesday early afternoon as warming spreads northward and to higher elevations throughout the day. Light rain and snow will arrive from Snoqualmie pass, northward, slightly increasing toward the Canadian border from Tuesday afternoon through through Wednesday morning.

Wednesday should witness a drying trend with mostly dry conditions by Wednesday afternoon in all areas except the Mt. Baker area, where some very light rain may linger.

Late Wednesday through Wednesday night, crest-level winds will increase from the moderate range to occasionally strong out ahead of a better organized shortwave poised to impact our region on Thursday. This system will feature a sharp cold front when it arrives.

Weather forecast for Tuesday & Wednesday

Olympics
Date Weather
Tuesday Increasing clouds with a chance of light rain or snow.
Tuesday Night Increasing light rain or snow, particularly after midnight.
Wednesday Partly cloudy.
Clouds increasing and lowering. W-SW winds becoming moderate to strong at Hurricane Ridge.
Washington Cascades near and west of the Crest including Stevens, Snoqualmie and White Passes
Date Weather
Tuesday Decreasing drizzle, light rain or snow showers in weak convergence over the central Cascades in the morning, ending. Then, increasing light rain or snow from Snoqualmie Pass northward from late morning onward.
Tuesday Night Light rain and snow continues from Snoqualmie Pass northward. Warming begins overnight.
Wednesday Light rain and high elevation snow showers decreasing or ending from Snoqualmie pass northward, but likely lingering near Mt. Baker in the afternoon.
Increasing light to to moderate rain or snow in the north by morning. Increasing alpine winds becoming moderate to strong.
East Slopes of the Washington Cascades
Date Weather
Tuesday Mostly sunny east of the Cascade crest with clouds spilling over near the crest. Increasing clouds and very light rain or snow developing near the crest form late morning onward.
Tuesday Night Light rain and snow continues near the Cascade crest with clear weather further east.
Wednesday Light rain or high elevation snow showers decreasing or ending during the morning hours near the Cascade Crest from Snoqualmie pass northward.
Increasing light to moderate rain or snow in the north by morning. Increasing alpine winds becoming moderate to strong.
Mt. Hood
Date Weather
Tuesday Partly to mostly cloudy in the morning with decreasing clouds in the afternoon. Freezing levels rising strongly during the day.
Tuesday Night Fair weather with mostly clear skies and high freezing levels.
Wednesday Mostly sunny skies. High freezing levels.
Mostly clear with high clouds increasing by morning.

Snow Level/Freezing Level in feet

Date Olympics Northwest Cascades Northeast Cascades Central Cascades South Cascades Easterly Flow in Passes
Tuesday Morning Snow Level 5000' 3000' 3500' 3500' 5500'
Tuesday Afternoon Snow Level 5500' 3500' 3500' 3500' 7500'
Tuesday Night Snow Level 6500' 3500' 3500' 4000' 8000'
Wednesday Morning Snow Level 7000' 4000' 4000' 5000' 8500'
Wednesday Afternoon Snow Level 7500' 5000' 5500' 6000' 9000'
Olympics
Date Elevation
Tuesday Morning Snow Level
5000'
Tuesday Afternoon Snow Level
5500'
Tuesday Night Snow Level
6500'
Wednesday Morning Snow Level
7000'
Wednesday Afternoon Snow Level
7500'
Wednesday Night Snow Level
7000'
Northwest Cascades
Date Elevation
Tuesday Morning Snow Level
3000'
Tuesday Afternoon Snow Level
3500'
Tuesday Night Snow Level
3500'
Wednesday Morning Snow Level
4000'
Wednesday Afternoon Snow Level
5000'
Wednesday Night Snow Level
5500'
Northeast Cascades
Date Elevation
Tuesday Morning Snow Level
3500'
Tuesday Afternoon Snow Level
3500'
Tuesday Night Snow Level
3500'
Wednesday Morning Snow Level
4000'
Wednesday Afternoon Snow Level
5500'
Wednesday Night Snow Level
5500'
Central Cascades
Date Elevation
Tuesday Morning Snow Level
3500'
Tuesday Afternoon Snow Level
3500'
Tuesday Night Snow Level
4000'
Wednesday Morning Snow Level
5000'
Wednesday Afternoon Snow Level
6000'
Wednesday Night Snow Level
7000'
South Cascades
Date Elevation
Tuesday Morning Snow Level
5500'
Tuesday Afternoon Snow Level
7500'
Tuesday Night Snow Level
8000'
Wednesday Morning Snow Level
8500'
Wednesday Afternoon Snow Level
9000'
Wednesday Night Snow Level
9000'

