Issued: 2:02 PM PST Monday, January 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

Northerly flow weakens Monday night as an offshore ridge flattens and the axis shifts over the Pacific Northwest early Tuesday. The northerly flow aloft with a ridge offshore allows cool air to pool east of the Cascade Crest while freezing levels rise west of the Cascade Crest. Low-level winds shift easterly spilling the cool air east of the mountains through the mountain gaps into the mid-day hours Tuesday. Expect a low-level inversion for the first half of the day Tuesday in the passes. Having sent most of its moisture into northern British Columbia, the weakening trail end of a frontal system approaches from the NW later Tuesday bringing light but increasing WSW ridgeline winds out ahead of it. Widespread mid-level clouds with some filtered sunshine can be expected during the day Tuesday. The front arrives Tuesday evening spreading some very light rain and snow at 3000-4000 ft snow levels as it passes south and fizzles by Wednesday morning. Less than a tenth of water equivalent can be expected in all areas. Moderate ridgeline winds and strong gusts can be expected east of the Cascade crest in favored down-slope locations late Tuesday and Tuesday night.

Wednesday should be dry and cool with mostly cloudy skies and decreasing clouds in the afternoon. Winds should also decrease and become variable late in the day.

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
Monday Night Increasing high clouds. Low clouds possible in the valleys.
Tuesday Filtered sunshine with periods of slightly thicker clouds possible.
Monday Night Mostly clear to start with increasing high clouds. Low clouds possible in the valleys.
Tuesday Filtered sunshine with periods of slightly thicker clouds possible.
Monday Night Mostly clear to start with increasing high clouds. Low clouds possible in the valleys.
Tuesday Filtered sunshine with periods of slightly thicker clouds possible.
Monday Night Mostly clear to start with increasing high clouds. Low clouds possible in the valleys.
Tuesday Filtered sunshine with periods of slightly thicker clouds possible.
Monday Night Mostly clear to start with increasing high clouds. Low clouds possible in the valleys.
Tuesday Filtered sunshine with periods of slightly thicker clouds possible.
Monday Night Mostly clear to start with increasing high clouds. Low clouds possible in the valleys.
Tuesday Filtered sunshine with periods of slightly thicker clouds possible.
Monday Night Mostly clear to start with increasing high clouds. Low clouds possible in the valleys.
Tuesday Filtered sunshine with periods of slightly thicker clouds possible.
Monday Night Mostly clear to start with increasing high clouds. Low clouds possible in the valleys.
Tuesday Filtered sunshine with periods of slightly thicker clouds possible.
Monday Night Mostly clear to start with increasing high clouds. Low clouds possible in the valleys.
Tuesday Filtered sunshine with periods of slightly thicker clouds possible.
Monday Night Mostly clear to start with increasing high clouds. Low clouds possible in the valleys.
Tuesday Filtered sunshine with periods of slightly thicker clouds possible.

Issued: 2:02 PM PST Monday, January 18, 2021

Precipitation (in)

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 0 LT 0.10 0
Mt Baker Ski Area 0 0 LT 0.10 0
Mt. Loop - Barlow Pass 0 0 LT 0.10 0
Stevens Pass 0 0 LT 0.10 0
Snoqualmie Pass 0 0 LT 0.10 0
Crystal Mt 0 0 0 0
Paradise 0 0 0 0
White Pass 0 0 0 0
Washington Pass 0 0 LT 0.10 0
Mission Ridge 0 0 0 0
Salmon la Sac - Gallagher Head 0 0 0 0
Tieton River - Darland Mt. 0 0 0 0
Mt Hood Meadows 0 0 0 0
Timberline 0 0 0 0
Hurricane Ridge Precipitation (in)
Monday Night 0
Tuesday 0
Tuesday Night LT 0.10
Wednesday 0
Mt Baker Ski Area Precipitation (in)
Monday Night 0
Tuesday 0
Tuesday Night LT 0.10
Wednesday 0
Mt. Loop - Barlow Pass Precipitation (in)
Monday Night 0
Tuesday 0
Tuesday Night LT 0.10
Wednesday 0
Stevens Pass Precipitation (in)
Monday Night 0
Tuesday 0
Tuesday Night LT 0.10
Wednesday 0
Snoqualmie Pass Precipitation (in)
Monday Night 0
Tuesday 0
Tuesday Night LT 0.10
Wednesday 0
Crystal Mt Precipitation (in)
Monday Night 0
Tuesday 0
Tuesday Night 0
Wednesday 0
Paradise Precipitation (in)
Monday Night 0
Tuesday 0
Tuesday Night 0
Wednesday 0
White Pass Precipitation (in)
Monday Night 0
Tuesday 0
Tuesday Night 0
Wednesday 0
Washington Pass Precipitation (in)
Monday Night 0
Tuesday 0
Tuesday Night LT 0.10
Wednesday 0
Mission Ridge Precipitation (in)
Monday Night 0
Tuesday 0
Tuesday Night 0
Wednesday 0
Salmon la Sac - Gallagher Head Precipitation (in)
Monday Night 0
Tuesday 0
Tuesday Night 0
Wednesday 0
Tieton River - Darland Mt. Precipitation (in)
Monday Night 0
Tuesday 0
Tuesday Night 0
Wednesday 0
Mt Hood Meadows Precipitation (in)
Monday Night 0
Tuesday 0
Tuesday Night 0
Wednesday 0
Timberline Precipitation (in)
Monday Night 0
Tuesday 0
Tuesday Night 0
Wednesday 0

