Cooler air has moved into the region in the wake of Tuesday evening's strong cold frontal passage. This has lowered snow levels to around 2000 ft in the north, 3000 ft in the Snoqualmie Pass area and the southern Washington Cascades, and 3500-4000 ft for Mt Hood. With a trough centered just offshore, light to moderate SW ridgeline winds will continue to maintain mostly cloudy skies and light snow showers for areas near and west of the Cascade Crest through the morning hours. A secondary cold front will bring a period of increased S winds, moderate snowfall, followed by a push of W winds in its wake. This will impact the Olympics in the late morning or mid-day hours and the Cascades in the mid-to-late afternoon hours.
The westerly wind push initiates a convergence band from late Wednesday through the evening hours in the mountain loop area, dropping south to around Stevens Pass, likely fizzling overnight in this vicinity. This system could bring a quick 4-8" of snow from Mt Baker to Stevens Pass, while other areas can expect 1-3" of snow. Although snow levels remain relatively steady on Wednesday, they should drop rapidly, bottoming out around 500 ft as snow shower activity dissipates and retreats northward Thursday morning. Some models indicate just enough afternoon convection to keep snow shower activity going in the Olympics and Mt Baker areas.
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 snow showers with a period of moderate snowfall likely in the late morning hours.
Wednesday
Night
Decreasing light snow showers. Moderate ridgeline winds in the evening hours.
Wednesday
Light to moderate snow showers with a period of moderate to heavy snow in the afternoon. Moderate ridgeline winds.
Light snow showers in the morning, then moderate to heavy snow in the afternoon. Moderate ridgeline winds.
Wednesday
Night
Decreasing light to moderate snow showers (locally heavy in convergence trending southward from the mountain loop). Moderate ridgeline winds near the Cascade Crest.
Wednesday
Occasional light rain and snow showers in the morning, then several hours of moderate snow in the afternoon. Moderate ridgeline winds, increasing late in the day.
Wednesday
Night
Decreasing mostly light snow showers. Decreasing moderate ridgeline winds may be strong at times in the evening.
Wednesday
Light snow showers in the morning with a period of moderate snowfall in the afternoon. Moderate ridgeline and mostly light W wind at the Pass both increase late in the day.
Wednesday
Night
Decreasing light to moderate snow showers, locally heavy in convergence banding. Decreasing moderate ridgeline and light to moderate W wind at the Pass.
Wednesday
Light rain and snow showers in the morning, with a period of moderate snowfall in the afternoon. Moderate ridgeline and light-to-moderate W wind at the Pass both increase late in the day.
Wednesday
Night
Decreasing light to moderate snow showers, with a slight chance of convergence enhancement. Decreasing moderate ridgeline. Moderate W wind at the Pass decreases to the light-to-moderate range overnight.
Wednesday
Light snow showers in the morning with a brief period of moderate snow late in the day. Light to moderate ridgeline winds increase late in the day.
Occasional light snow showers in the morning with a brief period of steadier snowfall in the afternoon. Moderate ridgeline winds increase late in the day.
Wednesday
Night
Decreasing light snow showers primarily near the Cascade Crest. Decreasing moderate ridgeline winds.
Wednesday
Occasional light snow showers in the morning with a brief period of steadier snowfall in the afternoon. Moderate ridgeline winds increase late in the day.
Wednesday
Night
Decreasing light snow showers primarily near the Cascade Crest. Decreasing moderate ridgeline winds.
Wednesday
Occasional light rain and snow showers in the morning, with a period of steadier snowfall in the afternoon. Moderate to strong ridgeline winds.
Wednesday
Night
Decreasing light snow showers. Moderate to strong ridgeline winds decrease fully into the moderate range.
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).