A potent low passed E to W across the central Washington Cascades on Wednesday night, bringing 6-12" to snow to many mountain locations and even 6" of snow to Leavenworth. Following the low, wrap-around moisture coming is streaming into the region with moderate W winds in many locations. Moderate to heavy rain and snow will focus on the west slopes of the Cascades, shifting south from Mt. Baker by mid-morning. Convergence intensification of rain/snow developed over Snohomish and Skagit counties and is likely to shift south during the day. Expect another 4-12" for many locations above 3500 ft. Rain/snow becomes showery Thursday evening and winds continue to decrease into the light to moderate range.
Precipitation becomes slightly more continuous early Friday as a warm front lifts over Washington State before temporary drying from south to north. As SW flow increases aloft throughout the day, low-level flow shifts easterly during the morning hours, keeping the passes slightly cooler as heavier frontal precipitation works into the Cascades during the afternoon. Warming temperatures aloft may overcome the slightly cooler air at pass level, likely bringing a changeover to rain at Snoqualmie Pass level.
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 rain and snow showers. Light to moderate winds.
Thursday
Night
Increasing very light rain and snow after midnight. Light winds.
Thursday
Decreasing moderate snow early, then light rain and snow showers. Light winds.
Thursday
Night
Light snow showers becoming increasing light snow after midnight. Light to moderate winds.
Thursday
Decreasing moderate to heavy snow in the morning with convergence intensification, then light rain and snow showers in the afternoon. Decreasing moderate winds.
Thursday
Night
Decreasing light snow showers in the evening, then increasing light snow after midnight. Light to moderate winds.
Thursday
Moderate rain and snow (Paradise and White Pass), light rain/snow at Crystal; becoming showery late in the day. Decreasing moderate winds.
Thursday
Night
Decreasing light snow showers in the evening, then increasing light snow after midnight. Light to moderate winds.
Thursday
Moderate rain and snow, heavy at times in convergence bands. Decreasing light to moderate winds at ridgeline and W at pass level.
Thursday
Night
Decreasing light snow showers in the evening, then increasing light snow after midnight. Light ridgeline winds and light W winds at pass level.
Thursday
Moderate rain and snow, heavy at times. Decreasing moderate winds at ridgeline and W at pass level.
Thursday
Night
Decreasing light snow showers in the evening, then increasing light snow after midnight. Moderate ridgeline winds and light W winds at pass level.
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).