Our final major upper-level disturbance in NW flow has started to bring moderate snowfall to the Cascades from I-90 to the Candian border. The rain and snow should intensify in the same areas and expand southward as the day progresses as the surface low tracks down the British Columbia coastline. Snow levels along the west slopes of the Cascades should rise from 2000 ft this morning and peak in the 3000-3500 ft range. Accelerating down-slope winds are warmer along the east slopes of the Cascades, leading to snow levels around 500 ft higher east of the mountains. We expect around 8-12" of snow above 3500 ft from Snoqualmie Pass to Mt. Baker by the end of the day on Saturday with 6-8" for White Pass and Paradise.
Postfrontal moderate snowfall should focus on the central Washington Cascades Saturday night as snow levels lower. Strong convergence bands could create intense snowfall rates and snowfall amounts in the 4-8" range from Snoqualmie Pass to the Mountain Loop area overnight.
The snow will gradually decrease, but the same areas of the central Cascades should pick up another 2-8" of low-density snow on Sunday.
This system will be very windy throughout with moderate to strong ridgeline winds across a wide area. The strongest winds will be east of the Cascades and through mountain gaps Saturday and Saturday night with strong to extreme likely for the Wenatchee Mountains and White Pass. The winds should gradually ease on Sunday.
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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Saturday
Light snow, heaviest during the mid-morning hours.
Saturday
Night
Mostly cloudy with light snow showers possible.
Saturday
Heavy snow. Moderate to strong ridgeline winds.
Saturday
Night
Mostly cloudy with periods of light snow or snow showers.
Saturday
Heavy rain and snow. Moderate to strong ridgeline winds peaking in the afternoon.
Saturday
Night
Moderate snow, heaviest in convergence. Gradually decreasing moderate to strong ridgeline winds.
Saturday
Moderate to heavy rain and snow developing at Paradise and White Pass with light rain and snow at Crystal. Very strong to extreme ridgeline winds near White Pass. Elsewhere, ridgeline winds will be strong.
Saturday
Night
Light snow showers, heaviest at Paradise. Decreasing moderate to strong ridgeline winds in most locations. Very strong ridgeline winds continue, but gradually decreasing near White Pass.
Saturday
Heavy rain and snow. Moderate to strong ridgeline winds peaking in the afternoon. Moderate W winds at the Pass.
Saturday
Night
Moderate snow, locally heavy in convergence bands. Moderate to strong ridgeline winds. Decreasing light to moderate W winds at the Pass.
Saturday
Heavy rain and snow. Moderate to strong ridgeline winds peaking in the afternoon. Moderate W winds at the Pass.
Saturday
Night
Moderate snow, locally heavy in convergence bands. Moderate to strong ridgeline winds. Decreasing moderate W winds at the Pass.
Saturday
Moderate rain and snow. Moderate to strong ridgeline winds.
Saturday
Night
Light snow showers. Moderate to strong ridgeline winds.
Saturday
Moderate to heavy rain and snow western part, lighter further east. Strong ridgeline winds.
Saturday
Night
Moderate snow showers western part, lighter further east. Strong ridgeline winds.
Saturday
Light snow. Moderate to strong ridgeline winds.
Saturday
Night
Light snow showers. Moderate to strong ridgeline winds.
Saturday
Light rain and snow developing in the morning, potentially becoming moderate in the afternoon. Strong to very strong ridgeline winds with extreme gusts.
Saturday
Night
Light rain and snow showers. Strong to very strong ridgeline winds with extreme gusts.
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).