After a benign day with increasing high clouds, a major winter storm is on tap for the weekend. A low pressure system curling towards the central British Columbia coast will spread warm frontal moisture inland tonight. Forecast models have trended heavier with this first wave of moisture overnight. With cold air entrenched in place, snow levels will be slow to rise over the Cascades tonight. The warm frontal precipitation will lift northwards Saturday morning, potentially relaxing precipitation rates south of Snoqualmie Pass during the morning hours. The trailing cold front will slowly sag south Saturday afternoon, bringing extreme SW alpine winds and heavy precipitation to most areas. There's still wild divergence in precipitation amounts from Stevens Pass and southward regarding how heavy precipitation is during the day on Saturday. On top of that, warm air overrunning cold air entrenched in the Cascades opens the door for a wintry mix, including freezing rain, in some locations. The west-side south of Hwy 2 and Snoqualmie and White Passes may a mix late morning while the east slopes of the Cascades near and south of I-90 may see a wintry mix in the afternoon to early evening Saturday. The north Cascades and likely Stevens Pass will stay snow with a much more muted warming trend. Mt Hood will be on the warm side for this system with 6000-7000' snow levels Saturday.
The front will slowly sag south Saturday evening and become a stationary feature across the Columbia River gap by early Sunday morning. Showers should quickly end from north to south overnight Saturday for the Washington Cascades and Olympics as snow levels fall behind the front. The frontal boundary may stay draped over the Washington/Oregon border on Sunday, where locally moderate to heavy precipitation is possible for Mt. Hood. Much drier air will filter into closer to the Canadain border on Sunday.
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
Night
Light rain and snow developing and becoming moderate after midnight. Strong winds developing overnight.
Saturday
Heavy rain and snow in the morning becoming scattered rain and snow showers in the afternoon. Strong to extreme ridgeline winds in the morning, easing in the afternoon. Cooling trend in the afternoon.
Friday
Night
Light rain and snow developing and becoming moderate after midnight. Strong winds developing overnight.
Saturday
Heavy rain and snow in the morning becoming scattered rain and snow showers late in the afternoon. Strong to extreme ridgeline winds in the morning, easing in the afternoon. Cooling trend late.
Friday
Night
Light rain and snow developing and becoming moderate after midnight. Strong winds developing overnight.
Saturday
Heavy rain and snow. Strong to extreme ridgeline winds.
Friday
Night
Cloudy, then light rain and snow developing after midnight. Strong winds developing late.
Saturday
Light rain and snow becoming moderate to locally heavy in the afternoon. Strong to extreme ridgeline winds developing during the day. Warming trend.
Friday
Night
Cloudy, then light rain and snow developing after midnight and increasing late. Light east winds at Pass level becoming moderate after midnight.
Saturday
Moderate to occasionally heavy rain and snow. Strong to extreme ridgeline west winds developing during the day. Moderate east winds at Pass level becoming west in the afternoon. Slight chance of freezing rain late. Slight warming trend.
Friday
Night
Cloudy, then light rain and snow developing after midnight and increasing late. Light east winds at Pass level becoming moderate after midnight.
Saturday
Light to moderate rain and snow becoming heavy in the afternoon. Strong to extreme ridgeline west winds developing during the day. Moderate east winds at Pass level becoming west in the afternoon. Chance for freezing rain from mid-morning through early afternoon. Warming trend.
Friday
Night
Cloudy, then light rain and snow developing after midnight and increasing late.
Saturday
Moderate to occasionally heavy snow. Strong ridgeline winds.
Friday
Night
Cloudy, then light rain and snow developing after midnight. Strong winds developing late.
Saturday
Light to moderate snow increasing in the afternoon. Chance of freezing rain late in the day. Strong to extreme ridgeline winds developing. Slight warming trend.
Friday
Night
Cloudy, then light rain and snow developing after midnight.
Saturday
Light to occasionally moderate snow increasing in the afternoon. Chance of freezing rain in the afternoon.Strong to extreme ridgeline winds developing. Slight warming trend.
Friday
Night
Cloudy, then light rain and snow developing after midnight.
Saturday
Light rain and snow increasing in the afternoon. Strong to extreme winds, especially in the alpine. Warming trend.
