Issued: 7:05 AM PST Friday, December 17, 2021
by Dennis D'Amico

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

Weather Synopsis

High clouds will stream over the region today in advance of an approaching frontal system with overcast skies for all areas by mid-day.  A low pressure system will deepen as it curls towards the central British Columbia coast tonight.  Warm frontal moisture will spread inland from the coast overnight, reaching as far south as Mt Hood. As the main frontal boundary sets up into southern B.C., the axis of the heaviest precipitation will shift towards the Canadian border Saturday morning.  Forecast models are still struggling with just how much precipitation falls from Stevens Pass and southward during the day on Saturday.  On top of a wide range of precipitation total outcomes, mild air blowing in on strong SW winds will battle with cold air entrenched over the Cascades and especially east of the Cascade Crest on Saturday.  

Currently, it seems likely there will be a wintry mix including freezing rain for places like Snoqualmie Pass and White Pass from mid-morning Saturday through early afternoon before a switch to rain.  Stevens Pass may see a wintry mix late in the day. The rain line should push up to 5000' for the southern Cascades and even higher for Mt Hood on Saturday albeit with lighter precipitation.  Along the east slopes of the Cascades, areas north of I-90 should hold onto snow for most of the day, with a potential wintry mix between highway 2 and I-90 later Saturday afternoon. The mountains from Lake Chelan and northward will likely stick as snow all day. Alpine winds will be extreme out of the SW later Saturday as well from the central Cascades and southward.  

All in all this is a messy system with a fair amount of uncertainty with precipitation totals to kick off the weekend. 

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
Friday Becoming overcast with increasing high clouds this morning.
Friday Night Light rain and snow developing and becoming moderate after midnight. Strong winds developing overnight.
Friday Becoming overcast with increasing high clouds this morning.
Friday Night Light rain and snow developing and becoming moderate after midnight. Strong winds developing overnight.
Friday Becoming overcast with increasing high clouds this morning.
Friday Night Light rain and snow developing and becoming moderate after midnight. Strong winds developing overnight.
Friday Becoming overcast with increasing high clouds this morning.
Friday Night Cloudy, then light rain and snow developing after midnight. Strong winds developing late.
Friday Becoming overcast with increasing high clouds this morning.
Friday Night Cloudy, then light rain and snow developing after midnight. Light east winds at Pass level becoming moderate after midnight.
Friday Becoming overcast with increasing high clouds this morning.
Friday Night Cloudy, then light rain and snow developing after midnight. Light east winds at Pass level becoming moderate after midnight.
Friday Becoming overcast with increasing high clouds this morning.
Friday Night Cloudy, then light rain and snow developing after midnight.
Friday Becoming overcast with increasing high clouds this morning.
Friday Night Cloudy, then light rain and snow developing after midnight. Strong winds developing late.
Friday Becoming overcast with increasing high clouds this morning.
Friday Night Cloudy, then light rain and snow developing after midnight.
Friday Becoming overcast with increasing high clouds this morning.
Friday Night Cloudy, then light rain and snow developing after midnight.

Precipitation (in)

Friday Friday Night Saturday
4 am - 4 pm 4 pm - 4 am 4 am - 4 pm
Hurricane Ridge 0 0.25 - 0.50 1.00 - 1.50
Mt Baker Ski Area 0 0.25 - 0.50 1.00 - 1.50
Mt. Loop - Barlow Pass 0 0.25 1.50
Stevens Pass 0 LT 0.25 0.75
Snoqualmie Pass 0 LT 0.25 0.75 -1.00
Crystal Mt 0 LT 0.10 0.25 - 0.50
Paradise 0 LT 0.25 0.75
White Pass 0 LT 0.10 0.25 - 0.50
Washington Pass 0 LT 0.25 1.00
Mission Ridge 0 LT 0.10 LT 0.25
Salmon la Sac - Gallagher Head 0 LT 0.25 0.50
Tieton River - Darland Mt. 0 LT 0.10 LT 0.25
Mt Hood Meadows 0 LT 0.10 0.25
Timberline 0 LT 0.10 0.25 - 0.50
Hurricane Ridge Precipitation (in)
Friday 0
Friday Night 0.25 - 0.50
Saturday 1.00 - 1.50
Mt Baker Ski Area Precipitation (in)
Friday 0
Friday Night 0.25 - 0.50
Saturday 1.00 - 1.50
Mt. Loop - Barlow Pass Precipitation (in)
Friday 0
Friday Night 0.25
Saturday 1.50
Stevens Pass Precipitation (in)
Friday 0
Friday Night LT 0.25
Saturday 0.75
Snoqualmie Pass Precipitation (in)
Friday 0
Friday Night LT 0.25
Saturday 0.75 -1.00
Crystal Mt Precipitation (in)
Friday 0
Friday Night LT 0.10
Saturday 0.25 - 0.50
Paradise Precipitation (in)
Friday 0
Friday Night LT 0.25
Saturday 0.75
White Pass Precipitation (in)
Friday 0
Friday Night LT 0.10
Saturday 0.25 - 0.50
Washington Pass Precipitation (in)
Friday 0
Friday Night LT 0.25
Saturday 1.00
Mission Ridge Precipitation (in)
Friday 0
Friday Night LT 0.10
Saturday LT 0.25
Salmon la Sac - Gallagher Head Precipitation (in)
Friday 0
Friday Night LT 0.25
Saturday 0.50
Tieton River - Darland Mt. Precipitation (in)
Friday 0
Friday Night LT 0.10
Saturday LT 0.25
Mt Hood Meadows Precipitation (in)
Friday 0
Friday Night LT 0.10
Saturday 0.25
Timberline Precipitation (in)
Friday 0
Friday Night LT 0.10
Saturday 0.25 - 0.50

