A ridge of high pressure retains its grip on our region Wednesday and Wednesday night as the ridge axis shifts to our east. A deep upper low moves into our offshore waters on Wednesday. Upper-level high clouds out ahead of this low will move across our region on Wednesday, resulting in filtered sunshine across the region. Clouds will be slightly thicker over the Olympics and northwest Washington Cascades but expect plenty of solar radiation to come through. Temperatures started the day on Wednesday in the upper 20s and low 30s at most NWAC weather stations. The mild start combined with mild air moving in on increasing light S and SE ridgeline winds will allow freezing levels to push upward to 5500-6000 ft this afternoon.
Expect a shallow or minimal refreeze Wednesday night as freezing remain elevated. Ridgeline winds continue to increase as the eastward progression of the upper low moves a surface cold front into our near-shore waters.
The cold front arrives on Thursday, spreading bands of light rain and higher elevation snow into our mountains, particularly during the afternoon hours. We anticipate 1-3" of snow to fall above around 5000 ft, with snow levels dropping with the cold frontal passage very late in the day. S winds should peak during the morning in the moderate to occasionally strong range for areas exposed to this flow direction.
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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Wednesday
High clouds and filtered sunshine.
Wednesday
Night
Mostly clear with thin high clouds.
Wednesday
Mostly clear to start the day, then high clouds and filtered sunshine.
Wednesday
Night
Mostly clear with thin high clouds.
Wednesday
Mostly clear to start the day, then high clouds and filtered sunshine.
Wednesday
Night
Mostly clear with thin high clouds.
Wednesday
Thin high clouds and filtered sunshine.
Wednesday
Night
Mostly clear with thin high clouds.
Wednesday
Mostly clear to start the day, then high clouds and filtered sunshine. Light E winds at the Pass.
Wednesday
Night
Mostly clear with thin high clouds. Increasing light to moderate E winds at the Pass.
Wednesday
Mostly clear to start the day, then high clouds and filtered sunshine. Light E winds at the Pass.
Wednesday
Night
Mostly clear with thin high clouds. Increasing light to moderate E winds at the Pass.
Wednesday
Mostly clear to start the day with high clouds filtering the sunshine more in the afternoon.
Wednesday
Night
Mostly clear with thin high clouds.
Wednesday
Mostly clear to start the day with high clouds filtering the sunshine from mid-morning onwards.
Wednesday
Night
Mostly clear with thin high clouds.
Wednesday
Mostly sunny with high clouds filtering the sunshine at times.
Wednesday
Night
Mostly clear with thin high clouds.
Wednesday
Mostly sunny with high clouds filtering the sunshine at times.
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).