A long-duration storm system continues to impact the region through the Holiday weekend. Although the primary front moved through, brisk WSW winds continue to feed moderate rain and snow showers into the area as an upper low drifts toward the region. Snow levels range from 3500-5000 ft west of the Cascade Crest, while cold air remaining E of the Cascades keeps the east slopes and passes significantly colder. This also allows precipitation to spill over onto the east slopes of the Cascades, but spillover should gradually decrease.
A secondary feature targets the southern Cascades Sunday night with moderate to heavy rain and snow (light to moderate further north). Upper levels cool slightly, but as E flow gradually decreases low levels near the Cascade Crest may continue to moderate.
Low-level E flow gradually shifts W on Monday as the upper low moves onshore and becomes a trough. Light to moderate snow showers decrease and focus on the west slopes of the Cascades. Snow levels rise from 2500-3500 ft for the Cascade passes, likely shifting Snoqualmie Pass proper to rain.
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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Sunday
Light rain and snow showers.
Sunday
Night
Decreasing light rain and snow showers.
Sunday
Moderate rain and snow become light and scattered rain and snow showers by the afternoon. Moderate ridgeline winds early in the day.
Sunday
Night
Decreasing light rain and snow showers.
Sunday
Decreasing moderate rain and snow showers.
Sunday
Night
Light to moderate snow showers.
Sunday
Moderate rain and snow showers (light at Crystal). Light to moderate ridgeline winds focus on the ridgeline winds.
Sunday
Night
Moderate to locally heavy rain and snow showers.
Sunday
Decreasing moderate rain and snow showers. Light to occasionally moderate ridgeline. Gradually decreasing light E winds at the Pass.
Sunday
Night
Moderate rain and snow showers. Light ridgeline and E wind at the Pass may shift W temporarily at times.
Sunday
Decreasing moderate snow showers may mix with rain at 3000 ft and below late in the day. Light to moderate ridgeline and E wind at the Pass.
Sunday
Night
Moderate rain and snow showers. Light ridgeline and E wind at the Pass may shift W temporarily at times.
Sunday
Decreasing light snow showers.
Sunday
Night
Decreasing light snow showers.
Sunday
Decreasing light to snow showers. Moderate ridgeline winds at times.
Sunday
Night
Mostly light snow showers.
Sunday
Light rain and snow showers. Moderate ridgeline winds at times.
Sunday
Night
Mostly light rain and snow showers.
Sunday
Moderate rain and snow showers. Moderate ridgeline winds.
Sunday
Night
Moderate rain and snow showers. Moderate 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).