Issued: 2:35 PM PST Tuesday, December 29, 2020
by Robert Hahn

Jump to: Weather Forecast I Precipitation I Snow Level I 5000' Temps I Ridgeline Winds I Extended Weather

Weather Synopsis

On Monday afternoon, light rain and snow is moving into the Washington Coast region ahead of a significant system. Temperatures are in the 20's at low levels east of the Crest and with a cold air pool in place east of the Cascade Crest, the easterly flow should help keep many areas snow throughout the initial storm.

Tuesday night, pre-frontal moisture streams into the region on an increasing SW flow with an initial wave moving through the region overnight focusing on Washington State. Rain and snow should become heavy over much of Washington State by early Wednesday morning. The main frontal precipitation should arrive Wednesday with a broad area of moderate ridgeline SW winds that will be locally strong in favored locations such as Mt. Baker and Mt. Hood. At this time we think E flow will keep Snoqualmie Pass all snow, but snow levels will rise west of the Crest, so areas like Hurricane Ridge will see snow levels peak around 4500 ft on Wednesday morning.

A trough moves into the region Wednesday night with moderate rain and snow continuing as an upper-level low approaches. The low is currently slated to move into southern Washington and Oregon early Thursday with models diverging regarding the strength of the snow. Outliers have very heavy precipitation, but we have chosen a middle of the road solution with moderate rain and snow. Shower activity winds down as a temporary ridge pushes into the region late in the day.

Many locations should pick up 1-2 ft of snow by the end of the day Thursday. It's worth noting that while we typically associate a trough with cooler temperatures, the moderate winds with Wednesday's front will dispace some of the cold air pool and allow temperatures to moderate slightly from Wednesday onwards.

Weather Forecast

Olympics
West North
West Central
West South
Stevens Pass
Snoqualmie Pass
East North
East Central
East South
Mt. Hood
Use dropdown to select your zone
Tuesday Night Increasing light rain and snow in the evening becoming moderate overnight.
Wednesday Moderate rain and snow.
Tuesday Night Increasing light rain and snow in the evening becoming heavy overnight. Moderate to strong winds in thee early morning hours.
Wednesday Heavy rain and snow, easing late in the day. Gradual warming. Moderate to strong wind in the morning.
Tuesday Night Increasing light rain and snow in the evening becoming heavy overnight.
Wednesday Heavy rain and snow, easing late in the day. Gradual warming.
Tuesday Night Increasing light rain and snow in the evening becoming heavy overnight at Paradise, but staying light to moderate at Crystal and White Pass.
Wednesday Heavy rain and snow at Paradise, moderate rain and snow at White Pass and Crystal.
Tuesday Night Increasing light snow in the evening becoming moderate to heavy overnight. Light E winds at pass level.
Wednesday Heavy snow. Light E wind at pass level.
Tuesday Night Increasing light rain and snow in the evening becoming moderate to heavy overnight. Light to moderate E winds at pass level.
Wednesday Heavy rain and snow. Light to moderate E wind at pass level.
Tuesday Night Very light snow developing in the evening and becoming light to moderate overnight.
Wednesday Moderate snow.
Tuesday Night Very light snow developing in the evening and becoming moderate overnight.
Wednesday Moderate to heavy snow.
Tuesday Night Increasing light snow.
Wednesday Moderate snow.
Tuesday Night Light rain and snow developing in the early morning hours. Increasing moderate to strong ridgeline winds.
Wednesday Increasing snow throughout the day becoming heavy from late morning onwards. Decreasing moderate to strong ridgeline winds.

