Issued: 1:57 PM PST Sunday, December 12, 2021
by Dennis D'Amico

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

Weather Synopsis

Showers continue to rotate inland from the SW to NE across the area this afternoon. This pattern of light to locally moderate shower activity in onshore flow at the surface and SW flow aloft will continue over the area through this evening. After a short break in the shower activity overnight, a weak surface low wobbling off of Vancouver Island will swing a weak upper level disturbance to the Olympics before daybreak Monday. This should bring slightly heavier snowfall to the Olympics before the band spreads inland during the morning hours. This will also briefly spike SE ridgeline winds late Sunday night through Monday morning. Snowfall may be moderate at times Monday morning along the east slopes of the Cascades with the passing frontal band thanks to SE winds adding an upslope component to the precipitation. Showers should decrease across the region in the afternoon and snow levels/temperatures will rebound slightly. 

Yet another weak feature emanating from the surface low parked offshore will rotate up across the area Monday night producing another round of light snow showers. On Tuesday, the upper level trough will shift inland and showers will become light and isolated.  

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
Sunday Night Light to occasionally moderate snow showers.
Monday Light to occasionally moderate snow showers.
Sunday Night Light to occasionally moderate snow showers becoming scattered showers around midnight.
Monday Light to occasionally moderate snow showers in the morning becoming mostly cloudy in the afternoon.
Sunday Night Light to occasionally moderate snow showers becoming scattered showers around midnight.
Monday Light snow showers in the morning becoming mostly cloudy in the afternoon.
Sunday Night Light to occasionally moderate snow showers becoming scattered showers around midnight.
Monday Light snow showers in the morning becoming mostly cloudy in the afternoon.
Sunday Night Light to occasionally moderate snow showers becoming scattered showers around midnight. Light east winds at Pass level becoming moderate after midnight.
Monday Light snow showers in the morning becoming mostly cloudy in the afternoon. Moderate east winds at Pass level becoming light in the afternoon.
Sunday Night Light to occasionally moderate snow showers becoming scattered showers around midnight. Light east winds at Pass level becoming moderate after midnight.
Monday Light snow showers in the morning becoming mostly cloudy in the afternoon. Moderate east winds at Pass level becoming light in the afternoon.
Sunday Night Cloudy with scattered light snow showers increasing late.
Monday Light to occasionally moderate snow showers in the morning becoming mostly cloudy in the afternoon.
Sunday Night Cloudy with scattered light snow showers increasing late.
Monday Light to occasionally moderate snow showers in the morning becoming mostly cloudy in the afternoon.
Sunday Night Cloudy with scattered light snow showers increasing late.
Monday Light to occasionally moderate snow showers in the morning becoming mostly cloudy in the afternoon.
Sunday Night Light to occasionally moderate snow showers.
Monday Light to occasionally moderate snow showers.

Issued: 1:57 PM PST Sunday, December 12, 2021

Precipitation (in)

