Snow(!) returns to the forecast as a north-to-south oriented frontal system pushes through western Washington this morning. Precipitation will continue to fill in over the west slopes of the Cascades and Passes as the front crosses the Cascades in the 8-10am window. Initially mild temperatures will cool quickly with the onset of precipitation. We'll likely see a little rain mix in at mid-elevations before precipitation intensity picks up and snow levels cool mid-day and further through the afternoon hours.
There's a good W-NW punch behind this frontal system. We can expect strong WNW winds, snow showers that favor the west slopes of the Cascades and a Puget Sound Convergence Zone (PSCZ). The PSCZ is likely to favor the Stevens and Mt Loop initially through the early afternoon and the Snoqualmie area late this afternoon through this evening. While this storm isn't a huge snow maker, the heaviest bands of post-frontal showers could give a few hours of more significant snowfall rates in the 1-2" hr range.
WNW winds and showers will slowly taper down Friday night as an upper level ridge builds offshore. We'll see some low clouds stuck mainly in the Passes and along the west slopes of the Cascades at least through the morning. We should see mostly to partly sunny skies Saturday afternoon with freezing levels around 2500-3000'.
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
Moderate rain and snow becoming light to occasionally moderate snow showers by late morning. Strong ridgeline winds.
Light to moderate rain and snow becoming light to moderate snow showers by mid-day. Strong ridgeline winds.
Friday
Night
Mostly cloudy with light to occasionally moderate snow showers becoming scattered overnight. Moderate ridgeline winds easing overnight.
Friday
Light to occasionally moderate rain and snow becoming light to occasionally moderate snow showers by mid-day. Strong ridgeline winds.
Friday
Night
Mostly cloudy with light to occasionally moderate snow showers becoming scattered overnight. Moderate ridgeline winds easing overnight.
Friday
Light to occasionally moderate rain and snow developing this morning. Becoming light to moderate snow showers by mid-day. Light E winds at Pass level in the morning then strong W ridgeline and Pass level winds.
Friday
Night
Mostly cloudy with light to moderate snow showers becoming scattered overnight. Moderate to strong WNW ridgeline and Pass level winds easing overnight.
Friday
Light to occasionally moderate rain and snow developing this morning. Becoming light to moderate snow showers by mid-day. Light E winds at Pass level in the morning then strong W ridgeline and Pass level winds.
Friday
Night
Mostly cloudy with light to moderate snow showers becoming scattered late. Moderate to strong WNW ridgeline and Pass level winds easing overnight.
Friday
Cloudy with light rain and snow developing late morning. Light to occasionally moderate snow showers near the Cascade crest in the afternoon. Strong ridgeline winds.
Friday
Night
Scattered snow showers near the Cascade crest in the evening becoming partly cloudy late. Strong ridgeline winds easing overnight.
Friday
Cloudy with light rain and snow developing late morning. Light to occasionally moderate snow showers near the Cascade crest in the afternoon. Strong ridgeline winds.
Friday
Night
Scattered snow showers near the Cascade crest in the evening, heaviest downwind of Stevens and Snoqualmie Passes. Becoming partly cloudy late. Strong ridgeline winds easing overnight.
Friday
Cloudy with light rain and snow developing late morning. Light to occasionally moderate snow showers near the Cascade crest in the afternoon. Strong ridgeline winds.
Friday
Night
Scattered snow showers near the Cascade crest in the evening becoming partly cloudy late. Strong ridgeline winds easing overnight.
Friday
Cloudy with light rain and snow. Light to occasionally moderate snow showers in the afternoon. 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).