A complex system will impact the region through the weekend. The weekend starts with a moisture-laden frontal system passing over the southern Puget Sound to Mt Baker and dropping SE. Out ahead of this front, expect heavy rain, high-elevation snow, and freezing rain at low elevations east of the Cascade Crest and through Snoqualmie Pass. Behind this front, ridgeline winds switch from SW to W and low-level pressure gradients switch W as well, switching freezing rain to rain at the Passes. A second frontal passage late Saturday will re-invigorate rain and snow through the afternoon as a converge band forms in the mountain loop late in the day then drops south toward Stevens Pass. It could impact Stevens for a long period during the evening and possibly the overnight hours.
Snow levels start dropping rapidly behind the initial frontal passage early Saturday, but they have a lot of ground to cover as they start around 9000 ft this morning. By the afternoon, they should be in the 4500 to 6500 ft range, dropping further to around 3000 ft overnight where they remain through Sunday.
An upper low brings the final act. This low will bring banded and locally heavy rain and snow as it drops SE into the region, overnight through Sunday. Precipitation should taper from N to south as the day progresses. This will bring 6-12" of snow to the west slopes of the Cascades.
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
Brief break in the rain and snow early, then light to occasionally moderate showers return. Strong cooling. Moderate ridgeline winds.
Saturday
Night
Light rain and snow showers become moderate overnight. Moderate ridgeline winds.
Saturday
Heavy rain and snow possibly becoming showery. Light ridgeline winds becoming moderate.
Saturday
Night
Light rain and snow become moderate to heavy overnight. Moderate ridgeline winds.
Saturday
Very heavy rain and snow. Moderate ridgeline winds.
Saturday
Night
Moderate rain and snow, locally very intense in convergence over the southern mountain loop or Highway 2 corridor. Moderate ridgeline winds.
Saturday
Heavy rain and snow at Paradise; moderate at Crystal and White Pass. Moderate ridgeline winds (strong near the Cascade Crest).
Saturday
Night
Light rain and snow becomes moderate to heavy overnight. Moderate ridgeline winds (strong near the Cascade Crest).
Saturday
Heavy rain and snow. Freezing rain ends by mid-morning. Strong cooling. Moderate ridgeline winds. Light E winds at the Pass switch W by mid-morning.
Saturday
Night
Light rain and snow in the evening (locally heavy in convergence) becomes moderate to heavy overnight. Moderate ridgeline winds with light to moderate W winds at the Pass.
Saturday
Heavy rain and snow. Freezing rain ends by mid-morning. Strong cooling. Moderate ridgeline winds. Light E winds at the Pass switch W by mid-morning.
Saturday
Night
Light rain and snow in the evening becomes moderate to heavy overnight. Moderate ridgeline winds with light to moderate W winds at the Pass.
Saturday
Heavy rain and freezing rain end by mid-morning, then light to moderate rain and snow showers through the end of the day. Moderate ridgeline winds.
Saturday
Night
Light to moderate snow showers. Moderate ridgeline winds.
Saturday
Heavy rain, freezing rain, and higher elevation snow. Moderate ridgeline winds with strong gusts.
Saturday
Night
Increasing light to moderate rain and snow showers. Moderate ridgeline winds with strong gusts.
Saturday
Heavy rain, freezing rain, and higher elevation snow. Moderate ridgeline winds with strong gusts.
Saturday
Night
Increasing light rain and snow showers. Moderate ridgeline winds with strong gusts.
Saturday
Increasing moderate to heavy rain and snow. Strong ridgeline winds.
Saturday
Night
Light to moderate rain and snow. 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).