The final in a series of surface lows linked to an offshore trough will transit the area today. Each low has been better developed and more moisture-laden than the previous, giving the current feature over SW Washington ample moisture to work with. The low should track NE through the central Cascades during the late morning hours. Moderate low-level E winds through the mountain gaps have been keeping much of the precipitation east of the Cascades frozen. These winds should relax somewhat as upper-level winds increase out of the WSW in the wake of the passing low. Expect increasing increasing moderate to locally heavy rain and snow for the west slopes of the Cascades today with snow changing to a wintry mix for the passes and light to moderate snow or wintry mix east of the Cascade Crest.
The trailing upper trough approaches the coast overnight with decreasing light to moderate rain and snow showers for the west slopes of the Cascades and passes. The minimal spillover to the east slopes will be a rain/snow mix as temperatures continue to warm east of the Crest.
Light rain and snow showers continue to decrease on Tuesday with the trough axis moving east during the morning area and a weak ridge bringing increasing chances for a few sun breaks in the afternoon.
Snow levels west of the Cascades will be in the 4000-5000 ft range throughout the period. East of the Cascades, snow levels rise up to around 3500-4500 ft by Tuesday.
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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Monday
Cloudy with periods of light rain and snow. Light ridgeline winds.
Monday
Night
Cloudy with decreasing periods of light rain and snow. Light ridgeline winds.
Monday
Cloudy with moderate rain and snow becoming locally heavy under convergence late in the day. Increasing light to moderate ridgeline winds.
Monday
Night
Cloudy with moderate rain and snow showers early, becoming light. Light ridgeline winds.
Monday
Cloudy with periods of moderate rain and snow. Increasing light to moderate ridgeline winds.
Monday
Night
Cloudy with moderate rain and snow showers early, becoming light. Decreasing light to moderate ridgeline winds.
Monday
Cloudy with heavy rain and snow (Paradise) and light rain and snow (White Pass). Increasing light to moderate ridgeline winds.
Monday
Night
Cloudy with periods of moderate rain and snow (Paradise) and light rain and snow (White Pass). Decreasing mostly light ridgeline winds.
Monday
Cloudy with periods of moderate rain and snow. Mostly light ridgeline and E wind at the Pass.
Monday
Night
Cloudy with periods of moderate rain and snow. Light to occasionally moderate ridgeline and variable wind at the Pass.
Monday
Cloudy with moderate rain and snow in the morning, becoming heavy at times in the afternoon. Snow should transition to rain or a wintry mix during the afternoon. Mostly light ridgeline and E wind at the Pass.
Monday
Night
Cloudy with periods of moderate rain and snow. Light to occasionally moderate ridgeline and variable wind at the Pass.
Monday
Cloudy with periods of light snow. Increasing light ridgeline winds.
Monday
Night
Cloudy with decreasing light rain or snow showers. Decreasing light to moderate ridgeline winds.
Monday
Cloudy with periods of light to moderate rain, snow, and wintry mix. Increasing moderate ridgeline winds.
Monday
Night
Cloudy with decreasing light rain or snow showers. Decreasing moderate ridgeline winds.
Monday
Cloudy with periods of light rain, snow, or freezing rain. Increasing light to moderate ridgeline winds.
Monday
Night
Cloudy with decreasing light rain or snow showers. Decreasing light to moderate ridgeline winds.
Monday
Cloudy with periods of moderate rain and snow. Increasing moderate ridgeline winds with strong gusts.
Monday
Night
Cloudy with moderate rain and snow showers. Light to 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).