Issued: 3:17 PM PST Monday, December 25, 2017
by Robert Hahn

Jump to: Weather Forecast I Snow/Freezing Level I Precipitation I Free Winds 5k I Free Winds 9k I Extended Weather

Weather Synopsis for Monday & Thursday

Mmmmmerry Christmas! A cold low parked over Hudson's bay will continue to keep much of North America in a cold pattern and the Pacific Northwest is no exception as many areas of the lowlands and the mountains will wake up to a White Christmas on Monday morning. While the Puget sound region is chilly, colder air is entrenched east of the Cascades.

On Monday, a weakening upper level trough moves through on westerly flow during the morning and early afternoon hours, bringing a drying trend during over the course of the day.

On Monday night, a ridge builds offshore as the Northwest stays dry with light onshore flow, becoming calm in some areas.

On Tuesday, the ridge offshore continues to keep the Northwest dry with light westerly winds. In the North Central Pacific a low pressure spins in place and ejects a small chunk of energy under the weak ridge off our coast.

On Tuesday night, that same piece of shortwave moves into our forecast region, bringing some some light precipitation, but uncertainty remains regarding the track and level of organization (or lack thereof). Models agree that the system should break down the offshore ridge.

 

Weather Forecast

Olympics
Monday Cloudy.
Monday Night Partly clear.
Tuesday Increasing high clouds.
Tuesday Night Mostly cloudy with a chance of high clouds.
Washington Cascades near and west of the Crest including Stevens, Snoqualmie and White Passes
Monday Showers ending; mostly cloudy.
Monday Night Partly cloudy with low clouds likely near the passes.
Tuesday Increasing high clouds with scattered low-level clouds, most likely near the passes.
Tuesday Night Mostly cloudy with a chance of light snow.
East Slopes of the Washington Cascades
Monday Mostly cloudy.
Monday Night Mostly cloudy with low clouds likely near the inversion top.
Tuesday Increasing high clouds with low clouds near the inversion top.
Tuesday Night Mostly cloudy with a chance of light snow.
Mt. Hood
Monday Cloudy.
Monday Night Mostly cloudy in the evening, becoming mostly clear with low clouds at top of inversion on the east side.
Tuesday Increasing high clouds, becoming mostly cloudy in the afternoon.
Tuesday Night Mostly cloudy with a chance of light snow.

Issued: 3:17 PM PST Monday, December 25, 2017

Snow/Freezing Level (ft)