Issued: 2:02 PM PST Monday, January 18, 2021

Snow Level (ft)

Monday Evening Monday Night* Tuesday Morning* Tuesday Afternoon Tuesday Evening Tuesday Night Wednesday Morning Wednesday Afternoon
Olympics 7000' 7500' 7500' 7500' 5500' 4500' 3000' 3000'
West North 4000' 3500' 4000' 5000' 3000' 2500' 2000' 2500'
West Central 4000' 3000' 3500' 5500' 3500' 3000' 2000' 3000'
West South 4500' 3500' 3500' 7000' 4500' 3500' 3000' 3500'
Stevens Pass 3500' 2500' 2500' 5000' 3000' 2000' 3500' 3000'
Snoqualmie Pass 4500' 3000' 3000' 5500' 4000' 3500' 3000' 3000'
East North 3500' 2500' 2000' 4000' 2500' 2000' 2000' 2500'
East Central 4000' 2500' 2500' 4500' 3500' 2500' 2500' 3500'
East South 4000' 3000' 2500' 5000' 4500' 3500' 3500' 4000'
Mt. Hood 5500' 4000' 3500' 7000' 9000' 8000' 7000' 6000'
Olympics Elevation
Monday Evening 7000'
Monday Night* 7500'
Tuesday Morning* 7500'
Tuesday Afternoon 7500'
Tuesday Evening 5500'
Tuesday Night 4500'
Wednesday Morning 3000'
Wednesday Afternoon 3000'
West North Elevation
Monday Evening 4000'
Monday Night* 3500'
Tuesday Morning* 4000'
Tuesday Afternoon 5000'
Tuesday Evening 3000'
Tuesday Night 2500'
Wednesday Morning 2000'
Wednesday Afternoon 2500'
West Central Elevation
Monday Evening 4000'
Monday Night* 3000'
Tuesday Morning* 3500'
Tuesday Afternoon 5500'
Tuesday Evening 3500'
Tuesday Night 3000'
Wednesday Morning 2000'
Wednesday Afternoon 3000'
West South Elevation
Monday Evening 4500'
Monday Night* 3500'
Tuesday Morning* 3500'
Tuesday Afternoon 7000'
Tuesday Evening 4500'
Tuesday Night 3500'
Wednesday Morning 3000'
Wednesday Afternoon 3500'
Stevens Pass Elevation
Monday Evening 3500'
Monday Night* 2500'
Tuesday Morning* 2500'
Tuesday Afternoon 5000'
Tuesday Evening 3000'
Tuesday Night 2000'
Wednesday Morning 3500'
Wednesday Afternoon 3000'
Snoqualmie Pass Elevation
Monday Evening 4500'
Monday Night* 3000'
Tuesday Morning* 3000'
Tuesday Afternoon 5500'
Tuesday Evening 4000'
Tuesday Night 3500'
Wednesday Morning 3000'
Wednesday Afternoon 3000'
East North Elevation
Monday Evening 3500'
Monday Night* 2500'
Tuesday Morning* 2000'
Tuesday Afternoon 4000'
Tuesday Evening 2500'
Tuesday Night 2000'
Wednesday Morning 2000'
Wednesday Afternoon 2500'
East Central Elevation
Monday Evening 4000'
Monday Night* 2500'
Tuesday Morning* 2500'
Tuesday Afternoon 4500'
Tuesday Evening 3500'
Tuesday Night 2500'
Wednesday Morning 2500'
Wednesday Afternoon 3500'
East South Elevation
Monday Evening 4000'
Monday Night* 3000'
Tuesday Morning* 2500'
Tuesday Afternoon 5000'
Tuesday Evening 4500'
Tuesday Night 3500'
Wednesday Morning 3500'
Wednesday Afternoon 4000'
Mt. Hood Elevation
Monday Evening 5500'
Monday Night* 4000'
Tuesday Morning* 3500'
Tuesday Afternoon 7000'
Tuesday Evening 9000'
Tuesday Night 8000'
Wednesday Morning 7000'
Wednesday Afternoon 6000'