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

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

Date Direction - Speed
Tuesday Morning W 5 - 15
Tuesday Afternoon W 5 - 15
Tuesday Night W 10 - 20
Wednesday Morning W 15 - 25
Wednesday Afternoon W 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
Tuesday Morning W 10 - 20 SW 5 - 15 W 10 - 20 W 15 - 25
Tuesday Afternoon W 10 - 20 WSW 10 - 20 W 10 - 20 W 15 - 25
Tuesday Night W 20 - 30 WSW 15 - 25 W 10 - 20 WNW 20 - 30
Wednesday Morning W 20 - 30 WSW 10 - 20 W 15 - 25 WNW 15 - 25
Wednesday Afternoon W 15 - 25 W 15 - 25 W 15 - 25 W 20 - 30
Olympics
Date Elevation
Tuesday Morning W 10 - 20
Tuesday Afternoon W 10 - 20
Tuesday Night W 20 - 30
Wednesday Morning W 20 - 30
Wednesday Afternoon W 15 - 25
Wednesday Night WSW 30 - 50
Northwest Cascades
Date Elevation
Tuesday Morning SW 5 - 15
Tuesday Afternoon WSW 10 - 20
Tuesday Night WSW 15 - 25
Wednesday Morning WSW 10 - 20
Wednesday Afternoon W 15 - 25
Wednesday Night WSW 25 - 35
Central Cascades
Date Elevation
Tuesday Morning W 10 - 20
Tuesday Afternoon W 10 - 20
Tuesday Night W 10 - 20
Wednesday Morning W 15 - 25
Wednesday Afternoon W 15 - 25
Wednesday Night W 30 - 40
South Cascades
Date Elevation
Tuesday Morning W 15 - 25
Tuesday Afternoon W 15 - 25
Tuesday Night WNW 20 - 30
Wednesday Morning WNW 15 - 25
Wednesday Afternoon W 20 - 30
Wednesday Night WSW 25 - 35
Olympics
Date Direction - Speed
Tuesday Morning W 10 - 20
Tuesday Afternoon W 10 - 20
Tuesday Night W 20 - 30
Wednesday Morning W 20 - 30
Wednesday Afternoon W 15 - 25
Wednesday Night WSW 30 - 50
Northwest Cascades
Date Direction - Speed
Tuesday Morning SW 5 - 15
Tuesday Afternoon WSW 10 - 20
Tuesday Night WSW 15 - 25
Wednesday Morning WSW 10 - 20
Wednesday Afternoon W 15 - 25
Wednesday Night WSW 25 - 35
Central Cascades
Date Direction - Speed
Tuesday Morning W 10 - 20
Tuesday Afternoon W 10 - 20
Tuesday Night W 10 - 20
Wednesday Morning W 15 - 25
Wednesday Afternoon W 15 - 25
Wednesday Night W 30 - 40
South Cascades
Date Direction - Speed
Tuesday Morning W 15 - 25
Tuesday Afternoon W 15 - 25
Tuesday Night WNW 20 - 30
Wednesday Morning WNW 15 - 25
Wednesday Afternoon W 20 - 30
Wednesday Night WSW 25 - 35

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 WNW 30 - 40 WNW 25 - 35 NW 45 - 65 NW 45 - 65
Tuesday Afternoon NW 35 - 50 NW 35 - 50 NW 40 - 60 NW 30 - 40
Tuesday Night WNW 35 - 50 WNW 40 - 60 NW 40 - 60 NW 35 - 50
Wednesday Morning WNW 40 - 60 WNW 45 - 65 WNW 50 - 70 NW 46 - 50
Wednesday Afternoon W 45 - 65 W 55 - 75 W 60 - 80 WNW 30 - 40
Northwest Cascades
Date Direction - Speed
Tuesday Morning WNW 30 - 40
Tuesday Afternoon NW 35 - 50
Tuesday Night WNW 35 - 50
Wednesday Morning WNW 40 - 60
Wednesday Afternoon W 45 - 65
Wednesday Night WSW 55 - 75
Northeast Cascades
Date Direction - Speed
Tuesday Morning WNW 25 - 35
Tuesday Afternoon NW 35 - 50
Tuesday Night WNW 40 - 60
Wednesday Morning WNW 45 - 65
Wednesday Afternoon W 55 - 75
Wednesday Night WSW 60 - 80
Central Cascades
Date Direction - Speed
Tuesday Morning NW 45 - 65
Tuesday Afternoon NW 40 - 60
Tuesday Night NW 40 - 60
Wednesday Morning WNW 50 - 70
Wednesday Afternoon W 60 - 80
Wednesday Night WSW 65 - 85
South Cascades
Date Direction - Speed
Tuesday Morning NW 45 - 65
Tuesday Afternoon NW 30 - 40
Tuesday Night NW 35 - 50
Wednesday Morning NW 46 - 50
Wednesday Afternoon WNW 30 - 40
Wednesday Night W 40 - 60

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 between 2 - 3 PM.