A short-lived ridge over the area will maintain dry conditions on Wednesday. Gradually thickening high clouds ahead of a slow-moving offshore frontal system will bring filtered sunshine to most areas during the morning hours with skies gradually becoming obscured during the afternoon. Light rain reaches the coast late in the day. Expect increasing mostly light ridgeline winds which could increase into the moderate range at times for Mt Hood, Mt St Helens, and Mt Baker. Freezing levels rise to around 3500-4000 ft after a chilly start with below-freezing temperatures down to valley bottoms.
Light rain and snow spread from SW to NE across much of the region Wednesday night. Snow levels continue to slowly rise in the 3500-4500 ft range. SSW winds continue to increase in the light to moderate range as low-level E flow develops through the mountain gaps.
A shortwave catches up to the stalled offshore frontal system and re-invigorates it on Thursday. Expect moderate SSW winds to focus more of the light to moderate rain and snow on the Cascades volcanoes with the pattern keeping precipitation very light through the mountain gaps where E flow increases into the moderate range at times by the afternoon. Snow levels rise to 4000-5000 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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Wednesday
High clouds lowering and thickening. Filtered sunshine in the morning, then obscured skies from late morning onwards.
Wednesday
Night
Milder with light rain and snow developing in the evening and increasing overnight.
Wednesday
Scattered low clouds early, then filtered sunshine through the morning with high clouds lowering and thickening during the afternoon.
Wednesday
Night
Cloudy in the evening with light rain and snow developing. Increasing moderate ridgeline winds.
Wednesday
Scattered low clouds early, then filtered sunshine through the morning with high clouds lowering and thickening during the afternoon.
Wednesday
Night
Cloudy in the evening with light rain and snow developing in the early morning hours.
Wednesday
Scattered low clouds early, then filtered sunshine through the morning with high clouds lowering and thickening during the afternoon.
Wednesday
Night
Light rain and snow develop during the evening hours and increase overnight.
Wednesday
Scattered low clouds early, then filtered sunshine through the morning with high clouds lowering and thickening during the afternoon. Light ridgeline and W wind at the Pass.
Wednesday
Night
Cloudy in the evening with light rain and snow developing in the early morning hours. Light ridgeline and increasing E wind at the Pass.
Wednesday
Scattered low clouds early, then filtered sunshine through the morning with high clouds lowering and thickening during the afternoon. Light ridgeline and W wind at the Pass.
Wednesday
Night
Cloudy in the evening with light rain and snow developing in the early morning hours. Light ridgeline and increasing E wind at the Pass.
Wednesday
Filtered sunshine through the early afternoon with high clouds lowering and thickening late in the day.
Wednesday
Night
Cloudy.
Wednesday
Filtered sunshine through the morning with high clouds lowering and thickening during the afternoon.
Wednesday
Night
Cloudy.
Wednesday
Filtered sunshine through the morning with high clouds lowering and thickening during the afternoon.
Wednesday
Night
Cloudy in the evening with light snow possibly developing overnight.
Wednesday
High clouds lowering and thickening.
Wednesday
Night
Increasing light to occasionally moderate rain and snow. Increasing 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).