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Mountain Weather Forecast

Issued: 3:01 PM 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 is moving slightly eastward, toward our region, during the day on Tuesday.

Tuesday afternoon, weakening and disorganized cloud signatures are moving toward the Pacific Northwest, but a band of light to moderate precipitation is currently moving over the Olympics and will arrive in the central and north Cascades by later this afternoon.

This moisture is associated with next approaching weak upper level trough which will bring a warm front across the region, scouring out the cooler air in place on Wednesday. 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.

A drying trend will limit moisture 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 Light rain or snow at times.
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 Increasing light rain or snow from Mt. Rainier northward during the late afternoon hours.
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. Very light rain or snow developing near the crest during the late afternoon hours, north of Mt. Rainier.
Tuesday Night Light rain and snow continues near the Cascade crest, north of Snoqualmie pass 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 Fair weather with low-level clouds with sun above. Freezing levels continuing to rise.
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 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 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 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 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 Afternoon Snow Level
3500'
Tuesday Night Snow Level
4000'
Wednesday Morning Snow Level
5000'
Wednesday Afternoon Snow Level
6000'
Wednesday Night Snow Level
6500'
South Cascades
Date Elevation
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 .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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 Afternoon NW 30 - 40
Tuesday Night NW 35 - 50
Wednesday Morning NW 46 - 50
Wednesday Afternoon WNW 30 - 40
Wednesday Night W 40 - 60

Extended Weather Synopsis for Thursday through Saturday

The compact, but better organized shortwave will begin impacting the region during the early morning hours on Thursday, bringing increasing moderate precipitation and moderate to strong westerly crest-level winds during the day Thursday along with a cooling trend. Mid to upper elevation locations are likely to see snow throughout this event, while lower-elevations such Snoqualmie pass probably won't see a changeover to snow until the evening hours on Thursday, shortly after the surface cold front moves across the region.

Winds will begin to decrease Thursday night as flow splits around the Pacific Northwest resulting from a branch of the jetstream carving a trough over the Pacific Northwest, edging out the prevalent high pressure for short-term residence. Post-frontal showers should continue Thursday night through Friday, but a weakening flow will limit moisture on Friday. The persistent high amplitude ridge rebounds offshore, cutting off the flow of weather systems all the way to Alaska.

Flow switches to a light northerly and northeasterly on Friday night, ushering some of the colder air of the season, briefly. 

On Saturday the high will move eastward to the near shore waters as the trough moves south to California and the four corners area. Temperatures will rebound to more seasonal norms by the end of the day on Saturday west of the Cascade crest, with quite cold air still in place to the east of the crest.

 

 

Extended Weather Forecast for Thursday through Saturday

Olympics, Washington Cascades and Mt. Hood Area
Date Weather
Thursday Stormy with increasing moderate rain and snow for the Washington Cascades and lighter rain and snow for the Olympics (morning) and Hood region (arriving late). Moderate to strong crest-level westerly winds. Lowering snow levels. Friday night, expect light to occasional moderate rain and snow showers mainly along the Cascade west slopes of the Cascades.
Friday Decreasing light snow showers ending in the afternoon, mainly west slopes of the Cascades. Cold air mass in place. Light winds. Friday night, mostly clear with very cold air arriving, particularly in the NE Cascades as winds shift to the NE. A few snow showers lingering near Mt. Hood during the early evening hours.

Snow/Freezing Levels

Date Olympics Northwest Cascades Northeast Cascades Central Cascades South Cascades Easterly Flow in Passes
Thursday Snow Level 3500' - 4500' 3500' - 4500' 3500' - 4500' 3500' - 4500' 7500' - 8500'
Thursday Night Snow Level 2000' - 3000' 2000' - 3000' 2000' - 3000' 2000' - 3000' 3000' - 5000'
Friday Snow Level 1000' - 2000' 1000' - 2000' 1000' - 2000' 2000' - 3000' 2000' - 3000'
Friday Night Freezing Level 1000' - 2000' 0' - 1000' 0' - 1000' 1000' - 2000' 1000' - 2000'
Olympics
Date Elevation
Thursday Snow Level
3500' - 4500'
Thursday Night Snow Level
2000' - 3000'
Friday Snow Level
1000' - 2000'
Friday Night Freezing Level
1000' - 2000'
Saturday Freezing Level
2500' - 4500'
Northwest Cascades
Date Elevation
Thursday Snow Level
3500' - 4500'
Thursday Night Snow Level
2000' - 3000'
Friday Snow Level
1000' - 2000'
Friday Night Freezing Level
0' - 1000'
Saturday Freezing Level
1500' - 3500'
Northeast Cascades
Date Elevation
Thursday Snow Level
3500' - 4500'
Thursday Night Snow Level
2000' - 3000'
Friday Snow Level
1000' - 2000'
Friday Night Freezing Level
0' - 1000'
Saturday Freezing Level
1500' - 3500'
Central Cascades
Date Elevation
Thursday Snow Level
3500' - 4500'
Thursday Night Snow Level
2000' - 3000'
Friday Snow Level
2000' - 3000'
Friday Night Freezing Level
1000' - 2000'
Saturday Freezing Level
2500' - 4500'
South Cascades
Date Elevation
Thursday Snow Level
7500' - 8500'
Thursday Night Snow Level
3000' - 5000'
Friday Snow Level
2000' - 3000'
Friday Night Freezing Level
1000' - 2000'
Saturday Freezing Level
3000' - 5000'

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.