Issued: 2:06 PM PST Monday, November 16, 2020
by Robert Hahn

Jump to: Weather Forecast I Snow/Freezing Level I Precipitation I Free Winds 5k I Free Winds 9k I Extended Weather

Weather Synopsis for Monday night through Wednesday

A rapidly intensifying storm tracks NNE toward the norther tip of Vancouver Island Monday through Tuesday morning and will become the deepest low pressure system to impact our region so far this season. The powerful storm has tapped into subtropical moisture and temperatures which continue to invade the NWAC forecast region on strong SSW flow from late Monday through Tuesday morning. The first act, a northward-lifting warm front continues to bring moderate to locally heavy precipitation to our mountains along with rapidly rising snow levels through Monday evening. By this time, most of the moisture should focus on the North Cascades and Mt. Baker regions where up to an inch of additional water could fall before the frontal moisture fully exits into Canada. Thereafter, relatively dry, cloudy, and very mild conditions characterize the warm sector of this storm through early Tuesday morning. E low-level flow should initially keep parts of the NE Cascades cooler, but the sustained SSW winds aloft will gradually scour out the lingering cool air by Tuesday morning.  The second act of the storm, the associated cold-frontal feature spreads moderate to heavy rain, very high elevation snow (above 7000-9000 ft), and further strengthening SSW winds out ahead of it from the already strong winds Monday night. They will be particularly strong in exposed areas in the Mt. Baker and Olympics regions where extreme winds are likely in the alpine. The front should cross the Cascades shortly after noon. 

Moderate rain and snow showers continue behind the front on a brisk, but decreasing SW flow Tuesday afternoon, decreasing slightly overnight as cooler air moves back, lowering snow levels lower to near pass levels by Wednesday morning. A more organized feature should bring another shot of more sustained moderate rain and snow during the late morning and mid-day hours on Wednesday before more showery weather returns by afternoon.

From Tuesday afternoon through the end of the day on Wednesday, the most significant snow accumulations will be at mid and upper elevations on the Cascades Volcanoes where 1-2 ft of snow are possible.

Weather Forecast

Hurricane Ridge
Monday Night Lingering light to moderate rain in evening, then becoming cloudy. Very mild with continued warming. Moderate to strong winds in the evening becoming strong.
Mt. Baker
Monday Night Heavy rain and high elevation snow tapering and ending by midnight. Snow possible at the highest elevations. Continued rapidly rising snow levels. Moderate to strong winds in the evening becoming moderate with strong gusts after midnight.
Washington Pass and Leavenworth
Monday Night Moderate rain and snow ending in the evening, then becoming cloudy. Rising snow levels. Moderate to strong 5000 ft winds. E flow likely to keep Washington Pass as snow.
Stevens and Snoqualmie Pass
Monday Night Light rain ending in the early evening, then cloudy. Moderate 5000 ft winds. Moderate E winds through the passes.
Mt. Rainier, Crystal and White Pass
Monday Night Light sprinkles ending in the early evening, then cloudy. Very mild with above freezing temperatures extending well into the alpine. Moderate 5000 ft winds that may be strong to extreme in the alpine.
Mt. Hood
Monday Night Cloudy and very mild. Moderate winds at 5000 ft, with strong winds in the alpine.

Snow/Freezing Level (ft)

