Issued: 2:07 PM PST Sunday, December 19, 2021
by Robert Hahn

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

Weather Synopsis

A modest low-pressure center sits off the California coast on Sunday afternoon with a band of warm frontal precipitation extending northeast into northern Oregon and very southern Washington. The low ejects northeast, guided by a deeper low-pressure center further offshore. This trajectory lifts the warm front northward into Washington State. This should bring some moderate snowfall to the Oregon and southern Washington Cascades Sunday night and Monday, with light to moderate snow making it as far north as Washington Pass by Monday afternoon. The front gradually loses energy and cohesion, with only light precipitation remaining Monday night and a few showers or sprinkles on Tuesday.

As the warm front lifts northward, snow levels should rise across the southern Cascades - most notably late Monday and Monday night, with warming reaching the Canadian border by Tuesday afternoon. The positioning of the lower pressure offshore creates a period of easterly winds which should peak late Sunday night into Monday morning but continues to keep the passes relatively cooler through Tuesday. The effect on the pass temperatures and lowering snow levels will be more significant than the strength of the winds.

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 Clear in the evening with high clouds arriving and thickening in the early morning hours.
Monday Cloudy early, then increasing light snow.
Sunday Night Clear in the evening with high clouds arriving and thickening overnight.
Monday Cloudy. Light snow possibly developing during the afternoon.
Sunday Night High clouds lowering and thickening overnight.
Monday Increasing light snow, heaviest southern part.
Sunday Night High clouds lowering and thickening in the Mt. Rainier area during the evening, then Increasing light to snow, heaviest White Pass. Moderate snow, heavy at times, for Mt. St. Helens and Mt. Adams.
Monday Moderate snow, heavy at times for at Paradise, Mt. St. Helens, and Mt. Adams. Moderate snow for Crystal and White Pass.
Sunday Night High clouds lowering and thickening with light snow possibly developing by morning. Moderate E winds decreasing slightly overnight at the Pass.
Monday Periods of light to moderate snow.
Sunday Night High clouds lowering and thickening with light snow developing overnight. Moderate E winds decreasing slightly overnight at the Pass.
Monday Periods of moderate snow.
Sunday Night High clouds lowering and thickening overnight.
Monday Light snow possible from late morning onwards.
Sunday Night High clouds lowering and thickening in the evening, then light snow developing in the early morning hours.
Monday Light to moderate snow.
Sunday Night Increasing light to moderate snow from south to north.
Monday Moderate snow.
Sunday Night Moderate to heavy snow. Strong ridgeline wind gusts.
Monday Moderate to heavy snow. Strong ridgeline wind gusts.

Issued: 2:07 PM PST Sunday, December 19, 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 LT 0.10 LT 0.10 LT 0.10
Mt Baker Ski Area 0 0 0 LT 0.10
Mt. Loop - Barlow Pass 0 0.25 LT 0.10 LT 0.10
Stevens Pass 0 0.25 LT 0.25 LT 0.10
Snoqualmie Pass LT 0.10 0.50 0.25 LT 0.10
Crystal Mt LT 0.25 0.25 - 0.50 LT 0.10 0
Paradise 0.25 0.75 0.25 LT 0.10
White Pass 0.25 - 0.50 0.50 - 0.75 LT 0.25 0
Washington Pass 0 LT 0.10 LT 0.10 0
Mission Ridge LT 0.10 LT 0.25 LT 0.10 0
Salmon la Sac - Gallagher Head LT 0.10 0.25 - 0.50 LT 0.25 0
Tieton River - Darland Mt. 0.25 - 0.50 0.50 LT 0.10 0
Mt Hood Meadows 0.75 0.75 LT 0.25 0
Timberline 0.75 0.75 0.25 0
Hurricane Ridge Precipitation (in)
Sunday Night 0
Monday LT 0.10
Monday Night LT 0.10
Tuesday LT 0.10
Mt Baker Ski Area Precipitation (in)
Sunday Night 0
Monday 0
Monday Night 0
Tuesday LT 0.10
Mt. Loop - Barlow Pass Precipitation (in)
Sunday Night 0
Monday 0.25
Monday Night LT 0.10
Tuesday LT 0.10
Stevens Pass Precipitation (in)
Sunday Night 0
Monday 0.25
Monday Night LT 0.25
Tuesday LT 0.10
Snoqualmie Pass Precipitation (in)
Sunday Night LT 0.10
Monday 0.50
Monday Night 0.25
Tuesday LT 0.10
Crystal Mt Precipitation (in)
Sunday Night LT 0.25
Monday 0.25 - 0.50
Monday Night LT 0.10
Tuesday 0
Paradise Precipitation (in)
Sunday Night 0.25
Monday 0.75
Monday Night 0.25
Tuesday LT 0.10
White Pass Precipitation (in)
Sunday Night 0.25 - 0.50
Monday 0.50 - 0.75
Monday Night LT 0.25
Tuesday 0
Washington Pass Precipitation (in)
Sunday Night 0
Monday LT 0.10
Monday Night LT 0.10
Tuesday 0
Mission Ridge Precipitation (in)
Sunday Night LT 0.10
Monday LT 0.25
Monday Night LT 0.10
Tuesday 0
Salmon la Sac - Gallagher Head Precipitation (in)
Sunday Night LT 0.10
Monday 0.25 - 0.50
Monday Night LT 0.25
Tuesday 0
Tieton River - Darland Mt. Precipitation (in)
Sunday Night 0.25 - 0.50
Monday 0.50
Monday Night LT 0.10
Tuesday 0
Mt Hood Meadows Precipitation (in)
Sunday Night 0.75
Monday 0.75
Monday Night LT 0.25
Tuesday 0
Timberline Precipitation (in)
Sunday Night 0.75
Monday 0.75
Monday Night 0.25
Tuesday 0

