Issued: 2:07 PM PST Monday, December 28, 2020
by Robert Hahn

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

Weather Synopsis

The next 24 hours features the calm before a major storm cycle slams the region.

Monday night the Pacific Northwest sits under the ridge axis with clear skies and then increasing high clouds moving into the region after midnight. Temperatures should generally be slightly milder than Sunday night with inversion conditions developing once again, with E flow through the mountain gaps becoming light.

High and mid-level clouds increase on Tuesday as the next system starts breaking down the ridge. Light precipitation might reach the coastline by the end of the day. For most locations, winds should start increasing but will remain light. However, moderate ridgeline winds can be expected at Mt Hood.

Tuesday night, moisture increases ahead of a frontal system becoming moderate to heavy at times after midnight. Temperatures should stay cool with E light E flow in the Cascades, but the Olympics will experience rising snow levels up to 4500 ft by morning. Winds will ramp up significantly. Expect strong ridgeline winds throughout the region after midnight. SW flow will focus the heaviest precipitation on Mt. Baker and the Mountain Loop areas.

A secondary frontal band should move across the region on Wednesday bringing the heaviest precipitation. Expect around 1" of water equivalent during daylight hours. Models indicate significant upper-level support for heavy precipitation with winds strengthening until a frontal passage expected around Mid-day. Winds and snowfall should gradually start to relent after this time.

There remains uncertainty regarding the timing of fronts and precipitation amounts with this storm, but many areas should see 12" or more of snow by late Wednesday.

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
Monday Night Clear skies in the evening, then increasing high clouds thereafter.
Tuesday High clouds lowering and thickening with a slight chance of rain or snow late in the day.
Monday Night Clear skies in the evening, then increasing high clouds thereafter.
Tuesday High clouds lowering and thickening with a slight chance of rain or snow late in the day.
Monday Night Clear skies in the evening, then increasing high clouds thereafter.
Tuesday High clouds lowering and thickening.
Monday Night Clear skies in the evening, then increasing high clouds thereafter.
Tuesday High clouds lowering and thickening.
Monday Night Clear skies in the evening, then increasing high clouds thereafter. Light E flow at pass level.
Tuesday High clouds lowering and thickening. Light E flow at pass level becoming variable or light westerly.
Monday Night Clear skies in the evening, then increasing high clouds thereafter. Light E flow at pass level.
Tuesday High clouds lowering and thickening. Light E flow at pass level becoming variable or light westerly.
Monday Night Clear skies in the evening, then increasing high clouds thereafter.
Tuesday High clouds lowering and thickening.
Monday Night Clear skies in the evening, then increasing high clouds thereafter.
Tuesday High clouds in the morning, then lowering and thickening in the afternoon.
Monday Night Clear skies in the evening, then increasing high clouds thereafter.
Tuesday High clouds in the morning, then lowering and thickening in the afternoon.
Monday Night Clear skies in the evening, then increasing high clouds thereafter.
Tuesday High clouds in the morning, then lowering and thickening in the afternoon.

Issued: 2:07 PM PST Monday, December 28, 2020

Precipitation (in)