Sunday Night Monday Monday Night Tuesday
4 pm - 4 am 4 am - 4 pm 4 pm - 4 am 4 am - 4 pm
Hurricane Ridge 0.25 - 0.50 0.25 - 0.50 0.25 LT 0.10
Mt Baker Ski Area 0.25 0.25 0.25 LT 0.10
Mt. Loop - Barlow Pass LT 0.25 LT 0.25 LT 0.25 LT 0.10
Stevens Pass LT 0.10 LT 0.10 LT 0.25 LT 0.10
Snoqualmie Pass LT 0.25 LT 0.25 LT 0.25 LT 0.10
Crystal Mt LT 0.25 LT 0.25 LT 0.10 LT 0.10
Paradise 0.25 LT 0.25 LT 0.25 LT 0.10
White Pass LT 0.25 LT 0.10 LT 0.10 LT 0.10
Washington Pass LT 0.25 LT 0.25 LT 0.10 0
Mission Ridge LT 0.25 0.25 LT 0.10 0
Salmon la Sac - Gallagher Head LT 0.25 0.25 LT 0.10 0
Tieton River - Darland Mt. LT 0.25 0.25 LT 0.10 0
Mt Hood Meadows 0.25 0.25 LT 0.25 LT 0.10
Timberline 0.25 0.25 0.25 LT 0.10
Hurricane Ridge Precipitation (in)
Sunday Night 0.25 - 0.50
Monday 0.25 - 0.50
Monday Night 0.25
Tuesday LT 0.10
Mt Baker Ski Area Precipitation (in)
Sunday Night 0.25
Monday 0.25
Monday Night 0.25
Tuesday LT 0.10
Mt. Loop - Barlow Pass Precipitation (in)
Sunday Night LT 0.25
Monday LT 0.25
Monday Night LT 0.25
Tuesday LT 0.10
Stevens Pass Precipitation (in)
Sunday Night LT 0.10
Monday LT 0.10
Monday Night LT 0.25
Tuesday LT 0.10
Snoqualmie Pass Precipitation (in)
Sunday Night LT 0.25
Monday LT 0.25
Monday Night LT 0.25
Tuesday LT 0.10
Crystal Mt Precipitation (in)
Sunday Night LT 0.25
Monday LT 0.25
Monday Night LT 0.10
Tuesday LT 0.10
Paradise Precipitation (in)
Sunday Night 0.25
Monday LT 0.25
Monday Night LT 0.25
Tuesday LT 0.10
White Pass Precipitation (in)
Sunday Night LT 0.25
Monday LT 0.10
Monday Night LT 0.10
Tuesday LT 0.10
Washington Pass Precipitation (in)
Sunday Night LT 0.25
Monday LT 0.25
Monday Night LT 0.10
Tuesday 0
Mission Ridge Precipitation (in)
Sunday Night LT 0.25
Monday 0.25
Monday Night LT 0.10
Tuesday 0
Salmon la Sac - Gallagher Head Precipitation (in)
Sunday Night LT 0.25
Monday 0.25
Monday Night LT 0.10
Tuesday 0
Tieton River - Darland Mt. Precipitation (in)
Sunday Night LT 0.25
Monday 0.25
Monday Night LT 0.10
Tuesday 0
Mt Hood Meadows Precipitation (in)
Sunday Night 0.25
Monday 0.25
Monday Night LT 0.25
Tuesday LT 0.10
Timberline Precipitation (in)
Sunday Night 0.25
Monday 0.25
Monday Night 0.25
Tuesday LT 0.10

Issued: 1:57 PM PST Sunday, December 12, 2021

Snow Level (ft)

Sunday Evening Sunday Night* Monday Morning Monday Afternoon Monday Evening Monday Night Tuesday Morning Tuesday Afternoon
Olympics 1500' 1500' 1000' 2000' 1500' 500' 1000' 1500'
West North 1000' 1000' 500' 2000' 1000' 500' 1000' 1500'
West Central 1000' 1000' 500' 2000' 1000' 500' 1000' 1500'
West South 1500' 1500' 1000' 2500' 1500' 500' 1000' 1500'
Stevens Pass 1000' 0 500' 2000' 1000' 500' 1000' 1500'
Snoqualmie Pass 1000' 1000' 500' 2000' 1000' 500' 1000' 1500'
East North 1000' 0 0 2000' 1000' 500' 1000' 1500'
East Central 1000' 0 0 2000' 1000' 500' 1000' 1500'
East South 1500' 1000' 1000' 2500' 1500' 500' 1000' 1500'
Mt. Hood 2000' 1500' 1500' 3000' 1500' 500' 1000' 1500'
Olympics Elevation
Sunday Evening 1500'
Sunday Night* 1500'
Monday Morning 1000'
Monday Afternoon 2000'
Monday Evening 1500'
Monday Night 500'
Tuesday Morning 1000'
Tuesday Afternoon 1500'
West North Elevation
Sunday Evening 1000'
Sunday Night* 1000'
Monday Morning 500'
Monday Afternoon 2000'
Monday Evening 1000'
Monday Night 500'
Tuesday Morning 1000'
Tuesday Afternoon 1500'
West Central Elevation
Sunday Evening 1000'
Sunday Night* 1000'
Monday Morning 500'
Monday Afternoon 2000'
Monday Evening 1000'
Monday Night 500'
Tuesday Morning 1000'
Tuesday Afternoon 1500'
West South Elevation
Sunday Evening 1500'
Sunday Night* 1500'
Monday Morning 1000'
Monday Afternoon 2500'
Monday Evening 1500'
Monday Night 500'
Tuesday Morning 1000'
Tuesday Afternoon 1500'
Stevens Pass Elevation
Sunday Evening 1000'
Sunday Night* 0'
Monday Morning 500'
Monday Afternoon 2000'
Monday Evening 1000'
Monday Night 500'
Tuesday Morning 1000'
Tuesday Afternoon 1500'
Snoqualmie Pass Elevation
Sunday Evening 1000'
Sunday Night* 1000'
Monday Morning 500'
Monday Afternoon 2000'
Monday Evening 1000'
Monday Night 500'
Tuesday Morning 1000'
Tuesday Afternoon 1500'
East North Elevation
Sunday Evening 1000'
Sunday Night* 0'
Monday Morning 0'
Monday Afternoon 2000'
Monday Evening 1000'
Monday Night 500'
Tuesday Morning 1000'
Tuesday Afternoon 1500'
East Central Elevation
Sunday Evening 1000'
Sunday Night* 0'
Monday Morning 0'
Monday Afternoon 2000'
Monday Evening 1000'
Monday Night 500'
Tuesday Morning 1000'
Tuesday Afternoon 1500'
East South Elevation
Sunday Evening 1500'
Sunday Night* 1000'
Monday Morning 1000'
Monday Afternoon 2500'
Monday Evening 1500'
Monday Night 500'
Tuesday Morning 1000'
Tuesday Afternoon 1500'
Mt. Hood Elevation
Sunday Evening 2000'
Sunday Night* 1500'
Monday Morning 1500'
Monday Afternoon 3000'
Monday Evening 1500'
Monday Night 500'
Tuesday Morning 1000'
Tuesday Afternoon 1500'

