The Pacific Northwest continues transitioning into an increasingly mild weather regime as we head toward the weekend. A warm front brings some light precipitation from Snoqualmie Pass northward early Friday morning. The front stalls closer to the Canadian border, enabling increasing moisture and SSW winds to wring out gradually increasing rain and higher elevation snow for the Mt Baker area as the day progresses. Further south, expect gradually warming temperatures within the warm sector. The one exception will be low elevations E of the Cascades, where low-level E flow will develop progressively a shallow cold air pool, complicating precipitation type near and east of the Cascade Passes once moisture rolls in.
In the afternoon, a cold front spreads increasing mostly light rain, snow, and areas of freezing rain into most of Washington State. This precipitation becomes moderate intensity with the frontal passage during the evening hours and then tapers to light post-frontal showers overnight into early Saturday.
The first wave of an atmospheric river brings increasing moderate SW winds along with the development of moderate to heavy rain and higher elevation snow for the Olympics and the northern Cascades in the afternoon. Snow levels rise to around 5500 to 7000 ft.
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
A few sprinkles or snow flurries in the morning, then increasing light rain and snow in the afternoon (moderate to heavy southern and eastern Olympics). Moderate ridgeline winds developing.
Friday
Night
Decreasing light rain and higher elevation snow showers.
Friday
Light rain and higher-elevation snow become moderate to heavy in the afternoon. Moderate to strong ridgeline winds.
Friday
Night
Moderate to heavy rain and snow become light and showery overnight.
Friday
A few sprinkles or snow flurries in the morning, then increasing light rain and snow in the afternoon.
Friday
Night
Moderate rain and snow become showery and light overnight.
Friday
Mostly cloudy and mild with a chance of light rain or higher elevation snow developing in the afternoon. Moderate ridgeline winds develop.
Friday
Night
Moderate rain and snow become mostly light overnight. Moderate ridgeline winds.
Friday
A few sprinkles or snow flurries in the morning, then increasing light rain, snow, or freezing rain increase in the afternoon. Light to occasionally moderate ridgeline and E wind at the Pass.
Friday
Night
Moderate rain, snow, and freezing rain become light and showery overnight.
Friday
A few sprinkles or snow flurries in the morning, then increasing light rain, snow, or freezing rain increase in the afternoon. Light to moderate ridgeline and E wind at the Pass.
Friday
Night
Moderate rain, snow, and freezing rain become light and showery overnight.
Friday
Increaisng periods of light snow.
Friday
Night
Decreasing light rain and snow becomes showery.
Friday
There will be a few sprinkles or snow flurries in the morning, followed by increasing light rain, snow, or freezing rain in the afternoon.
Friday
Night
Decreasing light rain, snow, and freezing rain become showery overnight.
Friday
Mostly cloudy with a slight chance of very light mixed precipitation in the afternoon.
Friday
Night
Decreasing light rain, snow, and freezing rain become showery overnight.
Friday
Mostly cloudy and mild. Moderate ridgeline winds develop in the afternoon.
Friday
Night
Decreasing light rain and higher elevation snow become showery overnight. 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).