Issued: 2:13 PM PST Friday, December 17, 2021
Precipitation (in)
Friday Night
Saturday
Saturday Night
Sunday
4 pm - 4 am
4 am - 4 pm
4 pm - 4 am
4 am - 4 pm
Hurricane Ridge
0.50 - 0.75
1.50
LT 0.10
0
Mt Baker Ski Area
0.75
1.50 - 2.00
LT 0.25
0
Mt. Loop - Barlow Pass
0.50
2.00
0.50
0
Stevens Pass
0.25 - 0.50
1.00 - 1.50
0.50
0
Snoqualmie Pass
0.25 - 0.50
1.00
0.75
0
Crystal Mt
LT 0.25
0.50 - 0.75
0.50
LT 0.10
Paradise
0.50
1.00 - 1.50
0.75
LT 0.25
White Pass
0.25
0.50
0.75 -1.00
LT 0.25
Washington Pass
0.25
1.00 - 1.50
0.25 - 0.50
0
Mission Ridge
LT 0.25
0.25
LT 0.25
LT 0.10
Salmon la Sac - Gallagher Head
0.25
0.75
0.25 - 0.50
0
Tieton River - Darland Mt.
LT 0.25
0.25 - 0.50
0.50
LT 0.25
Mt Hood Meadows
LT 0.25
0.50
1.00
1.00
Timberline
0.25
0.50
1.00 - 1.50
1.00
Hurricane Ridge
Precipitation (in)
Friday Night
0.50 - 0.75
Saturday
1.50
Saturday Night
LT 0.10
Sunday
0
Mt Baker Ski Area
Precipitation (in)
Friday Night
0.75
Saturday
1.50 - 2.00
Saturday Night
LT 0.25
Sunday
0
Mt. Loop - Barlow Pass
Precipitation (in)
Friday Night
0.50
Saturday
2.00
Saturday Night
0.50
Sunday
0
Stevens Pass
Precipitation (in)
Friday Night
0.25 - 0.50
Saturday
1.00 - 1.50
Saturday Night
0.50
Sunday
0
Snoqualmie Pass
Precipitation (in)
Friday Night
0.25 - 0.50
Saturday
1.00
Saturday Night
0.75
Sunday
0
Crystal Mt
Precipitation (in)
Friday Night
LT 0.25
Saturday
0.50 - 0.75
Saturday Night
0.50
Sunday
LT 0.10
Paradise
Precipitation (in)
Friday Night
0.50
Saturday
1.00 - 1.50
Saturday Night
0.75
Sunday
LT 0.25
White Pass
Precipitation (in)
Friday Night
0.25
Saturday
0.50
Saturday Night
0.75 -1.00
Sunday
LT 0.25
Washington Pass
Precipitation (in)
Friday Night
0.25
Saturday
1.00 - 1.50
Saturday Night
0.25 - 0.50
Sunday
0
Mission Ridge
Precipitation (in)
Friday Night
LT 0.25
Saturday
0.25
Saturday Night
LT 0.25
Sunday
LT 0.10
Salmon la Sac - Gallagher Head
Precipitation (in)
Friday Night
0.25
Saturday
0.75
Saturday Night
0.25 - 0.50
Sunday
0
Tieton River - Darland Mt.