Issued: 2:35 PM PST Tuesday, December 29, 2020

Precipitation (in)

Tuesday Night Wednesday Wednesday Night Thursday
4 pm - 4 am 4 am - 4 pm 4 pm - 4 am 4 am - 4 pm
Hurricane Ridge 0.25 - 0.50 0.50 - 0.75 0.25 LT 0.10
Mt Baker Ski Area 0.75 1.00 - 1.50 0.50 LT 0.25
Mt. Loop - Barlow Pass 0.75 1.00 - 1.50 0.50 - 0.75 0.25 - 0.50
Stevens Pass 0.75 0.75 -1.00 0.25 - 0.50 0.25 - 0.50
Snoqualmie Pass 0.75 1.00 - 1.50 0.75 0.50
Crystal Mt 0.25 0.50 - 0.75 0.25 - 0.50 LT 0.25
Paradise 1.00 1.00 - 1.50 0.75 -1.00 0.50
White Pass 0.50 0.50 - 0.75 0.50 0.25
Washington Pass 0.25 0.50 - 0.75 LT 0.25 LT 0.10
Mission Ridge LT 0.25 0.25 - 0.50 LT 0.25 LT 0.10
Salmon la Sac - Gallagher Head 0.50 0.75 -1.00 0.50 0.25
Tieton River - Darland Mt. 0.25 0.50 0.25 - 0.50 LT 0.25
Mt Hood Meadows LT 0.25 0.75 -1.00 0.75 -1.00 0.50 - 0.75
Timberline LT 0.25 1.00 1.00 0.50 - 0.75
Hurricane Ridge Precipitation (in)
Tuesday Night 0.25 - 0.50
Wednesday 0.50 - 0.75
Wednesday Night 0.25
Thursday LT 0.10
Mt Baker Ski Area Precipitation (in)
Tuesday Night 0.75
Wednesday 1.00 - 1.50
Wednesday Night 0.50
Thursday LT 0.25
Mt. Loop - Barlow Pass Precipitation (in)
Tuesday Night 0.75
Wednesday 1.00 - 1.50
Wednesday Night 0.50 - 0.75
Thursday 0.25 - 0.50
Stevens Pass Precipitation (in)
Tuesday Night 0.75
Wednesday 0.75 -1.00
Wednesday Night 0.25 - 0.50
Thursday 0.25 - 0.50
Snoqualmie Pass Precipitation (in)
Tuesday Night 0.75
Wednesday 1.00 - 1.50
Wednesday Night 0.75
Thursday 0.50
Crystal Mt Precipitation (in)
Tuesday Night 0.25
Wednesday 0.50 - 0.75
Wednesday Night 0.25 - 0.50
Thursday LT 0.25
Paradise Precipitation (in)
Tuesday Night 1.00
Wednesday 1.00 - 1.50
Wednesday Night 0.75 -1.00
Thursday 0.50
White Pass Precipitation (in)
Tuesday Night 0.50
Wednesday 0.50 - 0.75
Wednesday Night 0.50
Thursday 0.25
Washington Pass Precipitation (in)
Tuesday Night 0.25
Wednesday 0.50 - 0.75
Wednesday Night LT 0.25
Thursday LT 0.10
Mission Ridge Precipitation (in)
Tuesday Night LT 0.25
Wednesday 0.25 - 0.50
Wednesday Night LT 0.25
Thursday LT 0.10
Salmon la Sac - Gallagher Head Precipitation (in)
Tuesday Night 0.50
Wednesday 0.75 -1.00
Wednesday Night 0.50
Thursday 0.25
Tieton River - Darland Mt. Precipitation (in)
Tuesday Night 0.25
Wednesday 0.50
Wednesday Night 0.25 - 0.50
Thursday LT 0.25
Mt Hood Meadows Precipitation (in)
Tuesday Night LT 0.25
Wednesday 0.75 -1.00
Wednesday Night 0.75 -1.00
Thursday 0.50 - 0.75
Timberline Precipitation (in)
Tuesday Night LT 0.25
Wednesday 1.00
Wednesday Night 1.00
Thursday 0.50 - 0.75

Issued: 2:35 PM PST Tuesday, December 29, 2020

Snow Level (ft)