Hurricane Ridge Mt. Baker Washington Pass Leavenworth Stevens Pass Snoqualmie Pass Mt. Rainier, Crystal & White Pass Mt. Hood
Monday Evening Snow Level * 8500' 6000' 4000' 6000' 6000' 8000' 9000' 10000'
Monday Night Snow Level * 9500' 8500' 7500' 9500' 9000' 10000' 10500' 10500'
Tuesday Morning Snow Level * 8000' 8500' 7000' 9000' 8500' 9000' 8500' 9000'
Tuesday Afternoon Snow Level * 5500' 5500' 5500' 5500' 5500' 5500' 5500' 6000'
Tuesday Evening Snow Level 4000' 4500' 4500' 5000' 4500' 4500' 4500' 5000'
Tuesday Night Snow Level 3500' 3500' 4000' 4000' 3500' 4000' 4000' 4000'
Wednesday Morning Snow Level * 3500' 3000' 2500' 3000' 2500' 3000' 3000' 4000'
Hurricane Ridge Elevation
Monday Evening Snow Level
8500'
(Easterly Flow *)
Monday Night Snow Level
9500'
(Easterly Flow *)
Tuesday Morning Snow Level
8000'
(Easterly Flow *)
Tuesday Afternoon Snow Level
5500'
(Easterly Flow *)
Tuesday Evening Snow Level
4000'
Tuesday Night Snow Level
3500'
Wednesday Morning Snow Level
3500'
(Easterly Flow *)
Wednesday Afternoon Snow Level
3000'
Mt. Baker Elevation
Monday Evening Snow Level
6000'
(Easterly Flow *)
Monday Night Snow Level
8500'
(Easterly Flow *)
Tuesday Morning Snow Level
8500'
(Easterly Flow *)
Tuesday Afternoon Snow Level
5500'
(Easterly Flow *)
Tuesday Evening Snow Level
4500'
Tuesday Night Snow Level
3500'
Wednesday Morning Snow Level
3000'
(Easterly Flow *)
Wednesday Afternoon Snow Level
3000'
Washington Pass Elevation
Monday Evening Snow Level
4000'
(Easterly Flow *)
Monday Night Snow Level
7500'
(Easterly Flow *)
Tuesday Morning Snow Level
7000'
(Easterly Flow *)
Tuesday Afternoon Snow Level
5500'
(Easterly Flow *)
Tuesday Evening Snow Level
4500'
Tuesday Night Snow Level
4000'
Wednesday Morning Snow Level
2500'
(Easterly Flow *)
Wednesday Afternoon Snow Level
3500'
Leavenworth Elevation
Monday Evening Snow Level
6000'
(Easterly Flow *)
Monday Night Snow Level
9500'
(Easterly Flow *)
Tuesday Morning Snow Level
9000'
(Easterly Flow *)
Tuesday Afternoon Snow Level
5500'
(Easterly Flow *)
Tuesday Evening Snow Level
5000'
Tuesday Night Snow Level
4000'
Wednesday Morning Snow Level
3000'
(Easterly Flow *)
Wednesday Afternoon Snow Level
3000'
Stevens Pass Elevation
Monday Evening Snow Level
6000'
(Easterly Flow *)
Monday Night Snow Level
9000'
(Easterly Flow *)
Tuesday Morning Snow Level
8500'
(Easterly Flow *)
Tuesday Afternoon Snow Level
5500'
(Easterly Flow *)
Tuesday Evening Snow Level
4500'
Tuesday Night Snow Level
3500'
Wednesday Morning Snow Level
2500'
(Easterly Flow *)
Wednesday Afternoon Snow Level
3500'
Snoqualmie Pass Elevation
Monday Evening Snow Level
8000'
(Easterly Flow *)
Monday Night Snow Level
10000'
(Easterly Flow *)
Tuesday Morning Snow Level
9000'
(Easterly Flow *)
Tuesday Afternoon Snow Level
5500'
(Easterly Flow *)
Tuesday Evening Snow Level
4500'
Tuesday Night Snow Level
4000'
Wednesday Morning Snow Level
3000'
(Easterly Flow *)
Wednesday Afternoon Snow Level
3500'
Mt. Rainier & Crystal Elevation
Monday Evening Snow Level
9000'
(Easterly Flow *)
Monday Night Snow Level
10500'
(Easterly Flow *)
Tuesday Morning Snow Level
8500'
(Easterly Flow *)
Tuesday Afternoon Snow Level
5500'
(Easterly Flow *)
Tuesday Evening Snow Level
4500'
Tuesday Night Snow Level
4000'
Wednesday Morning Snow Level
3000'
(Easterly Flow *)
Wednesday Afternoon Snow Level
3500'
Mt. Hood Elevation
Monday Evening Snow Level
10000'
(Easterly Flow *)
Monday Night Snow Level
10500'
(Easterly Flow *)
Tuesday Morning Snow Level
9000'
(Easterly Flow *)
Tuesday Afternoon Snow Level
6000'
(Easterly Flow *)
Tuesday Evening Snow Level
5000'
Tuesday Night Snow Level
4000'
Wednesday Morning Snow Level
4000'
(Easterly Flow *)
Wednesday Afternoon Snow Level
3500'

* Easterly flow in the Cascade Passes can cause locally lower Snow or Freezing levels than areas further west.
Freezing Level is when no precipitation is forecast.

