Two distinct weather features will merge over the next 12-24 hours over our area. Moisture from the older trough off the California coast will merge with an approaching Pacific frontal system dropping SE along the British Columbia coastline. This will produce bands of light to moderate precipitation streaming over the area today in SW flow aloft. Milder air will keep elevated snow levels west of the Cascade crest for today and much of tonight. For Stevens/Snoqualmie and White Passes, precipitation type/snow level will swap around depending on the wind direction/Pass flow. A switch to cooler easterly flow by late morning should help drag snow levels to Pass level through tonight.
Significant timing differences exist in the cold front's passage either late tonight or Thursday morning, but eventually the surface flow will become westerly with a cooling trend and post-frontal showers during the day on Thursday. The Mt Baker area will likely pick up the most snowfall over the next 36 hours in this pattern.
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 periods of rain and snow.
Wednesday
Night
Periods of light to moderate rain and snow. Strong ridgeline winds.
Wednesday
Moderate to occasionally heavy rain and snow. Strong ridgeline winds.
Wednesday
Night
Periods of light to moderate rain and snow. Winds increasing late.
Wednesday
Periods of light to moderate rain and snow. Strong ridgeline winds.
Wednesday
Night
Periods of light to occasionally moderate rain and snow.
Wednesday
Periods of light to moderate rain and snow, heaviest Paradise area. Strong ridgeline winds trending down in the afternoon.
Wednesday
Night
Periods of light to occasionally moderate rain and snow.
Wednesday
Periods of light to occasionally moderate rain and snow. Light west winds at Pass level becoming easterly in the afternoon.
Wednesday
Night
Periods of light rain and snow. Light east winds at Pass level.
Wednesday
Periods of light to moderate rain and snow. Light west winds at Pass level becoming easterly in the afternoon. Strong westerly ridgeline winds easing in the afternoon.
Wednesday
Night
Periods of light rain and snow. Light east winds at Pass level.
Wednesday
Periods of light to occasionally moderate snow. Strong ridgeline winds easing in the afternoon.
Wednesday
Night
Periods of light rain and snow.
Wednesday
Periods of light rain and snow, occasionally moderate near the Cascade crest.
Wednesday
Night
Periods of light rain and snow.
Wednesday
Periods of light rain and snow, occasionally moderate near the Cascade crest.
Wednesday
Night
Periods of light rain and snow.
Wednesday
Periods of light to occasionally moderate rain and snow. Strong ridgeline winds.
Wednesday
Night
Periods of light to occasionally moderate rain and snow. Strong 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).