Precipitation (in)
Friday Night
LT 0.25
Saturday
0.25 - 0.50
Saturday Night
0.50
Sunday
LT 0.25
Mt Hood Meadows
Precipitation (in)
Friday Night
LT 0.25
Saturday
0.50
Saturday Night
1.00
Sunday
1.00
Timberline
Precipitation (in)
Friday Night
0.25
Saturday
0.50
Saturday Night
1.00 - 1.50
Sunday
1.00
Issued: 2:13 PM PST Friday, December 17, 2021
Snow Level (ft)
Friday
Evening*
Friday
Night*
Saturday
Morning*
Saturday
Afternoon
Saturday
Evening
Saturday
Night
Sunday
Morning
Sunday
Afternoon
Olympics
2000'
2500'
5000'
3500'
2000'
1500'
1000'
2000'
West North
1000'
1500'
2000'
3500'
2000'
1000'
500'
1500'
West Central
1000'
1500'
3000'
4500'
2500'
1000'
1000'
2000'
West South
1500'
2000'
3500'
5000'
3000'
2000'
1500'
2500'
Stevens Pass
500'
1000'
1500'
4000'
2500'
1000'
500'
2000'
Snoqualmie Pass
1000'
1500'
3000'
4500'
3000'
1500'
1000'
2500'
East North
0
0
1000'
1000'
1500'
0
0
2000'
East Central
0
0
1000'
1500'
2000'
1000'
500'
2000'
East South
1000'
1500'
2500'
5000'
3500'
2000'
2500'
2500'
Mt. Hood
3000'
2500'
6500'
7000'
4500'
4500'
4500'
4000'
Olympics
Elevation
Friday
Evening*
2000'
Friday
Night*
2500'
Saturday
Morning*
5000'
Saturday
Afternoon
3500'
Saturday
Evening
2000'
Saturday
Night
1500'
Sunday
Morning
1000'
Sunday
Afternoon
2000'
West North
Elevation
Friday
Evening*
1000'
Friday
Night*
1500'
Saturday
Morning*
2000'
Saturday
Afternoon
3500'
Saturday
Evening
2000'
Saturday
Night
1000'
Sunday
Morning
500'
Sunday
Afternoon
1500'
West Central
Elevation
Friday
Evening*
1000'
Friday
Night*
1500'
Saturday
Morning*
3000'
Saturday
Afternoon
4500'
Saturday
Evening
2500'
Saturday
Night
1000'
Sunday
Morning
1000'
Sunday
Afternoon
2000'
West South
Elevation
Friday
Evening*
1500'
Friday
Night*
2000'
Saturday
Morning*
3500'
Saturday
Afternoon
5000'
Saturday
Evening
3000'
Saturday
Night
2000'
Sunday
Morning
1500'
Sunday
Afternoon
2500'
Stevens Pass
Elevation
Friday
Evening*
500'
Friday
Night*
1000'
Saturday
Morning*
1500'
Saturday
Afternoon
4000'
Saturday
Evening
2500'
Saturday
Night
1000'
Sunday
Morning
500'
Sunday
Afternoon
2000'
Snoqualmie Pass
Elevation
Friday
Evening*
1000'
Friday
Night*
1500'
Saturday
Morning*
3000'
Saturday
Afternoon
4500'
Saturday
Evening
3000'
Saturday
Night
1500'
Sunday
Morning
1000'
Sunday
Afternoon
2500'
East North
Elevation
Friday
Evening*
0'
Friday
Night*
0'
Saturday
Morning*
1000'
Saturday
Afternoon
1000'
Saturday
Evening
1500'
Saturday
Night
0'
Sunday
Morning
0'
Sunday
Afternoon
2000'
East Central
Elevation
Friday
Evening*
0'
Friday
Night*
0'
Saturday
Morning*
1000'
Saturday
Afternoon
1500'
Saturday
Evening
2000'
Saturday
Night
1000'
Sunday
Morning
500'
Sunday
Afternoon
2000'
East South
Elevation
Friday
Evening*
1000'
Friday
Night*
1500'
Saturday
Morning*
2500'
Saturday
Afternoon
5000'
Saturday
Evening
3500'
Saturday
Night
2000'
Sunday
Morning
2500'
Sunday
Afternoon
2500'
Mt. Hood
Elevation
Friday
Evening*
3000'
Friday
Night*
2500'
Saturday
Morning*
6500'
Saturday
Afternoon
7000'
Saturday
Evening
4500'
Saturday
Night
4500'
Sunday
Morning
4500'
Sunday
Afternoon
4000'
Issued: 2:13 PM PST Friday, December 17, 2021
5000' Temperatures (°F)
Friday
Night
Saturday
Max / Min
Max / Min
Olympics
33 / 24
33 / 25
West North
28 / 20
31 / 24
West Central
28 / 21
33 / 26
West South
30 / 23
33 / 28
Stevens Pass
25 / 19
33 / 25
Snoqualmie Pass
24 / 19
34 / 26
East North
17 / 13
27 / 18
East Central
22 / 19
33 / 23
East South
29 / 23
34 / 30
Mt. Hood
31 / 25
36 / 32
Olympics
5000' Temperature Forecast (Max / Min)
