We're in the final phase of a massive storm that has impacted the Pacific Northwest since Wednesday. An upper-level front crossed the Cascades early this morning, bringing the heaviest rain and snow with it. However, the surface low lags behind and should cross the southern Washington Cascades by mid-morning. As it progresses, expect moderate to heavy rain and snow to the west of the Cascade Crest, with WSW continuing to over-run low-level entrenched cold air creating a wintry mix to the east other Cascade Crest. A push of strong W winds from mid-morning onward should help to scour out the cold air east of the Cascade Crest, while bringing in cold air aloft, lowering snow levels. Ridgeline winds will remain in the strong range throughout the day for places like White Pass, Mission Ridge, Crystal Mountain and Mt. Hood. Snowfall should turn showery and decrease during the afternoon, but convergence in the Snoqualmie to Stevens Pass vicinity should keep some heavy snowfall going. The latest model runs have shifted these heavier bands southward increasingly toward Snoqualmie Pass. Both passes can expect in the range of 8-14" of snow above 4000 ft on Friday.
Snow shower and more moderate convergence activity continue to decrease as snow levels continue to plummet Friday night. Expect several more inches of snow to fall with gradually decreasing WNW winds.
A weak front passing to our north on Saturday will bring a slight uptick in snow shower activity on Saturday afternoon, with snow levels well below the passes. Ridgeline winds should continue to decrease into the light to occasionally moderate range.
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
Very light rain or snow showers. Rapid cooling. Otherwise cloudy with a few sun breaks possible in the afternoon.
Friday
Night
Scattered light snow showers.
Friday
Moderate snow early, tapering to light snow showers by the afternoon. Cooling temperatures.
Friday
Night
Light snow showers.
Friday
Heavy rain and snow in the morning, tapering to light to moderate snow showers by the afternoon. Cooler. Heavier snow may persist longer in convergence bands.
Friday
Night
Light snow showers (moderate in convergence).
Friday
Heavy rain and snow at paradise, moderate rain and snow at White Pass, and light rain and snow at Crystal, all tapering to light snow showers in the afternoon. Strong ridgeline winds at White Pass and Crystal.
Friday
Night
Light snow showers. Strong ridgeline winds at White Pass and Crystal.
Friday
Heavy rain, freezing rain or snow in the morning, decreasing in the afternoon and changing to all snow, but remaining heavy in convergence bands. Cooling temperatures. Variable winds switching to moderate W at the Pass.
Friday
Night
Decreasing light snow showers (moderate in convergence).
Friday
Heavy rain, freezing rain or snow in the morning, decreasing in the afternoon and changing to all snow, but remaining heavy in convergence bands. Cooling temperatures. Variable winds switching to moderate W at the Pass.
Friday
Night
Decreasing light snow showers (moderate in convergence).
Friday
Light to moderate snow tapering to light snow showers.
Friday
Night
Mostly cloudy with very light snow showers near the Cascade Crest.
Friday
Moderate snow, freezing rain, and rain, decreasing and changing to light snow showers (moderate in convergence) by 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).