A deep, but filling closed upper low presents as a picturesque spiral of clouds in the PNW offshore waters. As the upper low approaches the coastline, an upper-level front brings a weakening rain band over the region from SW to NE during the morning through mid-day hours. The rain band should become less continuous as the day progresses and should deliver the most precipitation to the Olympics. The second band of light to moderate precipitation associated with a surface cold front moves into the Olympics Thursday afternoon and into the Cascades from the late afternoon through evening hours. Behind the front, snow levels drop and precipitation becomes light and scattered snow showers. Elevations above 5000 ft in Cascades and Olympics could see 1-3" of snow during the day Thursday with an additional 2-4" possible Thursday night down to 4000 ft.
Additional bands of rain and snow arrive as the weakening upper low moves into the near-shore waters on Friday. Snow levels should fluctuate around 2500-3500 ft with convective showers becoming increasingly common during the afternoon hours.
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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Thursday
An initial band of light to occasionally moderate rain and snow arrives during the morning hours. Another band of rain and snow likely arrives during the afternoon.
Thursday
Night
Cooler with light rain and snow showers.
Thursday
Periods of light rain and snow from mid-morning onwards.
Thursday
Night
Light to moderate rain and snow during the evening, then becoming showery. Cooler.
Thursday
Periods of light rain and snow from mid-morning onwards.
Thursday
Night
Light to moderate rain and snow during the evening, then becoming showery. Cooler.
Thursday
Periods of light rain and snow from mid-morning onwards, likely increasing late in the day.
Thursday
Night
Light to occasionally moderate rain and snow during the evening, then becoming showery. Cooler.
Thursday
Periods of light rain and snow from mid-morning onwards.
Thursday
Night
Light to occasionally moderate rain and snow during the evening, then becoming showery. Cooler.
Thursday
Periods of light rain and snow from mid-morning onwards.
Thursday
Night
Light to occasionally moderate rain and snow during the evening, then becoming showery. Cooler.
Thursday
Periods of light rain and snow during the afternoon.
Thursday
Night
Light to occasionally moderate rain and snow during the evening, then becoming showery. Cooler.
Thursday
Periods of light rain and snow from late-morning onwards.
Thursday
Night
Light to occasionally moderate rain and snow during the evening, then becoming showery. Cooler.
Thursday
Periods of light rain and snow from mid-morning onwards.
Thursday
Night
Light rain and snow during the evening, then becoming showery. Cooler.
Thursday
Mostly cloudy with a slight chance of rain or snow in the morning. Light rain and snow increasing during the late afternoon hours.
Thursday
Night
Periods of light rain and snow during the evening hours tapering to snow flurries. Cooler.
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).