Issued: 2:02 PM PST Monday, January 18, 2021

5000' Temperatures (°F)

Monday Night Tuesday
Max / Min Max / Min
Olympics 33 / 28 38 / 31
West North 28 / 26 32 / 27
West Central 29 / 25 34 / 27
West South 30 / 25 39 / 27
Stevens Pass 26 / 22 36 / 23
Snoqualmie Pass 26 / 23 34 / 24
East North 24 / 22 36 / 23
East Central 26 / 22 35 / 22
East South 27 / 21 36 / 21
Mt. Hood 27 / 24 37 / 23
Olympics 5000' Temperature Forecast
(Max / Min)
Monday Night 33 / 28
Tuesday 38 / 31
West North 5000' Temperature Forecast
(Max / Min)
Monday Night 28 / 26
Tuesday 32 / 27
West Central 5000' Temperature Forecast
(Max / Min)
Monday Night 29 / 25
Tuesday 34 / 27
West South 5000' Temperature Forecast
(Max / Min)
Monday Night 30 / 25
Tuesday 39 / 27
Stevens Pass 5000' Temperature Forecast
(Max / Min)
Monday Night 26 / 22
Tuesday 36 / 23
Snoqualmie Pass 5000' Temperature Forecast
(Max / Min)
Monday Night 26 / 23
Tuesday 34 / 24
East North 5000' Temperature Forecast
(Max / Min)
Monday Night 24 / 22
Tuesday 36 / 23
East Central 5000' Temperature Forecast
(Max / Min)
Monday Night 26 / 22
Tuesday 35 / 22
East South 5000' Temperature Forecast
(Max / Min)
Monday Night 27 / 21
Tuesday 36 / 21
Mt. Hood 5000' Temperature Forecast
(Max / Min)
Monday Night 27 / 24
Tuesday 37 / 23

Issued: 2:02 PM PST Monday, January 18, 2021

Ridgeline Winds (mph)

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

Issued: 2:02 PM PST Monday, January 18, 2021

Extended Weather Synopsis

A split flow pattern is expected to develop Wednesday night into early Thursday, bringing our region generally quiet weather with light winds. We expect some light snow showers developing from mid-day Thursday through Thursday evening, associated with a cutoff upper low dropping south. It may end up on a track too far offshore to bring more than some clouds and shifting winds. Behind this feature, low-level E flow should develop as cooler Canadian air works into the region east of the Cascade Crest. Friday appears mostly dry with NNE flow aloft.

Extended Snow Level (ft)

Wednesday Night* Thursday * Thursday Night* Friday *
West North 2500' 1500' 1500' 1000'
Snoqualmie Pass 3000' 1500' 1500' 2000'
Mt. Hood 5500' 4500' 2500' 2500'
West North Elevation
Wednesday Night* 2500'
Thursday * 1500'
Thursday Night* 1500'
Friday * 1000'
Snoqualmie Pass Elevation
Wednesday Night* 3000'
Thursday * 1500'
Thursday Night* 1500'
Friday * 2000'
Mt. Hood Elevation
Wednesday Night* 5500'
Thursday * 4500'
Thursday Night* 2500'
Friday * 2500'

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

Previous forecast from Jan 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’.