Issued: 2:07 PM PST Sunday, December 19, 2021

Snow Level (ft)

Sunday Evening* Sunday Night* Monday Morning* Monday Afternoon* Monday Evening* Monday Night* Tuesday Morning* Tuesday Afternoon*
Olympics 2000' 1500' 500' 1500' 2000' 3500' 5000' 5000'
West North 500' 500' 500' 1000' 1000' 1000' 2500' 4000'
West Central 1500' 1000' 0 1500' 2000' 2500' 5000' 5000'
West South 1000' 1000' 1000' 2500' 3500' 5000' 6000' 5500'
Stevens Pass 1000' 0 0 1000' 1500' 2000' 3500' 4000'
Snoqualmie Pass 1500' 0 500' 1500' 2000' 3000' 4000' 4000'
East North 500' 0 0 1000' 500' 1000' 2500' 4000'
East Central 500' 0 0 1000' 1000' 1500' 3000' 3500'
East South 1500' 1000' 1000' 2000' 3500' 5000' 5500' 6500'
Mt. Hood 2500' 2000' 2500' 3500' 5000' 6000' 5000' 6000'
Olympics Elevation
Sunday Evening* 2000'
Sunday Night* 1500'
Monday Morning* 500'
Monday Afternoon* 1500'
Monday Evening* 2000'
Monday Night* 3500'
Tuesday Morning* 5000'
Tuesday Afternoon* 5000'
West North Elevation
Sunday Evening* 500'
Sunday Night* 500'
Monday Morning* 500'
Monday Afternoon* 1000'
Monday Evening* 1000'
Monday Night* 1000'
Tuesday Morning* 2500'
Tuesday Afternoon* 4000'
West Central Elevation
Sunday Evening* 1500'
Sunday Night* 1000'
Monday Morning* 0'
Monday Afternoon* 1500'
Monday Evening* 2000'
Monday Night* 2500'
Tuesday Morning* 5000'
Tuesday Afternoon* 5000'
West South Elevation
Sunday Evening* 1000'
Sunday Night* 1000'
Monday Morning* 1000'
Monday Afternoon* 2500'
Monday Evening* 3500'
Monday Night* 5000'
Tuesday Morning* 6000'
Tuesday Afternoon* 5500'
Stevens Pass Elevation
Sunday Evening* 1000'
Sunday Night* 0'
Monday Morning* 0'
Monday Afternoon* 1000'
Monday Evening* 1500'
Monday Night* 2000'
Tuesday Morning* 3500'
Tuesday Afternoon* 4000'
Snoqualmie Pass Elevation
Sunday Evening* 1500'
Sunday Night* 0'
Monday Morning* 500'
Monday Afternoon* 1500'
Monday Evening* 2000'
Monday Night* 3000'
Tuesday Morning* 4000'
Tuesday Afternoon* 4000'
East North Elevation
Sunday Evening* 500'
Sunday Night* 0'
Monday Morning* 0'
Monday Afternoon* 1000'
Monday Evening* 500'
Monday Night* 1000'
Tuesday Morning* 2500'
Tuesday Afternoon* 4000'
East Central Elevation
Sunday Evening* 500'
Sunday Night* 0'
Monday Morning* 0'
Monday Afternoon* 1000'
Monday Evening* 1000'
Monday Night* 1500'
Tuesday Morning* 3000'
Tuesday Afternoon* 3500'
East South Elevation
Sunday Evening* 1500'
Sunday Night* 1000'
Monday Morning* 1000'
Monday Afternoon* 2000'
Monday Evening* 3500'
Monday Night* 5000'
Tuesday Morning* 5500'
Tuesday Afternoon* 6500'
Mt. Hood Elevation
Sunday Evening* 2500'
Sunday Night* 2000'
Monday Morning* 2500'
Monday Afternoon* 3500'
Monday Evening* 5000'
Monday Night* 6000'
Tuesday Morning* 5000'
Tuesday Afternoon* 6000'