Monday Night Tuesday Tuesday Night Wednesday
4 pm - 4 am 4 am - 4 pm 4 pm - 4 am 4 am - 4 pm
Hurricane Ridge 0 0 0.25 - 0.50 0.75
Mt Baker Ski Area 0 0 0.75 1.00
Mt. Loop - Barlow Pass 0 0 0.50 - 0.75 1.00 - 1.50
Stevens Pass 0 0 0.25 - 0.50 0.75 -1.00
Snoqualmie Pass 0 0 0.50 1.00 - 1.50
Crystal Mt 0 0 0.25 0.50 - 0.75
Paradise 0 0 0.75 1.50
White Pass 0 0 0.25 0.50 - 0.75
Washington Pass 0 0 0.25 0.75
Mission Ridge 0 0 LT 0.25 0.25
Salmon la Sac - Gallagher Head 0 0 0.25 - 0.50 0.75
Tieton River - Darland Mt. 0 0 0.25 0.50
Mt Hood Meadows 0 0 LT 0.25 0.75 -1.00
Timberline 0 0 0.25 1.00
Hurricane Ridge Precipitation (in)
Monday Night 0
Tuesday 0
Tuesday Night 0.25 - 0.50
Wednesday 0.75
Mt Baker Ski Area Precipitation (in)
Monday Night 0
Tuesday 0
Tuesday Night 0.75
Wednesday 1.00
Mt. Loop - Barlow Pass Precipitation (in)
Monday Night 0
Tuesday 0
Tuesday Night 0.50 - 0.75
Wednesday 1.00 - 1.50
Stevens Pass Precipitation (in)
Monday Night 0
Tuesday 0
Tuesday Night 0.25 - 0.50
Wednesday 0.75 -1.00
Snoqualmie Pass Precipitation (in)
Monday Night 0
Tuesday 0
Tuesday Night 0.50
Wednesday 1.00 - 1.50
Crystal Mt Precipitation (in)
Monday Night 0
Tuesday 0
Tuesday Night 0.25
Wednesday 0.50 - 0.75
Paradise Precipitation (in)
Monday Night 0
Tuesday 0
Tuesday Night 0.75
Wednesday 1.50
White Pass Precipitation (in)
Monday Night 0
Tuesday 0
Tuesday Night 0.25
Wednesday 0.50 - 0.75
Washington Pass Precipitation (in)
Monday Night 0
Tuesday 0
Tuesday Night 0.25
Wednesday 0.75
Mission Ridge Precipitation (in)
Monday Night 0
Tuesday 0
Tuesday Night LT 0.25
Wednesday 0.25
Salmon la Sac - Gallagher Head Precipitation (in)
Monday Night 0
Tuesday 0
Tuesday Night 0.25 - 0.50
Wednesday 0.75
Tieton River - Darland Mt. Precipitation (in)
Monday Night 0
Tuesday 0
Tuesday Night 0.25
Wednesday 0.50
Mt Hood Meadows Precipitation (in)
Monday Night 0
Tuesday 0
Tuesday Night LT 0.25
Wednesday 0.75 -1.00
Timberline Precipitation (in)
Monday Night 0
Tuesday 0
Tuesday Night 0.25
Wednesday 1.00

Issued: 2:07 PM PST Monday, December 28, 2020

Snow Level (ft)

Monday Evening* Monday Night* Tuesday Morning* Tuesday Afternoon Tuesday Evening* Tuesday Night* Wednesday Morning* Wednesday Afternoon
Olympics 4000' 4000' 4000' 5500' 3500' 4500' 5500' 4500'
West North 3500' 2500' 2000' 3000' 2500' 2000' 2500' 3500'
West Central 3500' 2500' 3000' 3500' 3000' 2000' 2500' 3000'
West South 4000' 3000' 3000' 4000' 3000' 2000' 2500' 3500'
Stevens Pass 3000' 2000' 2500' 3000' 1500' 1500' 2000' 2000'
Snoqualmie Pass 3500' 2500' 3000' 4000' 3000' 2000' 2500' 2500'
East North 2500' 1500' 1500' 2500' 1000' 1000' 1000' 1000'
East Central 2500' 2000' 2500' 2500' 1500' 1500' 1500' 2000'
East South 3500' 2500' 2500' 4000' 3000' 2500' 2000' 3000'
Mt. Hood 4500' 4000' 4500' 6000' 4500' 4500' 4500' 5000'
Olympics Elevation
Monday Evening* 4000'
Monday Night* 4000'
Tuesday Morning* 4000'
Tuesday Afternoon 5500'
Tuesday Evening* 3500'
Tuesday Night* 4500'
Wednesday Morning* 5500'
Wednesday Afternoon 4500'
West North Elevation
Monday Evening* 3500'
Monday Night* 2500'
Tuesday Morning* 2000'
Tuesday Afternoon 3000'
Tuesday Evening* 2500'
Tuesday Night* 2000'
Wednesday Morning* 2500'
Wednesday Afternoon 3500'
West Central Elevation
Monday Evening* 3500'
Monday Night* 2500'
Tuesday Morning* 3000'
Tuesday Afternoon 3500'
Tuesday Evening* 3000'
Tuesday Night* 2000'
Wednesday Morning* 2500'
Wednesday Afternoon 3000'
West South Elevation
Monday Evening* 4000'
Monday Night* 3000'
Tuesday Morning* 3000'
Tuesday Afternoon 4000'
Tuesday Evening* 3000'
Tuesday Night* 2000'
Wednesday Morning* 2500'
Wednesday Afternoon 3500'
Stevens Pass Elevation
Monday Evening* 3000'
Monday Night* 2000'
Tuesday Morning* 2500'
Tuesday Afternoon 3000'
Tuesday Evening* 1500'
Tuesday Night* 1500'
Wednesday Morning* 2000'
Wednesday Afternoon 2000'
Snoqualmie Pass Elevation
Monday Evening* 3500'
Monday Night* 2500'
Tuesday Morning* 3000'
Tuesday Afternoon 4000'
Tuesday Evening* 3000'
Tuesday Night* 2000'
Wednesday Morning* 2500'
Wednesday Afternoon 2500'
East North Elevation
Monday Evening* 2500'
Monday Night* 1500'
Tuesday Morning* 1500'
Tuesday Afternoon 2500'
Tuesday Evening* 1000'
Tuesday Night* 1000'
Wednesday Morning* 1000'
Wednesday Afternoon 1000'
East Central Elevation
Monday Evening* 2500'
Monday Night* 2000'
Tuesday Morning* 2500'
Tuesday Afternoon 2500'
Tuesday Evening* 1500'
Tuesday Night* 1500'
Wednesday Morning* 1500'
Wednesday Afternoon 2000'
East South Elevation
Monday Evening* 3500'
Monday Night* 2500'
Tuesday Morning* 2500'
Tuesday Afternoon 4000'
Tuesday Evening* 3000'
Tuesday Night* 2500'
Wednesday Morning* 2000'
Wednesday Afternoon 3000'
Mt. Hood Elevation
Monday Evening* 4500'
Monday Night* 4000'
Tuesday Morning* 4500'
Tuesday Afternoon 6000'
Tuesday Evening* 4500'
Tuesday Night* 4500'
Wednesday Morning* 4500'
Wednesday Afternoon 5000'

