A well-organized front moves through the area from the WNW on Thursday morning. Moderate to strong WSW winds and a cohesive band of precipitation push ahead of the front. Westerly winds pick up behind the front, continuing moderate snow shower activity focused on the west slopes of the Cascades with some spillover onto the east slopes of the Cascades. A convergence forms Thursday within the post-frontal showers and vacillates between the Mtn Loop and Snoqualmie Pass, but focuses more on Stevens Pass. Expect periods of strong winds for the major mountain gaps and sustained strong winds for the east slopes of the Cascades and Mt. Hood with the strongest winds in the early afternoon hours. Snow levels peak in the 1000-2500 ft range during the mid-day hours.
Moderate snow showers and convergence continue in the same general areas for the evening hours with the shower activity becoming light to moderate overnight as snow levels lower to just above sea level.
On Friday, a trough digs offshore with continued light to moderate snow showers focused on the west slopes of the Cascades with light spillover. Winds gradually switch to the SW as the day progresses, potentially increasing snowfall rates late in the day for Mt. Baker.
Weather Forecast
Olympics
West North
West Central
West South
Stevens Pass
Snoqualmie Pass
East North
East Central
East South
Mt. Hood
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Thursday
Decreasing light to moderate snow showers. Moderate ridgeline winds.
Thursday
Night
Light snow showers. Moderate ridgeline winds.
Thursday
Moderate to heavy snow becoming light to moderate snow showers by mid-morning. Strong ridgeline winds becoming moderate.
Thursday
Night
Light to moderate snow showers. Moderate ridgeline winds.
Thursday
Heavy snow in the morning. Moderate snow showers, heavy in convergence (southern part). Moderate ridgeline winds.
Thursday
Night
Moderate snow showers, locally heavy in convergence (southern part). Moderate ridgeline winds.
Thursday
Heavy snow at Paradise in the morning becoming light to moderate showers. Light to moderate snow becoming showering at Crystal and White Pass. Increasing moderate ridgeline winds may become strong.
Thursday
Night
Light to moderate snow showers, heaviest at Paradise. Moderate to strong ridgeline winds decreasing.
Thursday
Moderate to heavy snow and convergence possible over the region in the afternoon. Moderate ridgeline and increasing light to moderate W wind at the Pass.
Thursday
Night
Decreasing moderate snow showers, heaviest in convergence during the evening hours. Moderate ridgeline and light W wind at the pass.
Thursday
Moderate to heavy snow. Convergence possible late in the day. Moderate ridgeline and increasing light to moderate W wind at the Pass.
Thursday
Night
Decreasing moderate snow showers. Moderate ridgeline and decreasing light to moderate W wind at the pass.
Thursday
Moderate snow decreasing in the afternoon. Increasing strong ridgeline winds.
Thursday
Night
Light to moderate snow showers. Moderate ridgeline winds.
Thursday
Moderate snow transitioning to showers. Increasing strong ridgeline winds.
Thursday
Night
Light to moderate snow showers.
Thursday
Light snow changing to showers. Moderate ridgeline winds with strong gusts.
Thursday
Night
Light snow showers. Moderate ridgeline winds with strong gusts.
Thursday
Moderate to occasionally heavy snow. Strong to extreme ridgeline winds.
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).