Issued: 2:07 PM PST Sunday, December 19, 2021

5000' Temperatures (°F)

Sunday Night Monday
Max / Min Max / Min
Olympics 18 / 14 30 / 17
West North 17 / 15 26 / 17
West Central 18 / 17 27 / 17
West South 23 / 17 31 / 23
Stevens Pass 15 / 14 24 / 15
Snoqualmie Pass 19 / 16 26 / 19
East North 13 / 11 20 / 11
East Central 17 / 14 24 / 17
East South 19 / 16 31 / 19
Mt. Hood 29 / 25 35 / 29
Olympics 5000' Temperature Forecast
(Max / Min)
Sunday Night 18 / 14
Monday 30 / 17
West North 5000' Temperature Forecast
(Max / Min)
Sunday Night 17 / 15
Monday 26 / 17
West Central 5000' Temperature Forecast
(Max / Min)
Sunday Night 18 / 17
Monday 27 / 17
West South 5000' Temperature Forecast
(Max / Min)
Sunday Night 23 / 17
Monday 31 / 23
Stevens Pass 5000' Temperature Forecast
(Max / Min)
Sunday Night 15 / 14
Monday 24 / 15
Snoqualmie Pass 5000' Temperature Forecast
(Max / Min)
Sunday Night 19 / 16
Monday 26 / 19
East North 5000' Temperature Forecast
(Max / Min)
Sunday Night 13 / 11
Monday 20 / 11
East Central 5000' Temperature Forecast
(Max / Min)
Sunday Night 17 / 14
Monday 24 / 17
East South 5000' Temperature Forecast
(Max / Min)
Sunday Night 19 / 16
Monday 31 / 19
Mt. Hood 5000' Temperature Forecast
(Max / Min)
Sunday Night 29 / 25
Monday 35 / 29

Issued: 2:07 PM PST Sunday, December 19, 2021

Ridgeline Winds (mph)

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

Issued: 2:07 PM PST Sunday, December 19, 2021

Extended Weather Synopsis

The extended forecast starts mild, but should quickly turn snowy. A low sliding down the Alaska Panhandle Tuesday night will bring increasing westerly flow and mountain-induced precipitation to the region. Snow levels start relatively high around 4000 ft. The low digs southward with a trough axis offshore bringing SW winds and  moderate to possibly heavy rain and snow on Wednesday and Wednesday night as temperatures continue to cool. A strong temperature gradient brings W winds and additional cooling as the trough moves onshore Thursday, bringing additional moderate to heavy snowfall.

Extended Snow Level (ft)

Tuesday Night* Wednesday * Wednesday Night* Thursday *
West North 4000' 3000' 2500' 2000'
Snoqualmie Pass 4000' 3000' 2500' 2000'
Mt. Hood 4000' 3500' 3500' 3000'
West North Elevation
Tuesday Night* 4000'
Wednesday * 3000'
Wednesday Night* 2500'
Thursday * 2000'
Snoqualmie Pass Elevation
Tuesday Night* 4000'
Wednesday * 3000'
Wednesday Night* 2500'
Thursday * 2000'
Mt. Hood Elevation
Tuesday Night* 4000'
Wednesday * 3500'
Wednesday Night* 3500'
Thursday * 3000'

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

Previous forecast from Dec 19, 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’.