A sharp cold front pushed through the Cascades Sunday night, leaving an unstable air mass moving in on a brisk W and WNW flow. Rapid cooling occurred behind the front from 4-7 AM with snow levels dropping to 1500-2000 ft for most of the region and should remain at these levels most of the day. An organized band of moderate to heavy precipitation is moving into the Cascades early this morning with moderate to heavy snowfall with plenty of closed convective showers upstream and moving into the Olympics. This will keep light to moderate (and in a few locations heavy) snow showers continuing across the region throughout the day. The heaviest snow will be focused on convergence bands which start in the mountain loop, but may drift throughout the Central Cascades region throughout the day and into the evening hours. Expect strong ridgeline winds to continue through the evening in exposed locations near and east of the Cascade Crest, such as White Pass, Crystal, Mission Ridge, and Mt. Hood.
Snow showers and convergence gradually ramp down Monday night in concert with decreasing ridgeline winds. A closed circulation center within the upper trough drifts over southern Washington into northern Oregon early Tuesday, perhaps bringing an uptick one final wave of moisture for the southern Cascades before upper-level winds turn N or NE by mid-morning on Tuesday and snow showers wind down with mostly sunny skies expected across the region by the afternoon.
Expect high snow ratios with the cold temperatures. Mt Baker could pick up an additional 3-6", and the central Washington Cascades, Paradise, and Mt Hood upwards of 1 ft before the snowfall ends.
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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Monday
Decreasing light to moderate snow showers.
Monday
Night
Decreasing light snow showers.
Monday
Moderate snow showers becoming light.
Monday
Night
Decreasing light snow showers.
Monday
Moderate snow showers, heavy at times in convergence from the Mountain Loop southward.
Monday
Night
Moderate snow showers and convergence in the evening, becoming light overnight.
Monday
Moderate to heavy snow showers at Paradise. Light to moderate snow showers at Crystal and White Pass. Strong ridgeline winds near the Cascade Crest.
Monday
Night
Light snow showers (moderate at Paradise) in the evening, becoming universally light and decreasing overnight. Strong ridgeline winds near the Cascade Crest decreasing overnight.
Monday
Increasing moderate snow showers, locally heavy in convergence. Moderate ridgeline and light to moderate W wind at the Pass.
Monday
Night
Decreasing light snow showers. Moderate ridgeline and W wind at the Pass becoming light.
Monday
Increasing moderate snow showers, locally heavy in convergence. Moderate ridgeline and W wind at the Pass. Strong ridgeline winds in exposed areas and strong gusts.
Monday
Night
Decreasing moderate snow showers becoming. Moderate ridgeline and W wind at the Pass becoming light.
Monday
Decreasing light snow showers. Strong ridgeline winds in exposed areas and strong gusts.
Monday
Night
Light snow showers tapering in the evening, with mostly cloudy skies overnight.
Monday
Light to moderate snow showers and convergence spillover Western Part; light further east. Strong ridgeline winds in exposed areas and strong 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).