Precipitation Forecast

Monday Night Tuesday Tuesday Night Wednesday
4 pm - 4 am 4 am - 4 pm 4 pm - 4 am 4 am - 4 pm
Hurricane Ridge 0.25 - 0.50 0.50 - 0.75 LT 0.25 0.25
Mt Baker Ski Area 1.00 0.75 0.75 -1.00 0.75
Washington Pass 0.50 0.25 0.25 - 0.50 0.25
Leavenworth LT 0.10 LT 0.10 LT 0.10 LT 0.25
Stevens Pass LT 0.10 LT 0.25 0.25 - 0.50 0.25
Snoqualmie Pass 0 0.25 0.25 - 0.50 0.25 - 0.50
Mission Ridge 0 0 LT 0.10 0.25
Crystal Mt LT 0.10 0.50 0.25 - 0.50 0.50
Paradise LT 0.10 0.75 0.75 1.00
White Pass 0 0.25 0.25 - 0.50 0.50
Mt Hood Meadows 0 0.25 - 0.50 0.25 0.75 -1.00
0 0.25 - 0.50 0.25 0.75
Hurricane Ridge Precipitation Forecast
Monday Night 0.25 - 0.50
Tuesday 0.50 - 0.75
Tuesday Night LT 0.25
Wednesday 0.25
Mt Baker Ski Area Precipitation Forecast
Monday Night 1.00
Tuesday 0.75
Tuesday Night 0.75 -1.00
Wednesday 0.75
Washington Pass Precipitation Forecast
Monday Night 0.50
Tuesday 0.25
Tuesday Night 0.25 - 0.50
Wednesday 0.25
Leavenworth Precipitation Forecast
Monday Night LT 0.10
Tuesday LT 0.10
Tuesday Night LT 0.10
Wednesday LT 0.25
Stevens Pass Precipitation Forecast
Monday Night LT 0.10
Tuesday LT 0.25
Tuesday Night 0.25 - 0.50
Wednesday 0.25
Snoqualmie Pass Precipitation Forecast
Monday Night 0
Tuesday 0.25
Tuesday Night 0.25 - 0.50
Wednesday 0.25 - 0.50
Mission Ridge Precipitation Forecast
Monday Night 0
Tuesday 0
Tuesday Night LT 0.10
Wednesday 0.25
Crystal Mt Precipitation Forecast
Monday Night LT 0.10
Tuesday 0.50
Tuesday Night 0.25 - 0.50
Wednesday 0.50
Paradise Precipitation Forecast
Monday Night LT 0.10
Tuesday 0.75
Tuesday Night 0.75
Wednesday 1.00
White Pass Precipitation Forecast
Monday Night 0
Tuesday 0.25
Tuesday Night 0.25 - 0.50
Wednesday 0.50
Mt Hood Meadows Precipitation Forecast
Monday Night 0
Tuesday 0.25 - 0.50
Tuesday Night 0.25
Wednesday 0.75 -1.00
Timberline Precipitation Forecast
Monday Night 0
Tuesday 0.25 - 0.50
Tuesday Night 0.25
Wednesday 0.75

Free Winds at 5000' (mph)

Hurricane Ridge Mt. Baker Stevens to Snoqualmie Pass Mt. Rainier Mt. Hood
Monday Evening SSW 25 - 35 S 25 - 35 SSE 20 - 30 SSE 20 - 30 S 20 - 30
Monday Night SSE 30 - 40 SSE 20 - 30 ESE 20 - 30 ESE 20 - 30 SE 15 - 25
Tuesday Morning S 40 - 55 S 45 - 65 ESE 30 - 40 SSE 35 - 45 S 30 - 40
Hurricane Ridge Elevation
Monday Evening SSW 25 - 35
Monday Night SSE 30 - 40
Tuesday Morning S 40 - 55
Tuesday Afternoon SSW 30 - 40
Mt. Baker Elevation
Monday Evening S 25 - 35
Monday Night SSE 20 - 30
Tuesday Morning S 45 - 65
Tuesday Afternoon SSE 35 - 50
Stevens and Snoqualmie Pass Elevation
Monday Evening SSE 20 - 30
Monday Night ESE 20 - 30
Tuesday Morning ESE 30 - 40
Tuesday Afternoon S 30 - 40
Mt. Rainier Elevation
Monday Evening SSE 20 - 30
Monday Night ESE 20 - 30
Tuesday Morning SSE 35 - 45
Tuesday Afternoon S 30 - 40
Mt. Hood Elevation
Monday Evening S 20 - 30
Monday Night SE 15 - 25
Tuesday Morning S 30 - 40
Tuesday Afternoon SE 30 - 40
Hurricane Ridge Direction - Speed
Monday Evening SSW 25 - 35
Monday Night SSE 30 - 40
Tuesday Morning S 40 - 55
Tuesday Afternoon SSW 30 - 40
Mt. Baker Direction - Speed
Monday Evening S 25 - 35
Monday Night SSE 20 - 30
Tuesday Morning S 45 - 65
Tuesday Afternoon SSE 35 - 50
Stevens and Snoqualmie Pass Direction - Speed
Monday Evening SSE 20 - 30
Monday Night ESE 20 - 30
Tuesday Morning ESE 30 - 40
Tuesday Afternoon S 30 - 40
Mt. Rainier Direction - Speed
Monday Evening SSE 20 - 30
Monday Night ESE 20 - 30
Tuesday Morning SSE 35 - 45
Tuesday Afternoon S 30 - 40
Mt. Hood Direction - Speed
Monday Evening S 20 - 30
Monday Night SE 15 - 25
Tuesday Morning S 30 - 40
Tuesday Afternoon SE 30 - 40