Tuesday Evening* Tuesday Night* Wednesday Morning* Wednesday Afternoon* Wednesday Evening* Wednesday Night* Thursday Morning* Thursday Afternoon*
Olympics 3000' 4000' 4500' 4000' 4000' 3500' 4000' 4500'
West North 2000' 2000' 2500' 3000' 3000' 3000' 3000' 3500'
West Central 2500' 2500' 3000' 2000' 2500' 3000' 3000' 3500'
West South 3000' 2500' 3000' 3000' 3000' 3000' 3000' 3500'
Stevens Pass 2500' 2000' 2000' 1500' 2000' 2500' 2500' 3500'
Snoqualmie Pass 2500' 2500' 2500' 2000' 2500' 2500' 3000' 3500'
East North 1500' 2000' 2000' 1500' 1500' 2000' 2000' 3500'
East Central 2000' 1500' 1500' 2000' 2000' 2000' 2500' 3500'
East South 3000' 2000' 3000' 3000' 3000' 3000' 3000' 4000'
Mt. Hood 4000' 3500' 3500' 3500' 3500' 3500' 3500' 3500'
Olympics Elevation
Tuesday Evening* 3000'
Tuesday Night* 4000'
Wednesday Morning* 4500'
Wednesday Afternoon* 4000'
Wednesday Evening* 4000'
Wednesday Night* 3500'
Thursday Morning* 4000'
Thursday Afternoon* 4500'
West North Elevation
Tuesday Evening* 2000'
Tuesday Night* 2000'
Wednesday Morning* 2500'
Wednesday Afternoon* 3000'
Wednesday Evening* 3000'
Wednesday Night* 3000'
Thursday Morning* 3000'
Thursday Afternoon* 3500'
West Central Elevation
Tuesday Evening* 2500'
Tuesday Night* 2500'
Wednesday Morning* 3000'
Wednesday Afternoon* 2000'
Wednesday Evening* 2500'
Wednesday Night* 3000'
Thursday Morning* 3000'
Thursday Afternoon* 3500'
West South Elevation
Tuesday Evening* 3000'
Tuesday Night* 2500'
Wednesday Morning* 3000'
Wednesday Afternoon* 3000'
Wednesday Evening* 3000'
Wednesday Night* 3000'
Thursday Morning* 3000'
Thursday Afternoon* 3500'
Stevens Pass Elevation
Tuesday Evening* 2500'
Tuesday Night* 2000'
Wednesday Morning* 2000'
Wednesday Afternoon* 1500'
Wednesday Evening* 2000'
Wednesday Night* 2500'
Thursday Morning* 2500'
Thursday Afternoon* 3500'
Snoqualmie Pass Elevation
Tuesday Evening* 2500'
Tuesday Night* 2500'
Wednesday Morning* 2500'
Wednesday Afternoon* 2000'
Wednesday Evening* 2500'
Wednesday Night* 2500'
Thursday Morning* 3000'
Thursday Afternoon* 3500'
East North Elevation
Tuesday Evening* 1500'
Tuesday Night* 2000'
Wednesday Morning* 2000'
Wednesday Afternoon* 1500'
Wednesday Evening* 1500'
Wednesday Night* 2000'
Thursday Morning* 2000'
Thursday Afternoon* 3500'
East Central Elevation
Tuesday Evening* 2000'
Tuesday Night* 1500'
Wednesday Morning* 1500'
Wednesday Afternoon* 2000'
Wednesday Evening* 2000'
Wednesday Night* 2000'
Thursday Morning* 2500'
Thursday Afternoon* 3500'
East South Elevation
Tuesday Evening* 3000'
Tuesday Night* 2000'
Wednesday Morning* 3000'
Wednesday Afternoon* 3000'
Wednesday Evening* 3000'
Wednesday Night* 3000'
Thursday Morning* 3000'
Thursday Afternoon* 4000'
Mt. Hood Elevation
Tuesday Evening* 4000'
Tuesday Night* 3500'
Wednesday Morning* 3500'
Wednesday Afternoon* 3500'
Wednesday Evening* 3500'
Wednesday Night* 3500'
Thursday Morning* 3500'
Thursday Afternoon* 3500'

