Issued: 2:15 PM PST Saturday, December 18, 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 strong front moving from NW to SE across much of Washington State will focus the frontal rain/snow on the southern Washington Cascades and increasingly Mt. Hood on Saturday night. This rain and snow should be heavy at times and comes with a cooling trend, allowing snow to return to ski area bases such as Timberline and Mt. Hood Meadows. Expect 5-10" of heavy, dense snowfall overnight around Mt. Hood with decreasing moderate winds. Behind the cold front, cooler air moves with some moderate to heavy convergence in the Mountain Loop area during the early evening. Drier air should move quickly and most areas from Snoqualmie Pass can expect limited snow accumulation in areas north or south of the convergence.

The front stalls over northern Oregon on Sunday due to closed low off the California coast. This keeps the action centered on Mt. Hood. A wave along the front should allow for a reversal back northward as a warm front. This brings increasing light snowfall into the southern Washington Cascades south of I90.

The warm front continues lifting northward Sunday night and Monday with the heaviest precipitation shifting to the central Washington Cascades and expanding north to the Canadian border by Monday afternoon. Cool air in place combined with low-level easterly flow means this will be a primarily snow event. The east slopes stand to pick up appreciable snow as do the southern Cascade Volcanoes as flow turns increasingly southerly. Mt. Hood should be the winner with 1-2 ft of snow Saturday night through Monday.

 

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
Saturday Night Mostly cloudy with a chance of snow showers. Colder.
Sunday Partly cloudy.
Saturday Night Light snow or modest convergence tapering to snow flurries overnight.
Sunday Partly cloudy.
Saturday Night Heavy snowfall possible in convergence banding during the early evening, then light snow showers at times.
Sunday Partly cloudy.
Saturday Night Decreasing light snow in the evening, then becoming mostly cloudy.
Sunday Cloudy with light snow developing in the afternoon for the Mt Rainier area. Light snow developing earlier near Mt. St Helens and Mt. Adams, increasing to moderate in the afternoon.
Saturday Night Light snow showers with a chance of convergence in the early evening, then becoming mostly cloudy. Cooling. Decreasing moderate winds early, then becoming light or variable at the Pass.
Sunday Partly cloudy in the morning with high clouds increasing in the afternoon. Increasing E winds becoming moderate late in the day at the Pass.
Saturday Night Light rain and snow in the early evening then becoming cloudy with a chance of flurries. Cooling. Decreasing moderate winds early, then becoming light or variable at the Pass.
Sunday Partly cloudy in the morning with high clouds increasing in the afternoon. Increasing E winds becoming moderate late in the day at the Pass.
Saturday Night Light snow showers near the Cascade Crest. Elsewhere, clearing skies.
Sunday Partly cloudy.
Saturday Night Light snow (or low elevation rain) in the early evening, then partial clearing. Strong ridgeline wind gusts in the evening, then decreasing.
Sunday Increasing clouds with a chance of light snow developing in the southern part late in the day.
Saturday Night Light to moderate rain and snow decreasing and ending from north to south.
Sunday Increasing light snow developing from south to north (possibly moderate at times late in the day).
Saturday Night Moderate to heavy snow. Strong ridgeline winds decreasing into the moderate range.
Sunday Moderate to heavy rain and snow.

Issued: 2:15 PM PST Saturday, December 18, 2021

Precipitation (in)