Hurricane Ridge Mt. Baker Washington Pass Leavenworth Stevens Pass Snoqualmie Pass Mt. Rainier, Crystal & White Pass Mt. Hood
Monday Afternoon Snow Level * 1000' 0' 500' ' ' 1000' ' 2000'
Monday Night Freezing Level * 1000' 1000' 1000' ' ' 1000' ' 2000'
Tuesday Morning Freezing Level * 2000' 1000' 1000' ' ' 1500' ' 2000'
Tuesday Afternoon Freezing Level * 2000' 1000' 1500' ' ' 2000' ' 2500'
Tuesday Night Snow Level * 2000' 500' 0' ' ' 1500' ' 3000'
Tuesday Night Snow Level ' ' ' ' ' ' ' '
Hurricane Ridge Elevation
Monday Afternoon Snow Level
1000'
(Easterly Flow *)
Monday Night Freezing Level
1000'
(Easterly Flow *)
Tuesday Morning Freezing Level
2000'
(Easterly Flow *)
Tuesday Afternoon Freezing Level
2000'
(Easterly Flow *)
Tuesday Night Snow Level
2000'
(Easterly Flow *)
Tuesday Night Snow Level
'
Mt. Baker Elevation
Monday Afternoon Snow Level
0'
(Easterly Flow *)
Monday Night Freezing Level
1000'
(Easterly Flow *)
Tuesday Morning Freezing Level
1000'
(Easterly Flow *)
Tuesday Afternoon Freezing Level
1000'
(Easterly Flow *)
Tuesday Night Snow Level
500'
(Easterly Flow *)
Tuesday Night Snow Level
'
Washington Pass Elevation
Monday Afternoon Snow Level
500'
(Easterly Flow *)
Monday Night Freezing Level
1000'
(Easterly Flow *)
Tuesday Morning Freezing Level
1000'
(Easterly Flow *)
Tuesday Afternoon Freezing Level
1500'
(Easterly Flow *)
Tuesday Night Snow Level
0'
(Easterly Flow *)
Tuesday Night Snow Level
'
Leavenworth Elevation
Monday Afternoon Snow Level
'
(Easterly Flow *)
Monday Night Freezing Level
'
(Easterly Flow *)
Tuesday Morning Freezing Level
'
(Easterly Flow *)
Tuesday Afternoon Freezing Level
'
(Easterly Flow *)
Tuesday Night Snow Level
'
(Easterly Flow *)
Tuesday Night Snow Level
'
Stevens Pass Elevation
Monday Afternoon Snow Level
'
(Easterly Flow *)
Monday Night Freezing Level
'
(Easterly Flow *)
Tuesday Morning Freezing Level
'
(Easterly Flow *)
Tuesday Afternoon Freezing Level
'
(Easterly Flow *)
Tuesday Night Snow Level
'
(Easterly Flow *)
Tuesday Night Snow Level
'
Snoqualmie Pass Elevation
Monday Afternoon Snow Level
1000'
(Easterly Flow *)
Monday Night Freezing Level
1000'
(Easterly Flow *)
Tuesday Morning Freezing Level
1500'
(Easterly Flow *)
Tuesday Afternoon Freezing Level
2000'
(Easterly Flow *)
Tuesday Night Snow Level
1500'
(Easterly Flow *)
Tuesday Night Snow Level
'
Mt. Rainier & Crystal Elevation
Monday Afternoon Snow Level
'
(Easterly Flow *)
Monday Night Freezing Level
'
(Easterly Flow *)
Tuesday Morning Freezing Level
'
(Easterly Flow *)
Tuesday Afternoon Freezing Level
'
(Easterly Flow *)
Tuesday Night Snow Level
'
(Easterly Flow *)
Tuesday Night Snow Level
'
Mt. Hood Elevation
Monday Afternoon Snow Level
2000'
(Easterly Flow *)
Monday Night Freezing Level
2000'
(Easterly Flow *)
Tuesday Morning Freezing Level
2000'
(Easterly Flow *)
Tuesday Afternoon Freezing Level
2500'
(Easterly Flow *)
Tuesday Night Snow Level
3000'
(Easterly Flow *)
Tuesday Night Snow Level
'

* Easterly flow in the Cascade Passes can cause locally lower Snow or Freezing levels than areas further west.
Freezing Level is when no precipitation is forecast.

Precipitation Forecast

Thursday Thursday
Hurricane Ridge LT 0.10 LT 0.10
Mt Baker Ski Area LT 0.10 LT 0.10
Washington Pass LT 0.10 LT 0.10
Stevens Pass LT 0.10 LT 0.10
Snoqualmie Pass LT 0.25 LT 0.10
Mission Ridge LT 0.10 LT 0.10
Crystal Mt LT 0.25 LT 0.10
Paradise 0.25 - 0.50 LT 0.25
White Pass LT 0.25 LT 0.10
Mt Hood Meadows 0 - 0.50 LT 0.25
Timberline LT 0.25 LT 0.25

LT = less than; WE or Water equivalent is the liquid water equivalent of melted snow in hundredths of inches. As a rough approximation 1 inch of snow = about .10 inches WE, or 10 inches of snow = about 1 inch WE.