Friday
Night
33 / 24
Saturday
33 / 25
West North
5000' Temperature Forecast (Max / Min)
Friday
Night
28 / 20
Saturday
31 / 24
West Central
5000' Temperature Forecast (Max / Min)
Friday
Night
28 / 21
Saturday
33 / 26
West South
5000' Temperature Forecast (Max / Min)
Friday
Night
30 / 23
Saturday
33 / 28
Stevens Pass
5000' Temperature Forecast (Max / Min)
Friday
Night
25 / 19
Saturday
33 / 25
Snoqualmie Pass
5000' Temperature Forecast (Max / Min)
Friday
Night
24 / 19
Saturday
34 / 26
East North
5000' Temperature Forecast (Max / Min)
Friday
Night
17 / 13
Saturday
27 / 18
East Central
5000' Temperature Forecast (Max / Min)
Friday
Night
22 / 19
Saturday
33 / 23
East South
5000' Temperature Forecast (Max / Min)
Friday
Night
29 / 23
Saturday
34 / 30
Mt. Hood
5000' Temperature Forecast (Max / Min)
Friday
Night
31 / 25
Saturday
36 / 32
Issued: 2:13 PM PST Friday, December 17, 2021
Ridgeline Winds (mph)
Friday
Evening
Friday
Night
Saturday
Morning
Saturday
Afternoon
Olympics
S 10-20
SW 25-35
SW 35-50
WSW 15-25
West North
S 15-25
SSW 25-35
SSW 40-55
WSW 15-25
West Central
SW 10-20
SW 20-30
SW 40-55
WSW 25-35
West South
SW 10-20
SSW 20-30
SW 25-35
SW 40-55
Stevens Pass
SW 5-15
SSE 5-15
SW 25-35
SW 30-40
Snoqualmie Pass
SW 5-15
SSE 5-15
SW 25-35
SW 35-50
East North
SW 10-20
SW 10-20
SW 25-35
WSW 20-30
East Central
SW 5-15
SSW 15-25
SW 20-30
SW 40-55
East South
SSW 5-15
SW 10-20
WSW 25-35
WSW 40-55
Mt. Hood
SW 10-20
WSW 20-30
WSW 25-35
WSW 40-55
Olympics
Ridgeline Winds (mph)
Friday
Evening
S
10-20
Friday
Night
SW
25-35
Saturday
Morning
SW
35-50
Saturday
Afternoon
WSW
15-25
West North
Ridgeline Winds (mph)
Friday
Evening
S
15-25
Friday
Night
SSW
25-35
Saturday
Morning
SSW
40-55
Saturday
Afternoon
WSW
15-25
West Central
Ridgeline Winds (mph)
Friday
Evening
SW
10-20
Friday
Night
SW
20-30
Saturday
Morning
SW
40-55
Saturday
Afternoon
WSW
25-35
West South
Ridgeline Winds (mph)
Friday
Evening
SW
10-20
Friday
Night
SSW
20-30
Saturday
Morning
SW
25-35
Saturday
Afternoon
SW
40-55
Stevens Pass
Ridgeline Winds (mph)
Friday
Evening
SW
5-15
Friday
Night
SSE
5-15
Saturday
Morning
SW
25-35
Saturday
Afternoon
SW
30-40
Snoqualmie Pass
Ridgeline Winds (mph)
Friday
Evening
SW
5-15
Friday
Night
SSE
5-15
Saturday
Morning
SW
25-35
Saturday
Afternoon
SW
35-50
East North
Ridgeline Winds (mph)
Friday
Evening
SW
10-20
Friday
Night
SW
10-20
Saturday
Morning
SW
25-35
Saturday
Afternoon
WSW
20-30
East Central
Ridgeline Winds (mph)
Friday
Evening
SW
5-15
Friday
Night
SSW
15-25
Saturday
Morning
SW
20-30
Saturday
Afternoon
SW
40-55
East South
Ridgeline Winds (mph)
Friday
Evening
SSW
5-15
Friday
Night
SW
10-20
Saturday
Morning
WSW
25-35
Saturday
Afternoon
WSW
40-55
Mt. Hood
Ridgeline Winds (mph)
Friday
Evening
SW
10-20
Friday
Night
WSW
20-30
Saturday
Morning
WSW
25-35
Saturday
Afternoon
WSW
40-55
Issued: 2:13 PM PST Friday, December 17, 2021
Extended Weather Synopsis
We'll be in split-flow Sunday night through the extended with a cut-off low off th California coast and NW flow carving out a trough over western Canada, leaving the PNW in a bit of no man's land. Eventually, moisture will rotate up from the south but the timing and intensity are tough to pin down in this pattern. We can say with higher confidence that gradients and winds will remain offshore (east or southeasterly) with cooler temps on the east side of the Cascades and some milder air along the west slopes of the Cascades and Olympics.
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).