Directions above indicate the direction the wind blows from on the 16-point cardinal scale. These winds indicate "free" winds, or those winds in the atmosphere not influenced by terrain. Topographical effects may produce greater or lower wind speeds in certain locations as well as significant variations in direction.

Free Winds at 9000' (mph)

Mt. Baker Washington Pass Stevens to Snoqualmie Pass Mt. Rainier Mt. Hood
Monday Evening SW 50 - 70 SW 40 - 60 SW 50 - 70 SW 45 - 65 SW 45 - 65
Monday Night SW 45 - 65 SW 35 - 50 SW 40 - 60 SW 40 - 60 SW 45 - 65
Tuesday Morning S 40 - 60 S 35 - 50 SSW 40 - 60 SSW 50 - 70 SSW 50 - 70
Mt. Baker Direction - Speed
Monday Evening SW 50 - 70
Monday Night SW 45 - 65
Tuesday Morning S 40 - 60
Tuesday Afternoon SSW 50 - 70
Washington Pass Direction - Speed
Monday Evening SW 40 - 60
Monday Night SW 35 - 50
Tuesday Morning S 35 - 50
Tuesday Afternoon SSW 35 - 50
Stevens and Snoqualmie Pass Direction - Speed
Monday Evening SW 50 - 70
Monday Night SW 40 - 60
Tuesday Morning SSW 40 - 60
Tuesday Afternoon SW 50 - 70
Mt. Rainier Direction - Speed
Monday Evening SW 45 - 65
Monday Night SW 40 - 60
Tuesday Morning SSW 50 - 70
Tuesday Afternoon WSW 35 - 50
Mt. Hood Direction - Speed
Monday Evening SW 45 - 65
Monday Night SW 45 - 65
Tuesday Morning SSW 50 - 70
Tuesday Afternoon WSW 45 - 65

Extended Weather Synopsis for Wednesday night through Friday

Cool, unsettled, and showery weather prevails as the upper trough moves onshore and settles in over the region with moderate snow shower activity expected Wednesday evening and becoming light on Thursday, further decreasing going forward in time. The timing of organized features will be difficult to predict this far out. Snow levels drop below pass level. WSW flow Wednesday night and Thursday morning should shift W by Thursday afternoon with the trough directly over the region.

Extended Snow/Freezing Levels

Mt. Baker Snoqualmie Pass Mt. Hood Easterly Flow *
Wednesday Night Snow Level 1500' - 2500' 2000' - 3000' 2000' - 3000'
Thursday Snow Level 1000' - 2000' 1500' - 2500' 2000' - 3000'
Thursday Night Snow Level 1000' - 2000' 1500' - 2500' 1500' - 2500'
Mt. Baker Elevation
Wednesday Night Snow Level
1500' - 2500'
Thursday Snow Level
1000' - 2000'
Thursday Night Snow Level
1000' - 2000'
Friday Snow Level
1500' - 2500'
Snoqualmie Pass Elevation
Wednesday Night Snow Level
2000' - 3000'
Thursday Snow Level
1500' - 2500'
Thursday Night Snow Level
1500' - 2500'
Friday Snow Level
2000' - 3000'
Mt. Hood Elevation
Wednesday Night Snow Level
2000' - 3000'
Thursday Snow Level
2000' - 3000'
Thursday Night Snow Level
1500' - 2500'
Friday Snow Level
2000' - 3000'

* Easterly flow in the Cascade Passes can cause locally lower Snow or Freezing levels than areas further west.
Freezing Level is when no precipitation is forecast.

Jump to: Weather Forecast I Snow/Freezing Level I Precipitation I Free Winds 5k I Free Winds 9k I Extended Weather

Previous forecast from Nov 15, 2020

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.