Issued: 2:35 PM PST Tuesday, December 29, 2020

5000' Temperatures (°F)

Tuesday Night Wednesday
Max / Min Max / Min
Olympics 30 / 25 31 / 29
West North 27 / 24 29 / 27
West Central 28 / 24 30 / 27
West South 28 / 25 29 / 28
Stevens Pass 25 / 23 27 / 24
Snoqualmie Pass 26 / 23 27 / 25
East North 20 / 18 22 / 19
East Central 25 / 22 26 / 24
East South 28 / 23 30 / 26
Mt. Hood 32 / 26 32 / 27
Olympics 5000' Temperature Forecast
(Max / Min)
Tuesday Night 30 / 25
Wednesday 31 / 29
West North 5000' Temperature Forecast
(Max / Min)
Tuesday Night 27 / 24
Wednesday 29 / 27
West Central 5000' Temperature Forecast
(Max / Min)
Tuesday Night 28 / 24
Wednesday 30 / 27
West South 5000' Temperature Forecast
(Max / Min)
Tuesday Night 28 / 25
Wednesday 29 / 28
Stevens Pass 5000' Temperature Forecast
(Max / Min)
Tuesday Night 25 / 23
Wednesday 27 / 24
Snoqualmie Pass 5000' Temperature Forecast
(Max / Min)
Tuesday Night 26 / 23
Wednesday 27 / 25
East North 5000' Temperature Forecast
(Max / Min)
Tuesday Night 20 / 18
Wednesday 22 / 19
East Central 5000' Temperature Forecast
(Max / Min)
Tuesday Night 25 / 22
Wednesday 26 / 24
East South 5000' Temperature Forecast
(Max / Min)
Tuesday Night 28 / 23
Wednesday 30 / 26
Mt. Hood 5000' Temperature Forecast
(Max / Min)
Tuesday Night 32 / 26
Wednesday 32 / 27

Issued: 2:35 PM PST Tuesday, December 29, 2020

Ridgeline Winds (mph)

Tuesday Evening Tuesday Night Wednesday Morning Wednesday Afternoon
Olympics SW 15-25 SSW 20-30 SSW 25-35 SW 15-25
West North S 10-20 SSW 25-35 S 25-35 SSW 15-25
West Central SSW 10-20 SW 10-20 SSW 15-25 SSW 10-20
West South SSW 10-20 SSW 10-20 SW 20-30 SW 10-20
Stevens Pass SW 5-15 SW 0-10 SSW 5-15 SSW 5-15
Snoqualmie Pass SW 10-20 SW 5-15 S 5-15 S 5-15
East North SW 5-15 SW 5-15 SSW 5-15 S 5-15
East Central WSW 15-25 WSW 10-20 SW 15-25 SW 15-25
East South WSW 10-20 WSW 10-20 WSW 15-25 SW 10-20
Mt. Hood WSW 25-35 SW 25-35 SW 25-35 SW 20-30
Olympics Ridgeline Winds (mph)
Tuesday Evening SW 15-25
Tuesday Night SSW 20-30
Wednesday Morning SSW 25-35
Wednesday Afternoon SW 15-25
West North Ridgeline Winds (mph)
Tuesday Evening S 10-20
Tuesday Night SSW 25-35
Wednesday Morning S 25-35
Wednesday Afternoon SSW 15-25
West Central Ridgeline Winds (mph)
Tuesday Evening SSW 10-20
Tuesday Night SW 10-20
Wednesday Morning SSW 15-25
Wednesday Afternoon SSW 10-20
West South Ridgeline Winds (mph)
Tuesday Evening SSW 10-20
Tuesday Night SSW 10-20
Wednesday Morning SW 20-30
Wednesday Afternoon SW 10-20
Stevens Pass Ridgeline Winds (mph)
Tuesday Evening SW 5-15
Tuesday Night SW 0-10
Wednesday Morning SSW 5-15
Wednesday Afternoon SSW 5-15
Snoqualmie Pass Ridgeline Winds (mph)
Tuesday Evening SW 10-20
Tuesday Night SW 5-15
Wednesday Morning S 5-15
Wednesday Afternoon S 5-15
East North Ridgeline Winds (mph)
Tuesday Evening SW 5-15
Tuesday Night SW 5-15
Wednesday Morning SSW 5-15
Wednesday Afternoon S 5-15
East Central Ridgeline Winds (mph)
Tuesday Evening WSW 15-25
Tuesday Night WSW 10-20
Wednesday Morning SW 15-25
Wednesday Afternoon SW 15-25
East South Ridgeline Winds (mph)
Tuesday Evening WSW 10-20
Tuesday Night WSW 10-20
Wednesday Morning WSW 15-25
Wednesday Afternoon SW 10-20
Mt. Hood Ridgeline Winds (mph)
Tuesday Evening WSW 25-35
Tuesday Night SW 25-35
Wednesday Morning SW 25-35
Wednesday Afternoon SW 20-30

