High pressure departs the region as a cutoff low drifting southward off the Alaskan Panhandle rotates an initial shortwave feature toward the British Columbia Coastline. The shortwave should brush the Olympics and Cascades West North zone with a slight chance of a sprinkle, but most areas remain dry. Thinner high clouds and partly to mostly sunny conditions should be replaced by mostly cloudy skies for the west slopes of the Washington Cascades by the end of the day on Thursday. The shortwave will also bring gradually cooling temperatures during the day and breezy conditions (light to moderate WSW winds). Mt. Hood remains the warmest, although freezing levels lower here too from 9500 ft to 8500 ft during the day.
Thursday night, the weak frontal feature associated with the aforementioned shortwave arrives, bringing an increased chance of very light rain or snow from Snoqualmie Pass northward, but we don't expect substantial accumulations.
A chance of very light rain or snow showers lingers into the morning hours on Friday for the west slopes of the Washington Cascades. Expect partly to mostly cloudy skies banked up against the west slopes of the Cascades with clearer skies further east. Temperatures should be cooler than Thursday with 3000-6000 ft snow levels.
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
Mostly cloudy.
Thursday
Night
Partly cloudy to mostly clear skies.
Thursday
Mostly cloudy.
Thursday
Night
Mostly cloudy with a chance of very light rain or snow.
Thursday
Partly to mostly sunny, then becoming mostly cloudy by mid-afternoon.
Thursday
Night
Mostly cloudy with a chance of very light rain or snow.
Thursday
High clouds giving way to mostly sunny skies during the mid-day hours with clouds returning late in the day.
Thursday
Night
Mostly cloudy skies in the evening with clearing skies overnight.
Thursday
Some high clouds early, then mostly clearing skies. Mostly cloudy skies late in the day.
Thursday
Night
Partly to mostly cloudy.
Thursday
High clouds early, then becoming mostly sunny with clouds increasing again late in the day.
Thursday
Night
Mostly cloudy, then becoming partly cloudy.
Thursday
Partly cloudy to mostly sunny skies.
Thursday
Night
Partly cloudy.
Thursday
High clouds early, then becoming mostly sunny.
Thursday
Night
Mostly cloudy in the evening, with mostly clear skies overnight.
Thursday
High clouds early, then becoming mostly sunny.
Thursday
Night
Mostly cloudy in the evening, with mostly clear skies overnight.
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).