The atmospheric river that won't quit continues to bring heavy rain and the highest-elevation snow over the central Washington Cascades. The atmospheric stability conditions are such that the brisk winds bringing moisture over the Olympics mostly split the rain and form a wide zone of convergence in the lee of the range. This convergence targets the southern Mountain Loop to Mt Rainier with the very heavy swath precipitation extending significantly onto the east slopes of the Cascades. The southward shift of the precipitation has brought significant cooling to the northern half of Washington State, with snow levels dropping to 3500-5500 ft from Snoqualmie Pass northward. Areas on the southern side of the convergence won't experience much cooling (Mt Rainier southward). Precipitation decreases significantly after 10 AM in most areas, except in the southern Cascade Volcanoes (including Mt. Hood).
The remnants of the stalled front continue to bring clouds, warm air, and more modest amounts of moisture into the region Thursday night and Friday. Most areas will experience periods of light rain and higher elevation snow throughout this period, along with a warming trend. Areas north of Hwy 2 could pick up an inch or so of snow before precipitation changes back to rain, with Washington Pass staying all snow.
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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Thursday
Periods of light rain and snow. Light to moderate ridgeline winds.
Thursday
Night
Periods of light rain and higher elevation snow.
Thursday
Cloudy with periods of light rain or snow in the afternoon.
Thursday
Night
Periods of light rain and higher elevation snow.
Thursday
Heavy rain and snow in the southern part. Cloudy with periods of light rain or snow in the afternoon further north.
Thursday
Night
Periods of light rain and higher elevation snow.
Thursday
Heavy rain and snow becomes light to moderate by the afternoon. Moderate ridgeline winds, strong gusts.
Thursday
Night
Decreasing moderate rain and highest elevation snow at Paradise (light elsewhere). Light to moderate ridgeline winds.
Thursday
Heavy rain and snow become mostly light by the afternoon. Moderate ridgeline and light to moderate W wind at the Pass.
Thursday
Night
Periods of light rain and highest elevation snow. Light to moderate ridgeline and light W wind at the Pass.
Thursday
Heavy rain and snow become mostly light by the afternoon. Moderate ridgeline and W wind at the Pass.
Thursday
Night
Periods of light rain and highest elevation snow. Moderate ridgeline and light to moderate W wind at the Pass.
Thursday
Periods of light rain and snow. Decreasing moderate ridgeline winds.
Thursday
Night
Periods of light rain and snow.
Thursday
Moderate rain and higher elevation snow become light. Moderate ridgeline winds, strong gusts.
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).