Issued: 2:35 PM PST Tuesday, December 29, 2020

Extended Weather Synopsis

Showers diminish Thursday evening and then rain/snow picks up again after midnight as warm-frontal moisture lifts across the region through Friday morning. This should bring light rain and snow along with rising snow levels as the region sits in the warm sector most of the day Friday. E flow should help keep the Cascade Passes slightly cooler, but the cold pool will not be as well developed as it was with Wednesday's storm. Expect a cold frontal passage Friday evening with WSW flow and post-frontal showers lingering overnight. A developing low and attached frontal system approach on Saturday with increasing moderate rain and snow possibly becoming heavy in some areas in the afternoon.

Extended Snow Level (ft)

Thursday Night* Friday * Friday Night* Saturday *
West North 3500' 4500' 4000' 3500'
Snoqualmie Pass 3500' 4500' 4500' 3500'
Mt. Hood 3500' 6000' 5000' 4000'
West North Elevation
Thursday Night* 3500'
Friday * 4500'
Friday Night* 4000'
Saturday * 3500'
Snoqualmie Pass Elevation
Thursday Night* 3500'
Friday * 4500'
Friday Night* 4500'
Saturday * 3500'
Mt. Hood Elevation
Thursday Night* 3500'
Friday * 6000'
Friday Night* 5000'
Saturday * 4000'

Jump to: Weather Forecast I Precipitation I Snow Level I 5000' Temps I Ridgeline Winds I Extended Weather

Previous forecast from Dec 29, 2020

The mountain weather forecast underwent format changes on December 10th, 2020. To learn more about zone name changes, click here.

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.

The 5000’ temperature forecast does not imply a trend over the 12 hr period and only represents the max and min temperatures within a 12 hr period in the zone. The 6-hr snow level forecast, the forecast discussion, and weather forecast sections may add detail regarding temperature trends.

The snow level forecast represents the general snow level over a 6 hr time period. Freezing levels are forecast when precipitation is not expected.

*Easterly or offshore flow is highlighted with an asterisk when we expect relatively cool east winds in the major Cascade Passes. Easterly flow will often lead to temperature inversions and is a key variable for forecasting precipitation type in the Cascade Passes. Strong easterly flow events can affect terrain on a more regional scale.

Ridgeline winds are the average wind speed and direction over a 6 hr time period.

The wind forecast represents an elevation range instead of a single elevation slice. The elevation range overlaps with the near and above treeline elevation bands in the avalanche forecast and differs per zone.

Wind direction indicates the direction the wind originates or comes from on the 16-point compass rose.

Water Equivalent (WE) is the liquid water equivalent of all precipitation types; rain, snow, ice pellets, etc., forecast to the hundredth of an inch at specific locations. To use WE as a proxy for snowfall amounts, start with a snow to water ratio of 10:1 (10 inches of snow = 1 inch WE). Temperatures at or near freezing will generally have a lower ratio (heavy wet snow) and very cold temperatures can have a much higher ratio (dry fluffy snow).

The label LT, is shorthand for ‘less than’.