A frontal system slides down the back of an offshore high pressure on Wednesday. Rain and snow ahead of the front continues to increase across our region as a SW-NE-oriented front drops southeast. The front should progress rapidly, reaching Snoqualmie Pass around noon and Mt. Hood by mid-afternoon. WSW shift direction only slightly to W behind the front with mountain-enhanced precipitation continuing, although decreasing. High-resolution weather models all indicate the development of a well-defined Puget Sound Convergence Zone (PSCZ). The PSCZ develops around noon near the King-Snohomish county line and drops southward toward Snoqualmie Pass in the late afternoon/early evening hours before dissipating south of I-90 in the late evening. Snow levels close to Snoqualmie Pass level will limit snow accumulations, but we expect 5-10" of snow above 3500 ft for Mt. Baker, Stevens, Snoqualmie, and Mt. Hood.
Rain and snow shower activity gradually decreases Wednesday night with slight cooling as a trough digs southward over the Columbia Basin. Areas from the Mountain Loop south to Mt. Hood could pick up an additional 1-4" of snow Wednesday night.
Mostly cloudy skies and very light snow showers linger west of the Cascade Crest on Thursday with a few sun breaks. Skies should be mostly sunny east of the Cascade Crest.
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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Wednesday
Light to moderate rain and snow transitioning to light showers by late morning.
Wednesday
Night
Decreasing very light rain and snow showers.
Wednesday
Moderate to heavy rain and snow decreasing in the afternoon.
Wednesday
Night
Decreasing very rain and light snow showers.
Wednesday
Moderate to heavy rain and snow with locally intense convergence possible in the afternoon.
Wednesday
Night
Decreasing light rain and snow showers.
Wednesday
Moderate to heavy rain and snow developing at Paradise and White Pass; light at Crystal.
Wednesday
Night
Decreasing light rain and snow showers.
Wednesday
Moderate to heavy rain and snow developing. Convergence possible in the afternoon. Increasing light W wind at the Pass.
Wednesday
Night
Decreasing light rain and snow showers. Light W wind at the Pass.
Wednesday
Moderate to heavy rain and snow developing. Convergence possible in the late afternoon. Increasing light to moderate W wind at the Pass.
Wednesday
Night
Decreasing light rain and snow showers. Light W wind at the Pass.
Wednesday
Light snow, heaviest during the morning hours, then becoming showery late in the day.
Wednesday
Night
Decreasing very light rain and snow showers near the Cascade Crest.
Wednesday
Moderate to occasionally heavy rain and snow western part; light to moderate eastern part. Moderate to strong ridgeline wind gusts.
Wednesday
Night
Decreasing very light rain and snow showers near the Cascade Crest.
Wednesday
Light to moderate rain and snow developing.
Wednesday
Night
Decreasing very light rain and snow showers near the Cascade Crest.
Wednesday
Increasing rain and snow, becoming moderate by mid-morning. Strong ridgeline winds.
Wednesday
Night
Decreasing light to moderate rain and snow becoming showers late in the day.
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).