Issued: 2:15 PM PDT Thursday, March 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 deep, but weakening cold upper low-pressure center offshore continues to feed bands of moisture into the region on SSW flow. A N-S frontal rainband of moderate to occasionally heavy precipitation extends from the coast eastward to I-5 early Thursday afternoon. This band should progress eastward and bring moderate rain and snow to the Cascades Thursday evening before exiting and leaving very light shower activity overnight. The front should displace the mild air over the region on Thursday with snow levels dropping below all major pass levels by Friday morning.

Additional bands of rain and snow arrive as the weakening upper low moves into the near-shore waters on Friday. Snow levels should fluctuate around 2500-3500 ft with convective showers becoming increasingly common during the afternoon hours. Heavier bands of showers proximal to the closed low should take aim at the Olympics and Cascades West North zones while lighter snow showers predominate elsewhere. Expect slightly more convective activity Friday afternoon with graupel and locally high snowfall rates. Snow may become heavy and wet or could mix with rain as temperatures bump above freezing at Snoqualmie Pass level in the afternoon.

The weakened upper low makes its way toward the mouth of the Columbia River and becomes a trough Friday night with light to moderate snow shower activity continuing across the region. Flow switches NW as the trough exits to the east on Saturday with gradually decreasing light to occasionally moderate snow showers and weak potential convergence. Temperatures remain near or below seasonal norms with light snow accumulations at all the major passes.

 

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
Thursday Night Light rain and snow showers, increasing and becoming steadier after midnight. Cooler.
Friday Moderate to heavy rain and snow.
Thursday Night Moderate rain and snow during the evening, then becoming light and showery. Cooler.
Friday Increasing moderate rain and snow, heavy at times in the afternoon.
Thursday Night Moderate rain and snow during the evening, then becoming light and showery. Cooler.
Friday Increasing light rain and snow showers.
Thursday Night Light to occasionally moderate rain and snow during the evening, then becoming light and showery. Cooler.
Friday Increasing light rain and snow showers.
Thursday Night Moderate rain and snow during the evening, then becoming light and showery. Cooler. Variable winds switch light E at the Pass after midnight.
Friday Increasing light rain and snow showers. Light E winds become variable at the pass by the afternoon.
Thursday Night Moderate rain and snow during the evening, then becoming light and showery. Cooler. Variable winds switch light E at the Pass after midnight.
Friday Increasing light rain and snow showers. Light E winds become variable at the pass by the afternoon.
Thursday Night Light to moderate rain and snow during the early evening tapering to snow flurries from the late evening onwards. Cooler.
Friday Increasing light rain and snow showers.
Thursday Night Light to moderate rain and snow during the early evening tapering to snow flurries from the late evening onwards. Cooler.
Friday Very light rain and snow showers possible.
Thursday Night Light rain and snow during the evening, tapering to snow flurries after midnight.
Friday Increasing light rain and snow showers.
Thursday Night Light to moderate rain and snow during the evening hours tapering to snow flurries. Cooler.
Friday Increasing light rain and snow showers.

Issued: 2:15 PM PDT Thursday, March 18, 2021

Precipitation (in)

Thursday Night Friday Friday Night Saturday
5 pm - 5 am 5 am - 5 pm 5 pm - 5 am 5 am - 5 pm
Hurricane Ridge 0.25 0.75 0.25 LT 0.10
Mt Baker Ski Area 0.25 - 0.50 0.75 0.50 LT 0.10
Mt. Loop - Barlow Pass 0.50 0.25 0.50 0.25
Stevens Pass 0.25 - 0.50 LT 0.10 LT 0.25 LT 0.25
Snoqualmie Pass 0.25 - 0.50 LT 0.10 LT 0.25 0.25
Crystal Mt 0.25 0.25 0.25 LT 0.10
Paradise 0.25 0.25 0.25 - 0.50 0.25 - 0.50
White Pass 0.25 LT 0.10 LT 0.25 LT 0.25
Washington Pass 0.25 - 0.50 LT 0.25 LT 0.25 LT 0.10
Mission Ridge 0.25 LT 0.10 LT 0.10 LT 0.10
Salmon la Sac - Gallagher Head 0.25 - 0.50 LT 0.10 LT 0.25 LT 0.10
Tieton River - Darland Mt. 0.25 LT 0.25 LT 0.25 LT 0.10
Mt Hood Meadows 0.25 LT 0.25 0.25 0.50
Timberline 0.25 LT 0.25 0.25 0.50
Hurricane Ridge Precipitation (in)
Thursday Night 0.25
Friday 0.75
Friday Night 0.25
Saturday LT 0.10
Mt Baker Ski Area Precipitation (in)
Thursday Night 0.25 - 0.50
Friday 0.75
Friday Night 0.50
Saturday LT 0.10
Mt. Loop - Barlow Pass Precipitation (in)
Thursday Night 0.50
Friday 0.25
Friday Night 0.50
Saturday 0.25
Stevens Pass Precipitation (in)
Thursday Night 0.25 - 0.50
Friday LT 0.10
Friday Night LT 0.25
Saturday LT 0.25
Snoqualmie Pass Precipitation (in)
Thursday Night 0.25 - 0.50
Friday LT 0.10
Friday Night LT 0.25
Saturday 0.25
Crystal Mt Precipitation (in)
Thursday Night 0.25
Friday 0.25
Friday Night 0.25
Saturday LT 0.10
Paradise Precipitation (in)
Thursday Night 0.25
Friday 0.25
Friday Night 0.25 - 0.50
Saturday 0.25 - 0.50
White Pass Precipitation (in)
Thursday Night 0.25
Friday LT 0.10
Friday Night LT 0.25
Saturday LT 0.25
Washington Pass Precipitation (in)
Thursday Night 0.25 - 0.50
Friday LT 0.25
Friday Night LT 0.25
Saturday LT 0.10
Mission Ridge Precipitation (in)
Thursday Night 0.25
Friday LT 0.10
Friday Night LT 0.10
Saturday LT 0.10
Salmon la Sac - Gallagher Head Precipitation (in)
Thursday Night 0.25 - 0.50
Friday LT 0.10
Friday Night LT 0.25
Saturday LT 0.10
Tieton River - Darland Mt. Precipitation (in)
Thursday Night 0.25
Friday LT 0.25
Friday Night LT 0.25
Saturday LT 0.10
Mt Hood Meadows Precipitation (in)
Thursday Night 0.25
Friday LT 0.25
Friday Night 0.25
Saturday 0.50
Timberline Precipitation (in)
Thursday Night 0.25
Friday LT 0.25
Friday Night 0.25
Saturday 0.50

