We're in for a cool snow-showery few days as an unseasonably cold upper level trough takes up residence over the PNW. Snow showers will pile up a few inches today and Friday evening, with the heaviest amounts along the west slopes of the Cascades and Mt Hood. A Puget Sound Convergence zone will likely form this afternoon and last through Friday evening, favoring the Hwy 2 and more likely the I-90 corridor with some heavier hourly snowfall rates. Westerly ridgeline winds will continue to blow through this evening as well. Showers should become more scattered late Friday night.
On Saturday, we'll see showers increase in the afternoon once again with a cool unstable air mass overhead and daytime heating. With increasing instability in the afternoon expect some showers to contain graupel each day. Temperatures will be unseasonably cold for the end of March.
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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Friday
Mostly cloudy with light to occasionally moderate snow showers. Moderate ridgeline winds.
Friday
Night
Mostly cloudy with scattered light snow showers. Moderate ridgeline winds.
Friday
Mostly cloudy with light to occasionally moderate snow showers.
Friday
Night
Mostly cloudy with light to occasionally moderate snow showers.
Friday
Mostly cloudy with light to occasionally moderate snow showers. Showers becoming heavier in the afternoon.
Friday
Night
Mostly cloudy with light to occasionally moderate snow showers. Showers heaviest near areas of convergence in the evening. Moderate ridgeline winds.
Friday
Mostly cloudy with light to occasionally moderate snow showers. Moderate ridgeline winds.
Friday
Night
Mostly cloudy with light to occasionally moderate snow showers. Moderate to strong ridgeline winds.
Friday
Mostly cloudy with light to occasionally moderate snow showers. Light to moderate W Pass level and ridgeline winds.
Friday
Night
Mostly cloudy with light to occasionally moderate snow showers. Showers heaviest near areas of convergence in the evening. Moderate W Pass level and ridgeline winds.
Friday
Mostly cloudy with light to occasionally moderate snow showers. Showers becoming heavier in the afternoon. Moderate W Pass level and ridgeline winds.
Friday
Night
Mostly cloudy with light to moderate snow showers. Showers heaviest near areas of convergence in the evening. Moderate to strong W Pass level and ridgeline winds.
Friday
Mostly cloudy with scattered light snow showers near the Cascade crest, partly sunny further east.
Friday
Night
Mostly cloudy with scattered light snow showers near the Cascade crest, partly cloudy further east.
Friday
Mostly cloudy with light to occasionally moderate snow showers near the Cascade crest, partly sunny further east. Moderate ridgeline winds.
Friday
Night
Mostly cloudy with scattered light snow showers near the Cascade crest, partly cloudy further east. Locally light to moderate snow showers downwind of the convergence zone. Moderate to strong ridgeline winds.
Friday
Mostly cloudy with light to occasionally moderate snow showers near the Cascade crest, partly sunny further east.
Friday
Night
Mostly cloudy with scattered light snow showers near the Cascade crest, partly cloudy further east. Moderate ridgeline winds.
Friday
Cloudy with light to moderate snow showers. Moderate to strong ridgeline winds.
Friday
Night
Mostly cloudy with light to moderate snow showers. Moderate to 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).