Issued: 3:17 PM PST Monday, December 25, 2017

Free Winds at 5000' (mph)

Hurricane Ridge Mt. Baker Stevens to Snoqualmie Pass Mt. Rainier Mt. Hood
Monday Afternoon SW 5 - 15 VAR 0 - 10 W 5 - 15 --- - W 10 - 20
Monday Night VAR 0 - 10 SSW 5 - 15 VAR 0 - 10 --- - W 0 - 10
Tuesday Morning S 5 - 15 S 5 - 15 VAR 0 - 10 --- - SSW 5 - 15
Tuesday Afternoon SW 5 - 15 SSW 5 - 15 WSW 5 - 15 --- - WSW 10 - 20
Tuesday Night W 10 - 20 SW 5 - 15 W 10 - 20 --- - W 20 - 30
Tuesday Night --- - --- - --- - --- - --- -
Hurricane Ridge Elevation
Monday Afternoon SW 5 - 15
Monday Night VAR 0 - 10
Tuesday Morning S 5 - 15
Tuesday Afternoon SW 5 - 15
Tuesday Night W 10 - 20
Tuesday Night --- -
Mt. Baker Elevation
Monday Afternoon VAR 0 - 10
Monday Night SSW 5 - 15
Tuesday Morning S 5 - 15
Tuesday Afternoon SSW 5 - 15
Tuesday Night SW 5 - 15
Tuesday Night --- -
Stevens and Snoqualmie Pass Elevation
Monday Afternoon W 5 - 15
Monday Night VAR 0 - 10
Tuesday Morning VAR 0 - 10
Tuesday Afternoon WSW 5 - 15
Tuesday Night W 10 - 20
Tuesday Night --- -
Mt. Rainier Elevation
Monday Afternoon --- -
Monday Night --- -
Tuesday Morning --- -
Tuesday Afternoon --- -
Tuesday Night --- -
Tuesday Night --- -
Mt. Hood Elevation
Monday Afternoon W 10 - 20
Monday Night W 0 - 10
Tuesday Morning SSW 5 - 15
Tuesday Afternoon WSW 10 - 20
Tuesday Night W 20 - 30
Tuesday Night --- -
Hurricane Ridge Direction - Speed
Monday Afternoon SW 5 - 15
Monday Night VAR 0 - 10
Tuesday Morning S 5 - 15
Tuesday Afternoon SW 5 - 15
Tuesday Night W 10 - 20
Tuesday Night --- -
Mt. Baker Direction - Speed
Monday Afternoon VAR 0 - 10
Monday Night SSW 5 - 15
Tuesday Morning S 5 - 15
Tuesday Afternoon SSW 5 - 15
Tuesday Night SW 5 - 15
Tuesday Night --- -
Stevens and Snoqualmie Pass Direction - Speed
Monday Afternoon W 5 - 15
Monday Night VAR 0 - 10
Tuesday Morning VAR 0 - 10
Tuesday Afternoon WSW 5 - 15
Tuesday Night W 10 - 20
Tuesday Night --- -
Mt. Rainier Direction - Speed
Monday Afternoon --- -
Monday Night --- -
Tuesday Morning --- -
Tuesday Afternoon --- -
Tuesday Night --- -
Tuesday Night --- -
Mt. Hood Direction - Speed
Monday Afternoon W 10 - 20
Monday Night W 0 - 10
Tuesday Morning SSW 5 - 15
Tuesday Afternoon WSW 10 - 20
Tuesday Night W 20 - 30
Tuesday Night --- -

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.

Free Winds at 9000' (mph)

Mt. Baker Washington Pass Stevens to Snoqualmie Pass Mt. Rainier Mt. Hood
Monday Afternoon WSW 20 - 30 W 10 - 20 WNW 20 - 30 --- - W 35 - 45
Tuesday Afternoon W 15 - 25 W 10 - 20 W 20 - 30 --- - W 30 - 45
Monday Night W 10 - 20 W 10 - 20 W 15 - 25 --- - W 30 - 45
Tuesday Morning WSW 20 - 30 W 10 - 20 W 20 - 30 --- - W 25 - 35
Tuesday Night W 25 - 35 W 25 - 35 W 30 - 45 --- - W 40 - 60
Tuesday Night --- - --- - --- - --- - --- -
Mt. Baker Direction - Speed
Monday Afternoon WSW 20 - 30
Tuesday Afternoon W 15 - 25
Monday Night W 10 - 20
Tuesday Morning WSW 20 - 30
Tuesday Night W 25 - 35
Tuesday Night --- -
Washington Pass Direction - Speed
Monday Afternoon W 10 - 20
Tuesday Afternoon W 10 - 20
Monday Night W 10 - 20
Tuesday Morning W 10 - 20
Tuesday Night W 25 - 35
Tuesday Night --- -
Stevens and Snoqualmie Pass Direction - Speed
Monday Afternoon WNW 20 - 30
Tuesday Afternoon W 20 - 30
Monday Night W 15 - 25
Tuesday Morning W 20 - 30
Tuesday Night W 30 - 45
Tuesday Night --- -
Mt. Rainier Direction - Speed
Monday Afternoon --- -
Tuesday Afternoon --- -
Monday Night --- -
Tuesday Morning --- -
Tuesday Night --- -
Tuesday Night --- -
Mt. Hood Direction - Speed
Monday Afternoon W 35 - 45
Tuesday Afternoon W 30 - 45
Monday Night W 30 - 45
Tuesday Morning W 25 - 35
Tuesday Night W 40 - 60
Tuesday Night --- -

