The Pacific Northwest should experience one final unseasonably warm day on Sunday as a ridge of high pressure finally begins to relax its grip on the region. Freezing levels on Sunday should be 9500-10500 ft range across the region with high temperatures mostly in the 40s with isolated areas topping 50F. Upper-level flow has shifted westerly while light E flow continues at low levels through the mountain gaps. The low-level inversion remains strong, particularly near and east of the Cascade Crest with mountain tops 21F and 13F warmer at Washington Pass and Snoqualmie Pass, respectively. Mid and high-level clouds increase across the region from late morning through the afternoon, likely obscuring skies in most areas by the end of the day. The dampening ridge axis should cross the Cascades late in the day.
Expect cloudy skies and increasing WSW winds ahead of an approaching closed low. Temperatures remain mild during the evening but should drop more drastically during the early morning hours. With increasing wind speeds and cloud cover, inversions shouldn't be as pronounced as on previous nights. Light rain and snow move into the western Olympics and Mt. Baker area during the early morning hours then spread quickly SE throughout the forecast region and the quick-moving closed low tracks into southern Washington. Mt. Baker, Paradise, and Mt. Hood can expect 3-6" of snow with 2-4" for the Cascade Passes. Snow levels around 3500 ft Monday morning should drop to 2500 ft in the afternoon. Expect strong winds developing Sunday night to peak early Monday in the Mt. Hood area, but strong gusts are also likely at Mt. Baker and in the East South Washington Cascades.
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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Sunday
Mostly sunny to start with mid-level clouds increasing from late morning onwards. Mild with a low-level inversion decreasing during the afternoon.
Sunday
Night
Clouds lowering and thickening. A chance of light rain or snow developing during the early morning hours.
Sunday
Mostly sunny to start with mid-level clouds increasing from late morning onwards. Mild with a low-level inversion decreasing during the afternoon.
Sunday
Night
Clouds lowering and thickening. Light rain or snow developing during the early morning hours.
Sunday
Mostly sunny to start with mid-level clouds increasing from late morning onwards. Mild with a low-level inversion decreasing during the afternoon.
Sunday
Night
Clouds lowering and thickening. A chance of light rain or snow developing during the early morning hours.
Sunday
Mostly sunny to start with mid-level clouds increasing during the afternoon. Mild with a low-level inversion decreasing during the afternoon.
Sunday
Night
Clouds lowering and thickening.
Sunday
Mostly sunny to start with mid-level clouds increasing during the afternoon. Mild with a low-level inversion decreasing during the afternoon. Light E winds at the Pass.
Sunday
Night
Clouds lowering and thickening. Light E winds at the Pass.
Sunday
Mostly sunny to start with mid-level clouds increasing during the afternoon. Mild with a low-level inversion decreasing during the afternoon. Light to moderate E winds at the Pass becoming light.
Sunday
Night
Clouds lowering and thickening. Light E winds at the Pass.
Sunday
Mostly sunny to start with mid-level clouds increasing during the afternoon. Mild with a low-level inversion decreasing during the afternoon.
Sunday
Night
Clouds lowering and thickening.
Sunday
Mostly sunny to start with mid-level clouds increasing during the afternoon. Mild with a low-level inversion decreasing during the afternoon.
Sunday
Night
Increasing clouds.
Sunday
Mostly sunny to start with mid-level clouds increasing during the afternoon. Mild with a low-level inversion decreasing during the afternoon.
Sunday
Night
Clouds lowering and thickening. Strong ridgeline winds gusts developing.
Sunday
Mostly sunny to start with mid-level clouds increasing during the afternoon. Mild with a low-level inversion decreasing during the afternoon.
Sunday
Night
Clouds lowering and thickening. Strong ridgeline winds developing.
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).