Issued: 2:15 PM PDT Thursday, March 18, 2021

Snow Level (ft)

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

Issued: 2:15 PM PDT Thursday, March 18, 2021

5000' Temperatures (°F)

Thursday Night Friday
Max / Min Max / Min
Olympics 27 / 23 28 / 24
West North 32 / 22 28 / 22
West Central 27 / 20 29 / 21
West South 29 / 24 29 / 25
Stevens Pass 34 / 20 32 / 21
Snoqualmie Pass 27 / 19 30 / 22
East North 34 / 20 32 / 21
East Central 34 / 20 31 / 20
East South 30 / 20 32 / 23
Mt. Hood 31 / 23 32 / 25
Olympics 5000' Temperature Forecast
(Max / Min)
Thursday Night 27 / 23
Friday 28 / 24
West North 5000' Temperature Forecast
(Max / Min)
Thursday Night 32 / 22
Friday 28 / 22
West Central 5000' Temperature Forecast
(Max / Min)
Thursday Night 27 / 20
Friday 29 / 21
West South 5000' Temperature Forecast
(Max / Min)
Thursday Night 29 / 24
Friday 29 / 25
Stevens Pass 5000' Temperature Forecast
(Max / Min)
Thursday Night 34 / 20
Friday 32 / 21
Snoqualmie Pass 5000' Temperature Forecast
(Max / Min)
Thursday Night 27 / 19
Friday 30 / 22
East North 5000' Temperature Forecast
(Max / Min)
Thursday Night 34 / 20
Friday 32 / 21
East Central 5000' Temperature Forecast
(Max / Min)
Thursday Night 34 / 20
Friday 31 / 20
East South 5000' Temperature Forecast
(Max / Min)
Thursday Night 30 / 20
Friday 32 / 23
Mt. Hood 5000' Temperature Forecast
(Max / Min)
Thursday Night 31 / 23
Friday 32 / 25

Issued: 2:15 PM PDT Thursday, March 18, 2021

Ridgeline Winds (mph)

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

Issued: 2:15 PM PDT Thursday, March 18, 2021

Extended Weather Synopsis

Cool WNW flow maintains light snow showers along the west slopes of the Cascades Saturday night. A deep low aimed for the southern tip of the Alaskan panhandle extends a leading warm front followed quickly by a cold front, both dropping SE toward our region. The warm front should bring increased rain and snow later Sunday afternoon. Any warm-up will be short-lived Sunday evening with additional rain and snow associated with the cold frontal passage. Snow levels drop behind the cold front and precipitation becomes showery with the trough axis over the region early Monday morning. Showers and convergence activity continue, becoming lighter throughout the day on Monday as flow turns increasingly northerly. Snow levels remain relatively steady below 3000 ft throughout the extended forecast period.

Extended Snow Level (ft)

Saturday Night Sunday Sunday Night Monday
West North 2000' 1500' 2000' 2000'
Snoqualmie Pass 2000' 2000' 2000' 2000'
Mt. Hood 2500' 2000' 2500' 2500'
West North Elevation
Saturday Night 2000'
Sunday 1500'
Sunday Night 2000'
Monday 2000'
Snoqualmie Pass Elevation
Saturday Night 2000'
Sunday 2000'
Sunday Night 2000'
Monday 2000'
Mt. Hood Elevation
Saturday Night 2500'
Sunday 2000'
Sunday Night 2500'
Monday 2500'

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

Previous forecast from Mar 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’.