Issued: 2:07 PM PST Monday, December 28, 2020

5000' Temperatures (°F)

Monday Night Tuesday
Max / Min Max / Min
Olympics 26 / 23 31 / 25
West North 24 / 23 28 / 22
West Central 26 / 24 29 / 23
West South 27 / 25 34 / 24
Stevens Pass 25 / 23 31 / 23
Snoqualmie Pass 25 / 24 30 / 22
East North 24 / 21 29 / 22
East Central 25 / 24 31 / 24
East South 26 / 25 34 / 25
Mt. Hood 30 / 28 38 / 27
Olympics 5000' Temperature Forecast
(Max / Min)
Monday Night 26 / 23
Tuesday 31 / 25
West North 5000' Temperature Forecast
(Max / Min)
Monday Night 24 / 23
Tuesday 28 / 22
West Central 5000' Temperature Forecast
(Max / Min)
Monday Night 26 / 24
Tuesday 29 / 23
West South 5000' Temperature Forecast
(Max / Min)
Monday Night 27 / 25
Tuesday 34 / 24
Stevens Pass 5000' Temperature Forecast
(Max / Min)
Monday Night 25 / 23
Tuesday 31 / 23
Snoqualmie Pass 5000' Temperature Forecast
(Max / Min)
Monday Night 25 / 24
Tuesday 30 / 22
East North 5000' Temperature Forecast
(Max / Min)
Monday Night 24 / 21
Tuesday 29 / 22
East Central 5000' Temperature Forecast
(Max / Min)
Monday Night 25 / 24
Tuesday 31 / 24
East South 5000' Temperature Forecast
(Max / Min)
Monday Night 26 / 25
Tuesday 34 / 25
Mt. Hood 5000' Temperature Forecast
(Max / Min)
Monday Night 30 / 28
Tuesday 38 / 27

Issued: 2:07 PM PST Monday, December 28, 2020

Ridgeline Winds (mph)

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

Issued: 2:07 PM PST Monday, December 28, 2020

Extended Weather Synopsis

The upper low or trough associated with Wednesday's front should move across the region Wednesday night, bringing continued moderate snow showers. On Thursday, the trough slides east of the area with drying NW flow aloft. Thursday night, a flattening offshore ridge moves over the region with very light mountain-enhanced snowfall spilling over the ridge on westerly flow. Another major system arrives on Friday with a deep trough just offshore. This one looks potentially even more potent than the mid-week storm. With rain and snow ramping up throughout the day Friday. SSW winds should bring in milder air and snow may be dependent upon a battle between this warming and E flow at places like Snoqualmie Pass.

Extended Snow Level (ft)

Wednesday Night Thursday Thursday Night Friday *
West North 2500' 2500' 2500' 3000'
Snoqualmie Pass 3000' 2500' 2500' 3500'
Mt. Hood 3500' 3500' 3500' 5500'
West North Elevation
Wednesday Night 2500'
Thursday 2500'
Thursday Night 2500'
Friday * 3000'
Snoqualmie Pass Elevation
Wednesday Night 3000'
Thursday 2500'
Thursday Night 2500'
Friday * 3500'
Mt. Hood Elevation
Wednesday Night 3500'
Thursday 3500'
Thursday Night 3500'
Friday * 5500'

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

Previous forecast from Dec 28, 2020

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’.