A stream of moisture rounds over the top of an expanding offshore ridge, taking the form of a warm front as it impacts the Pacific Northwest Friday through Saturday. Periods of light rain and snow will increase throughout the day on Friday, with moderate rain and snow possible from Mt Rainier to the Mountain Loop, including the passes. Snow levels start around 3000 ft and gradually rise to 5000-7000 ft by the end of the day, with the Olympics warming the most. The moisture and clouds continue to stream in from the NW, but increasing light-to-moderate ridgeline winds are generally westerly. The flow pattern could favor areas along the northern edge of the Olympics, while Mt Baker is less favored than usual.
Rain and higher-elevation snow peaks on Friday evening, then gradually decreases overnight. Meanwhile, ridgeline winds continue to ramp up in the moderate range for areas near and east of the Cascade Crest.
By Saturday morning, snow levels hover around 8000 ft in most areas, and the area generally resides in a somewhat drier "warm sector" of the storm as the high pressure exerts influence. Areas south of I-90 will be drier than areas further north. But clouds will linger over most of the region. Expect snow levels to drop to around 7000 ft in the afternoon.
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
Increasing periods of light to moderate rain and snow. Rising snow levels.
Friday
Night
Decreasing light rain and higher elevation snow become showery overnight. Moderate ridgeline winds peak in the evening hours.
Friday
Increasing periods of generally light rain and snow. Rising snow levels.
Friday
Night
Light to moderate rain and higher-elevation snow decrease overnight. Rising snow levels. Moderate ridgeline winds near the Cascade Crest.
Friday
Increasing periods of generally light rain and snow. Rising snow levels. Moderate ridgeline winds near the Cascade Crest.
Friday
Night
Light to moderate rain and higher-elevation snow decrease overnight. Rising snow levels. Moderate ridgeline winds near the Cascade Crest.
Friday
Increasing periods of light to moderate rain and snow. Rising snow levels. Moderate ridgeline winds near the Cascade Crest.
Friday
Night
Light to moderate rain and higher-elevation snow (heaviest at Paradise) decrease overnight. Rising snow levels. Moderate ridgeline winds near the Cascade Crest.
Friday
Increasing periods of light to moderate rain and snow. Rising snow levels. Light to moderate ridgeline and generally light W wind at the Pass.
Friday
Night
Moderate rain and higher elevation snow decreases overnight. Rising snow levels. Increasing moderate ridgeline winds and generally light W wind at the Pass.
Friday
Increasing periods of light to moderate rain and snow. Rising snow levels. Light to moderate ridgeline and generally light W wind at the Pass.
Friday
Night
Moderate rain and higher elevation snow decreases overnight. Rising snow levels. Increasing moderate ridgeline winds and light to moderate W wind at the Pass.
Friday
Increasing periods of light rain and snow. Rising snow levels. Light to moderate ridgeline winds.
Friday
Night
Periods of light rain and higher elevation snow. Rising snow levels. Moderate ridgeline winds.
Friday
Increasing periods of light rain and snow. Rising snow levels. Light to moderate ridgeline winds.
Friday
Night
Periods of light rain and higher elevation snow. Rising snow levels. Moderate ridgeline winds.
Friday
Increasing periods of light rain and snow. Rising snow levels. Light to moderate ridgeline winds.
Friday
Night
Periods of light rain and higher elevation snow. Rising snow levels. Moderate ridgeline winds.
Friday
Increasing periods of light rain and snow. Rising snow levels. Moderate ridgeline winds, strong gusts.
Friday
Night
Periods of generally light rain and higher elevation snow. Rising snow levels. Moderate to 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).