Saturday Night Sunday Sunday Night Monday
4 pm - 4 am 4 am - 4 pm 4 pm - 4 am 4 am - 4 pm
Hurricane Ridge LT 0.10 0 0 0.50
Mt Baker Ski Area LT 0.25 0 0 LT 0.25
Mt. Loop - Barlow Pass 0.25 - 0.50 0 LT 0.10 0.25 - 0.50
Stevens Pass 0.25 0 LT 0.10 0.25 - 0.50
Snoqualmie Pass 0.25 0 LT 0.10 0.50 - 0.75
Crystal Mt 0.25 LT 0.10 0.25 0.50
Paradise 0.25 LT 0.10 0.50 0.75 -1.00
White Pass 0.25 - 0.50 LT 0.25 0.50 0.75
Washington Pass LT 0.10 0 0 0.25 - 0.50
Mission Ridge LT 0.10 LT 0.10 LT 0.10 LT 0.25
Salmon la Sac - Gallagher Head LT 0.25 LT 0.10 LT 0.10 0.50
Tieton River - Darland Mt. 0.25 - 0.50 LT 0.25 0.25 - 0.50 0.50 - 0.75
Mt Hood Meadows 0.75 -1.00 0.75 0.75 0.50
Timberline 0.75 -1.00 0.75 -1.00 0.75 -1.00 0.50 - 0.75
Hurricane Ridge Precipitation (in)
Saturday Night LT 0.10
Sunday 0
Sunday Night 0
Monday 0.50
Mt Baker Ski Area Precipitation (in)
Saturday Night LT 0.25
Sunday 0
Sunday Night 0
Monday LT 0.25
Mt. Loop - Barlow Pass Precipitation (in)
Saturday Night 0.25 - 0.50
Sunday 0
Sunday Night LT 0.10
Monday 0.25 - 0.50
Stevens Pass Precipitation (in)
Saturday Night 0.25
Sunday 0
Sunday Night LT 0.10
Monday 0.25 - 0.50
Snoqualmie Pass Precipitation (in)
Saturday Night 0.25
Sunday 0
Sunday Night LT 0.10
Monday 0.50 - 0.75
Crystal Mt Precipitation (in)
Saturday Night 0.25
Sunday LT 0.10
Sunday Night 0.25
Monday 0.50
Paradise Precipitation (in)
Saturday Night 0.25
Sunday LT 0.10
Sunday Night 0.50
Monday 0.75 -1.00
White Pass Precipitation (in)
Saturday Night 0.25 - 0.50
Sunday LT 0.25
Sunday Night 0.50
Monday 0.75
Washington Pass Precipitation (in)
Saturday Night LT 0.10
Sunday 0
Sunday Night 0
Monday 0.25 - 0.50
Mission Ridge Precipitation (in)
Saturday Night LT 0.10
Sunday LT 0.10
Sunday Night LT 0.10
Monday LT 0.25
Salmon la Sac - Gallagher Head Precipitation (in)
Saturday Night LT 0.25
Sunday LT 0.10
Sunday Night LT 0.10
Monday 0.50
Tieton River - Darland Mt. Precipitation (in)
Saturday Night 0.25 - 0.50
Sunday LT 0.25
Sunday Night 0.25 - 0.50
Monday 0.50 - 0.75
Mt Hood Meadows Precipitation (in)
Saturday Night 0.75 -1.00
Sunday 0.75
Sunday Night 0.75
Monday 0.50
Timberline Precipitation (in)
Saturday Night 0.75 -1.00
Sunday 0.75 -1.00
Sunday Night 0.75 -1.00
Monday 0.50 - 0.75

Issued: 2:15 PM PST Saturday, December 18, 2021

Snow Level (ft)

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

Issued: 2:15 PM PST Saturday, December 18, 2021

5000' Temperatures (°F)

Saturday Night Sunday
Max / Min Max / Min
Olympics 21 / 16 21 / 15
West North 22 / 18 19 / 14
West Central 25 / 20 21 / 15
West South 26 / 16 26 / 15
Stevens Pass 25 / 18 23 / 16
Snoqualmie Pass 25 / 17 22 / 16
East North 23 / 16 19 / 12
East Central 25 / 17 22 / 14
East South 27 / 19 25 / 16
Mt. Hood 35 / 25 28 / 25
Olympics 5000' Temperature Forecast
(Max / Min)
Saturday Night 21 / 16
Sunday 21 / 15
West North 5000' Temperature Forecast
(Max / Min)
Saturday Night 22 / 18
Sunday 19 / 14
West Central 5000' Temperature Forecast
(Max / Min)
Saturday Night 25 / 20
Sunday 21 / 15
West South 5000' Temperature Forecast
(Max / Min)
Saturday Night 26 / 16
Sunday 26 / 15
Stevens Pass 5000' Temperature Forecast
(Max / Min)
Saturday Night 25 / 18
Sunday 23 / 16
Snoqualmie Pass 5000' Temperature Forecast
(Max / Min)
Saturday Night 25 / 17
Sunday 22 / 16
East North 5000' Temperature Forecast
(Max / Min)
Saturday Night 23 / 16
Sunday 19 / 12
East Central 5000' Temperature Forecast
(Max / Min)
Saturday Night 25 / 17
Sunday 22 / 14
East South 5000' Temperature Forecast
(Max / Min)
Saturday Night 27 / 19
Sunday 25 / 16
Mt. Hood 5000' Temperature Forecast
(Max / Min)
Saturday Night 35 / 25
Sunday 28 / 25