Snow Level (ft)

Friday Morning Friday Afternoon* Friday Evening* Friday Night* Saturday Morning* Saturday Afternoon
Olympics 1500' 2500' 2000' 2500' 5000' 4000'
West North 500' 1500' 1000' 1500' 2500' 3500'
West Central 500' 2000' 1000' 1500' 3000' 4500'
West South 500' 2500' 1500' 2000' 3500' 5000'
Stevens Pass 500' 1500' 500' 1000' 1500' 4000'
Snoqualmie Pass 500' 2000' 1000' 1500' 3000' 5000'
East North 0 1000' 0 0 1000' 1000'
East Central 0 1000' 0 0 1000' 1500'
East South 500' 2000' 1000' 1500' 2500' 5000'
Mt. Hood 2500' 3500' 3000' 4000' 6500' 7000'
Olympics Elevation
Friday Morning 1500'
Friday Afternoon* 2500'
Friday Evening* 2000'
Friday Night* 2500'
Saturday Morning* 5000'
Saturday Afternoon 4000'
West North Elevation
Friday Morning 500'
Friday Afternoon* 1500'
Friday Evening* 1000'
Friday Night* 1500'
Saturday Morning* 2500'
Saturday Afternoon 3500'
West Central Elevation
Friday Morning 500'
Friday Afternoon* 2000'
Friday Evening* 1000'
Friday Night* 1500'
Saturday Morning* 3000'
Saturday Afternoon 4500'
West South Elevation
Friday Morning 500'
Friday Afternoon* 2500'
Friday Evening* 1500'
Friday Night* 2000'
Saturday Morning* 3500'
Saturday Afternoon 5000'
Stevens Pass Elevation
Friday Morning 500'
Friday Afternoon* 1500'
Friday Evening* 500'
Friday Night* 1000'
Saturday Morning* 1500'
Saturday Afternoon 4000'
Snoqualmie Pass Elevation
Friday Morning 500'
Friday Afternoon* 2000'
Friday Evening* 1000'
Friday Night* 1500'
Saturday Morning* 3000'
Saturday Afternoon 5000'
East North Elevation
Friday Morning 0'
Friday Afternoon* 1000'
Friday Evening* 0'
Friday Night* 0'
Saturday Morning* 1000'
Saturday Afternoon 1000'
East Central Elevation
Friday Morning 0'
Friday Afternoon* 1000'
Friday Evening* 0'
Friday Night* 0'
Saturday Morning* 1000'
Saturday Afternoon 1500'
East South Elevation
Friday Morning 500'
Friday Afternoon* 2000'
Friday Evening* 1000'
Friday Night* 1500'
Saturday Morning* 2500'
Saturday Afternoon 5000'
Mt. Hood Elevation
Friday Morning 2500'
Friday Afternoon* 3500'
Friday Evening* 3000'
Friday Night* 4000'
Saturday Morning* 6500'
Saturday Afternoon 7000'

5000' Temperatures (°F)

Friday Friday Night
Max / Min Max / Min
Olympics 25 / 18 34 / 25
West North 23 / 14 29 / 21
West Central 24 / 16 29 / 21
West South 27 / 14 30 / 23
Stevens Pass 25 / 17 23 / 18
Snoqualmie Pass 24 / 15 25 / 18
East North 19 / 10 17 / 13
East Central 24 / 15 22 / 17
East South 28 / 14 28 / 22
Mt. Hood 30 / 22 31 / 24
Olympics 5000' Temperature Forecast
(Max / Min)
Friday 25 / 18
Friday Night 34 / 25
West North 5000' Temperature Forecast
(Max / Min)
Friday 23 / 14
Friday Night 29 / 21
West Central 5000' Temperature Forecast
(Max / Min)
Friday 24 / 16
Friday Night 29 / 21
West South 5000' Temperature Forecast
(Max / Min)
Friday 27 / 14
Friday Night 30 / 23
Stevens Pass 5000' Temperature Forecast
(Max / Min)
Friday 25 / 17
Friday Night 23 / 18
Snoqualmie Pass 5000' Temperature Forecast
(Max / Min)
Friday 24 / 15
Friday Night 25 / 18
East North 5000' Temperature Forecast
(Max / Min)
Friday 19 / 10
Friday Night 17 / 13
East Central 5000' Temperature Forecast
(Max / Min)
Friday 24 / 15
Friday Night 22 / 17
East South 5000' Temperature Forecast
(Max / Min)
Friday 28 / 14
Friday Night 28 / 22
Mt. Hood 5000' Temperature Forecast
(Max / Min)
Friday 30 / 22
Friday Night 31 / 24

Ridgeline Winds (mph)

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

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

Previous forecast from Dec 16, 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’.