A long-duration atmospheric river will have its final impacts this morning, with high elevation rain and warm temperatures persisting across the Cascades. The heaviest precipitation has been focused on the western front, from Mt Rainier to Mt Baker, while southern areas near Mt Hood stayed mostly dry. Snow levels are still well above the upper elevations.
Precipitation will continue through Friday afternoon as a surface low moves inland over British Columbia. The heaviest amounts are expected north of I-90, with decent spill over east of the Cascade Crest. A convergence zone will set up late Friday afternoon over the mountain loop area, bringing locally heavier rain and high elevation snow into the evening hours.
A cold air mass will move into the region Friday evening, as precipitation tapers, and long-awaited snowfall returns to the upper elevations. By Saturday morning, snow levels will drop to near the height of most mountain passes, but there won't be much moisture left over for snow production. There's a chance of some light snowfall early in the day, but it won't add up to much. Westerly flow takes over through the day, as cloud cover moves out, and winds moderate at ridgeline.
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
Moderate rain and highest elevation snow. Moderate ridgeline wind.
Friday
Night
Mostly cloudy.
Friday
Heavy rain and highest elevation snow. Moderate ridgeline wind.
Friday
Night
Occasional light rain and mountain snow. Light to moderate ridgeline wind.
Friday
Heavy rain and highest elevation snow. Light to moderate ridgeline wind.
Friday
Night
Light rain and mountain snow. Light to moderate ridgeline wind.
Friday
Rain and high elevation snow. Heavier rain around the Paradise area. Moderate to strong ridgeline wind.
Friday
Night
Rain and mountain snow, with the heaviest precipitation around the Paradise area. Light to moderate ridgeline wind.
Friday
Moderate to heavy rain. Moderate ridgeline and light wind at the Pass.
Friday
Night
Light rain and mountain snow. Light to moderate ridgeline and Pass level wind.
Friday
Moderate to heavy rain. Moderate ridgeline and Pass level wind.
Friday
Night
Light rain and mountain snow. Light to moderate ridgeline and Pass level wind.
Friday
Moderate to heavy rain and highest elevation snow. Moderate ridgeline wind.
Friday
Night
Occasional light snow. Moderate ridgeline wind.
Friday
Light rain and highest elevation snow. Moderate to strong ridgeline wind.
Friday
Night
Occasional light rain and mountain snow. Moderate to strong ridgeline wind.
Friday
Light rain. Moderate ridgeline wind.
Friday
Night
Occasional light rain and mountain snow.
Friday
Building clouds, with light rain and high elevation snow in the afternoon. Moderate to strong ridgeline wind.
Friday
Night
Light rain and mountain snow. Moderate to strong ridgeline wind.
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).