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.

Issued: 3:17 PM PST Monday, December 25, 2017

Extended Weather Synopsis for Thursday night through Thursday

Light to moderate WNW flow aloft will prevail during quiescent weather Wednesday through Thursday morning.

By Thursday the aforementioned upper level low in the North Pacific slides east toward British Columbia. The feature is associated with a frontal system which will arrive by mid-day Thursday. There may be a surface low attached. The storm should continued wind and precipitation through Thurday night.

On Friday W-SW winds remain elevated in the southern part of the forecast zones, but should diminish as the feature passes, leaving a moist onshore flow with continued, but lighter precipitation as the band of precipitation fills lifts slightly northward.

On Friday night, some models indicate the presence of a much stronger system also associated with the same upper level low now nearing British Columbia. However, there is considerable model disagreement.

Extended Weather

Olympics, Washington Cascades and Mt. Hood Area
Wednesday Fair weather with light W-NW winds becoming SW by evening in the Olympics. Some warming Olympics and West of Cascade Crest and light rain and snow will arrive over the forecast area Wednesday night. Thursday Strong W-SW 9000 foot winds and strong crest-level S-SW winds will pick up first in the Olympics during the late morning and by mid-day in the Cascades as precipitation becomes moderate to heavy with subtle warming during the day Thursday. Thursday night, the precipitation diminishes in the north part of the forecast zones, but may be very heavy in the south. Friday Friday, light to moderate precipitation should be over the entire forecast area on a moist W-SW flow.

Extended Snow/Freezing Levels

Mt. Baker Snoqualmie Pass Mt. Hood Easterly Flow *
Wednesday Snow Level 500' - 1500' 1500' - 3500' 3000' - 4500'
Wednesday Night Snow Level 2000' - 4000' 3000' - 4000' 3000' - 4500'
Thursday Snow Level 2500' - 3500' 3000' - 4000' 3000' - 4500'
Thursday Night Snow Level 3500' - 4500' 3000' - 4000' 6500' - 7500'
Friday Snow Level 3500' - 4500' 4000' - 5000' 7000' - 8000'
Mt. Baker Elevation
Wednesday Snow Level
500' - 1500'
Wednesday Night Snow Level
2000' - 4000'
Thursday Snow Level
2500' - 3500'
Thursday Night Snow Level
3500' - 4500'
Friday Snow Level
3500' - 4500'
Snoqualmie Pass Elevation
Wednesday Snow Level
1500' - 3500'
Wednesday Night Snow Level
3000' - 4000'
Thursday Snow Level
3000' - 4000'
Thursday Night Snow Level
3000' - 4000'
Friday Snow Level
4000' - 5000'
Mt. Hood Elevation
Wednesday Snow Level
3000' - 4500'
Wednesday Night Snow Level
3000' - 4500'
Thursday Snow Level
3000' - 4500'
Thursday Night Snow Level
6500' - 7500'
Friday Snow Level
7000' - 8000'

* Easterly flow in the Cascade Passes can cause locally lower Snow or Freezing levels than areas further west.
Freezing Level is when no precipitation is forecast.

Jump to: Weather Forecast I Snow/Freezing Level I Precipitation I Free Winds 5k I Free Winds 9k I Extended Weather

Previous forecast from Dec 25, 2017

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