915 Update: Increased precipitation amounts for White Pass and Tieton R - Darland Mt today and updated today's weather for West South/East South.
A cold upper level trough continues to keep cooler than normal temperatures, light to moderate E-SE winds, and scattered showers over our region today. An organized E-W band of showers north of Hwy 12 should fizzle out this morning. Light easterly upslope will continue with broken to overcast skies and occasional light snow showers up and down the east slopes of Cascades today. The Olympics and areas west of the Cascade crest will see showers and convective clouds bubble up once again in the afternoon, drift from SE to NW, and continue through the evening hours. Heavier showers may contain graupel. Breezy but not strong E-SE ridgeline winds are expected over large portions of the Washington Cascades today. The northwest and central-west Cascades will benefit from some downsloping/drying, with the best chance of extended sunshine this morning and slightly milder temperatures/freezing levels versus the rest of the area.
Scattered showers this evening should start to fizzle out overnight. A more organized band of showers may move from south to north along the eastern slopes of the Cascades, producing some enhanced light snow accumulations. On Thursday, the upper low offshore will begin to merge with the jet stream that's been more active to our south and directing copious amounts of moisture into California. There's high confidence that E-SE ridgeline winds will increase during the day on Thursday, becoming strong in the afternoon and even stronger Thursday night. Light upslope snows should also increase along the east slopes of the Cascades on Thursday. There's low confidence regarding when light warm frontal precipitation will begin to make an appearance over northern Oregon and the southwest Cascades. That may not happen until Thursday night or Friday morning as new low pressure system develops.
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
Partly to mostly cloudy with scattered light snow showers in the morning, becoming mostly cloudy with scattered showers in the afternoon.
Wednesday
Night
Mostly cloudy with scattered light snow showers.
Wednesday
Partly to mostly sunny in the morning, becoming mostly cloudy with scattered light showers in the afternoon.
Wednesday
Night
Mostly cloudy with scattered light snow showers.
Wednesday
Partly to mostly sunny in the morning, becoming mostly cloudy with scattered light showers in the afternoon.
Wednesday
Night
Mostly cloudy with scattered light snow showers.
Wednesday
Partly to mostly cloudy with scattered light snow showers western part of the zone. Cloudy with light to occasionally moderate snow showers near the Cascade crest including White Pass. Periods of moderate ridgeline winds.
Wednesday
Night
Mostly cloudy with scattered light snow showers.
Wednesday
Mostly cloudy with scattered light snow showers, showers will likely increase in the afternoon. Light to moderate E Pass level and ridgeline winds.
Wednesday
Night
Cloudy with scattered light moderate snow showers. Light E Pass level and ridgeline winds.
Wednesday
Mostly cloudy with scattered light snow showers, showers will likely increase in the afternoon. Light to moderate E Pass level and ridgeline winds.
Wednesday
Night
Cloudy with scattered light snow showers. Light to moderate E Pass level and ridgeline winds.
Wednesday
Cloudy with scattered light snow showers, showers will likely increase in the afternoon. Light to moderate ridgeline winds.
Wednesday
Night
Cloudy with periods of light to occasionally moderate snow showers.
Wednesday
Cloudy with scattered light snow showers, showers will likely increase in the afternoon. Moderate ridgeline winds.
Wednesday
Night
Cloudy with periods of light to occasionally moderate snow showers.
Wednesday
Cloudy with light to occasionally moderate snow showers. Light to moderate ridgeline winds.
Wednesday
Night
Cloudy with periods of light to occasionally moderate snow showers.
Wednesday
Mostly cloudy with scattered light snow showers, showers will likely increase in the afternoon.
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).