We're in for a mixed bag of sun and clouds today as an upper trough spinning in the Gulf of Alaska slowly dips southward over the weekend. The upper level trough combined with increasing onshore westerly flow will bring a slight uptick in W-SW ridgeline winds along with some low clouds along the west slopes of the Cascades Saturday afternoon, especially near and north of I-90. We should see a few light showers develop over the northwest Cascades this afternoon with drier conditions elsewhere. Mid/lower mountain freezing levels/temperatures will be cooler than Friday but still mild, especially for central/southern areas and cooler to the NW.
We'll see more cooling Saturday night, with little change in the wind forecast or the placement of light showers. On Sunday, the upper trough will spin a more organized band of convective showers inland during the afternoon. Showers will increase and should become more intense along the west slopes of the Cascades and Passes by mid to late afternoon, with the slightly heavier precipitation holding off until the evening. W-SW winds will also increase Sunday afternoon. With the weekend's common theme, look for another dip in temperatures on Sunday as the cool upper trough nudges closer and exerts more influence over the region.
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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Saturday
A mix of sun and high clouds in the morning, becoming mostly cloudy in the afternoon with a slight chance of rain or snow showers. Light to occasionally moderate ridgeline winds.
Saturday
Night
Partly cloudy to mostly cloudy with a chance of light rain and snow showers. Light to moderate ridgeline winds.
Saturday
A mix of sun and high clouds in the morning, becoming mostly cloudy in the afternoon with a chance of rain or snow showers. Light to moderate ridgeline winds.
Saturday
Night
Mostly cloudy with scattered light rain and snow showers. Light to moderate ridgeline winds.
Saturday
A mix of sun and high clouds in the morning, becoming mostly cloudy in the afternoon with a slight chance of rain or snow showers. Light to occasionally moderate ridgeline winds.
Saturday
Night
Mostly cloudy with a chance of light rain and snow showers. Light to moderate ridgeline winds.
Saturday
A mix of sun and high clouds. Light to moderate ridgeline winds.
Saturday
Night
Partly cloudy to mostly cloudy. Moderate ridgeline winds.
Saturday
A mix of sun and high clouds in the morning, becoming mostly cloudy in the afternoon. Light to occasionally moderate W ridgeline and Pass level winds.
Saturday
Night
Mostly cloudy with a chance of light rain and snow showers. Light to moderate W ridgeline and Pass level winds.
Saturday
A mix of sun and high clouds in the morning, becoming mostly cloudy in the afternoon. Light to occasionally moderate W ridgeline and Pass level winds.
Saturday
Night
Mostly cloudy with a chance of light rain and snow showers. Light to moderate W ridgeline and Pass level winds.
Saturday
A mix of sun and high clouds. Light to moderate ridgeline winds.
Saturday
Night
Partly cloudy to mostly cloudy. Moderate ridgeline winds.
Saturday
Partly to mostly sunny with periods of high clouds and filtered sunshine. Light to moderate ridgeline winds.
Saturday
Night
Partly cloudy to mostly cloudy. Moderate ridgeline winds.
Saturday
Partly to mostly sunny with periods of high clouds and filtered sunshine. Light to moderate ridgeline winds.
Saturday
Night
Partly cloudy to mostly cloudy. Moderate ridgeline winds.
Saturday
Partly to mostly sunny with periods of high clouds and filtered sunshine. Light to moderate ridgeline winds.
Saturday
Night
Partly cloudy to mostly cloudy. 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).