A strong frontal system dropped south overnight, delivering feet of snow to many locations and making the end of February a memorable one. The front has become more north-south oriented and will continue to weaken this morning, with the dregs of steadier (stratiform) precipitation over CA/OR and extending up to the central WA Cascades. Scattered showers can be found further north and west, with heavier banding aimed into the northwest Cascades. Strong to extreme SW winds that occurred overnight have begun to ease and will remain in the moderate range today, except locally strong down at Mt Hood. We'll likely see a lull in shower activity for most areas late morning through early afternoon but with a cold and unstable airmass setting up overhead, we should expect showers to increase especially along the west slopes of the Cascades during the afternoon hours and extending through the evening. Heavier showers are likely to contain graupel. Snow levels will sit around 1500-2000' this afternoon during showers. More sunbreaks east of the Cascade crest will help afternoon freezing levels pop up to 3000-3500'. Snow levels will dip to 0-1000' overnight.
A cold upper level trough offshore will be the main weather feature over the next few days. A shortwave trough will rotate up from the south overnight, reinvigorating showers and ridgeline winds overnight. Friday looks similar but with another upper level disturbance and daytime heating providing a helping hand to increase shower coverage. This pattern will provide fresh shots of low density snow every 12 hrs, with the higher amounts likely along the west slopes of the Cascades, the Olympics and the Mt Hood area.
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
Mostly cloudy with light to occasionally moderate snow showers. Heaviest accumulations southwest slopes of the Olympics. Ridgeline winds becoming moderate in the afternoon.
Thursday
Night
Mostly cloudy with light to occasionally moderate snow showers. Heaviest accumulations southwest slopes of the Olympics. Moderate ridgeline winds becoming strong overnight.
Thursday
Moderate snow showers this morning becoming mostly cloudy with light to occasionally moderate snow showers this afternoon. Ridgeline winds becoming moderate in the afternoon.
Thursday
Night
Light to moderate snow showers. Moderate ridgeline winds.
Thursday
Light to occasionally moderate snow this morning, becoming light scattered showers late morning. Showers increasing again in the afternoon. Moderate ridgeline winds.
Thursday
Night
Light to occasionally moderate snow showers. Moderate ridgeline winds.
Thursday
Light to occasionally moderate snow this morning, becoming light scattered showers late morning. Showers increasing again in the afternoon. Moderate ridgeline winds increasing in the afternoon.
Thursday
Night
Light to occasionally moderate snow showers. Moderate to strong ridgeline winds.
Thursday
Light to occasionally moderate snow this morning, becoming light scattered showers late morning. Showers increasing again in the afternoon. Moderate ridgeline and Pass level W winds easing in the afternoon.
Thursday
Night
Mostly cloudy with light to occasionally moderate snow showers. Light east winds at Pass level, light to moderate S-SW winds at ridgeline.
Thursday
Light to occasionally moderate snow this morning, becoming light scattered showers late morning. Showers increasing again in the afternoon. Moderate ridgeline and Pass level W winds easing in the afternoon.
Thursday
Night
Mostly cloudy with light to occasionally moderate snow showers. Light east winds at Pass level, light to moderate S-SW winds at ridgeline.
Thursday
Mostly cloudy with light to occasionally moderate snow showers this morning, becoming scattered light showers mid-day. Moderate ridgeline winds easing in the afternoon.
Thursday
Night
Mostly cloudy with scattered light to occasionally moderate snow showers. Light to moderate ridgeline winds
Thursday
Light to occasionally moderate snow this morning, becoming mostly cloudy with light scattered showers late morning and afternoon sunbreaks. Moderate ridgeline winds.
Thursday
Night
Mostly cloudy with scattered light to occasionally moderate snow showers. Moderate ridgeline winds
Thursday
Light to occasionally moderate snow this morning, becoming mostly cloudy with light scattered showers late morning and afternoon sunbreaks. Moderate ridgeline winds.
Thursday
Night
Mostly cloudy with scattered light to occasionally moderate snow showers. Moderate ridgeline winds
Thursday
Light to moderate snow becoming showers mid-day. Moderate to strong ridgeline winds.
Thursday
Night
Light to occasionally 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).