Issued: 2:15 PM PST Saturday, December 18, 2021

Ridgeline Winds (mph)

Saturday Evening Saturday Night Sunday Morning Sunday Afternoon
Olympics WSW 10-20 WSW 5-15 NE 0-10 ENE 0-10
West North WSW 15-25 SW 5-15 NE 0-10 ENE 0-10
West Central WSW 10-20 WSW 10-20 NW 0-10 ESE 5-15
West South W 10-20 WNW 5-15 N 0-10 ESE 0-10
Stevens Pass W 15-25 W 10-20 WNW 0-10 ESE 0-10
Snoqualmie Pass W 15-25 WNW 15-25 NW 5-15 ESE 5-15
East North W 20-30 W 15-25 WNW 0-10 SE 0-10
East Central W 20-30 WNW 15-25 WNW 5-15 SE 0-10
East South W 20-30 WNW 5-15 E 0-10 ESE 0-10
Mt. Hood WSW 25-35 WSW 15-25 SW 10-20 SW 15-25
Olympics Ridgeline Winds (mph)
Saturday Evening WSW 10-20
Saturday Night WSW 5-15
Sunday Morning NE 0-10
Sunday Afternoon ENE 0-10
West North Ridgeline Winds (mph)
Saturday Evening WSW 15-25
Saturday Night SW 5-15
Sunday Morning NE 0-10
Sunday Afternoon ENE 0-10
West Central Ridgeline Winds (mph)
Saturday Evening WSW 10-20
Saturday Night WSW 10-20
Sunday Morning NW 0-10
Sunday Afternoon ESE 5-15
West South Ridgeline Winds (mph)
Saturday Evening W 10-20
Saturday Night WNW 5-15
Sunday Morning N 0-10
Sunday Afternoon ESE 0-10
Stevens Pass Ridgeline Winds (mph)
Saturday Evening W 15-25
Saturday Night W 10-20
Sunday Morning WNW 0-10
Sunday Afternoon ESE 0-10
Snoqualmie Pass Ridgeline Winds (mph)
Saturday Evening W 15-25
Saturday Night WNW 15-25
Sunday Morning NW 5-15
Sunday Afternoon ESE 5-15
East North Ridgeline Winds (mph)
Saturday Evening W 20-30
Saturday Night W 15-25
Sunday Morning WNW 0-10
Sunday Afternoon SE 0-10
East Central Ridgeline Winds (mph)
Saturday Evening W 20-30
Saturday Night WNW 15-25
Sunday Morning WNW 5-15
Sunday Afternoon SE 0-10
East South Ridgeline Winds (mph)
Saturday Evening W 20-30
Saturday Night WNW 5-15
Sunday Morning E 0-10
Sunday Afternoon ESE 0-10
Mt. Hood Ridgeline Winds (mph)
Saturday Evening WSW 25-35
Saturday Night WSW 15-25
Sunday Morning SW 10-20
Sunday Afternoon SW 15-25

Issued: 2:15 PM PST Saturday, December 18, 2021

Extended Weather Synopsis

The warm front that lifted north across the region on Monday gets sheared apart a low pressure moves northward off the Oregon coast Monday night. This brings a temporary drying trend to the region with only a few light snow showers or sprinkles Monday night. Easterly flow allows cooler air to filter back into the region. Another band of moisture moves into the region Tuesday afternoon with light snowfall above approximately 3500 ft. Tuesday night into Wednesday, a trough dropping down the British Columbia coast, phases with the low spinning off the Oregon coast. This development should cool temperatures slightly and lift waves of moderate snowfall into the region.

Extended Snow Level (ft)

Monday Night* Tuesday * Tuesday Night* Wednesday *
West North 1000' 3500' 3000' 3000'
Snoqualmie Pass 3000' 3500' 2500' 3000'
Mt. Hood 3500' 3500' 3000' 3000'
West North Elevation
Monday Night* 1000'
Tuesday * 3500'
Tuesday Night* 3000'
Wednesday * 3000'
Snoqualmie Pass Elevation
Monday Night* 3000'
Tuesday * 3500'
Tuesday Night* 2500'
Wednesday * 3000'
Mt. Hood Elevation
Monday Night* 3500'
Tuesday * 3500'
Tuesday Night* 3000'
Wednesday * 3000'

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

Previous forecast from Dec 18, 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’.