Issued: 1:57 PM PST Sunday, December 12, 2021

5000' Temperatures (°F)

Sunday Night Monday
Max / Min Max / Min
Olympics 20 / 15 25 / 19
West North 19 / 17 25 / 19
West Central 20 / 17 26 / 19
West South 22 / 18 28 / 21
Stevens Pass 21 / 17 26 / 19
Snoqualmie Pass 21 / 17 26 / 20
East North 18 / 15 26 / 18
East Central 21 / 17 27 / 18
East South 21 / 18 27 / 20
Mt. Hood 24 / 22 29 / 22
Olympics 5000' Temperature Forecast
(Max / Min)
Sunday Night 20 / 15
Monday 25 / 19
West North 5000' Temperature Forecast
(Max / Min)
Sunday Night 19 / 17
Monday 25 / 19
West Central 5000' Temperature Forecast
(Max / Min)
Sunday Night 20 / 17
Monday 26 / 19
West South 5000' Temperature Forecast
(Max / Min)
Sunday Night 22 / 18
Monday 28 / 21
Stevens Pass 5000' Temperature Forecast
(Max / Min)
Sunday Night 21 / 17
Monday 26 / 19
Snoqualmie Pass 5000' Temperature Forecast
(Max / Min)
Sunday Night 21 / 17
Monday 26 / 20
East North 5000' Temperature Forecast
(Max / Min)
Sunday Night 18 / 15
Monday 26 / 18
East Central 5000' Temperature Forecast
(Max / Min)
Sunday Night 21 / 17
Monday 27 / 18
East South 5000' Temperature Forecast
(Max / Min)
Sunday Night 21 / 18
Monday 27 / 20
Mt. Hood 5000' Temperature Forecast
(Max / Min)
Sunday Night 24 / 22
Monday 29 / 22

Issued: 1:57 PM PST Sunday, December 12, 2021

Ridgeline Winds (mph)

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

Issued: 1:57 PM PST Sunday, December 12, 2021

Extended Weather Synopsis

A frontal system will approach the area Tuesday night into Wednesday with most forecast models glancing the area with light snow before the system drops south and shunts the bulk of the precipitation into Oregon/Northern California.  Thursday should be a transition day with perhaps some leftover light showers while we wait for a higher profile storm over the weekend. Snow levels will remain low through the extended. 

Extended Snow Level (ft)

Tuesday Night* Wednesday * Wednesday Night Thursday
West North 500' 1500' 500' 1500'
Snoqualmie Pass 500' 1500' 500' 1500'
Mt. Hood 1000' 1500' 1500' 2000'
West North Elevation
Tuesday Night* 500'
Wednesday * 1500'
Wednesday Night 500'
Thursday 1500'
Snoqualmie Pass Elevation
Tuesday Night* 500'
Wednesday * 1500'
Wednesday Night 500'
Thursday 1500'
Mt. Hood Elevation
Tuesday Night* 1000'
Wednesday * 1500'
Wednesday Night 1500'
Thursday 2000'

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

Previous forecast from Dec 12, 2021

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’.