The Pacific Northwest lies between a closed low approaching the Northern California coast and a northern branch of the jet stream that directs moisture into Northern British Columbia. The result will be mostly dry, mild weather with light winds in our region. The closed low to the south sustains high and mid-level cloud cover as far north as Snoqualmie Pass, gradually thickening into filtered sunshine/obscured skies closer to the Oregon border and for Mt Hood. Some very light drizzle could develop over Mt Hood Sunday night as the closed low moves east on Monday, resulting in the retreat of most high- and mid-level cloud cover.
Freezing levels will generally sit around 7000-8500 ft Sunday through Monday. With clearer skies, freezing levels have inverted in the typical cold, deeper valleys of the East North Cascades around Washington Pass. Expect inversions to mix out by around 10 AM and re-form Sunday night into early Monday.
Ridgeline winds will be light and variable on Sunday with light low-level E winds through mountain gaps until the early morning hours on Monday. Ridgeline winds shift WNW on Monday as a weak ridge moves into the region.
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 with a few high clouds at times. Mild.
Sunday
Night
Clear skies. Mild.
Sunday
Sunny and mild.
Sunday
Night
Clear skies. Mild.
Sunday
Mostly sunny with filtered sunshine at times in the southern part. Mild.
Sunday
Night
Clear skies. Mild.
Sunday
Filtered sunshine with mostly thin high clouds. Mild.
Sunday
Night
A few high clouds gradually clearing. Mild.
Sunday
Mostly sunny with thin, high clouds at times. Mild. Light ridgeline and E wind at the Pass.
Sunday
Night
Mostly clear. Mild. Light ridgeline winds. E winds at the pass switch to W in the early morning hours.
Sunday
Mostly sunny with thin, high clouds at times. Mild. Light ridgeline and E wind at the Pass.
Sunday
Night
Mostly clear. Mild. Light ridgeline winds. E winds at the pass switch to W in the early morning hours.
Sunday
Sunny. Mild above 5500 ft. Inversion with cold air below 5500 ft mixes out around 10 AM.
Sunday
Night
Clear skies. Inversions forming below 5500 ft.
Sunday
Sunny with a few high clouds at times. Mild.
Sunday
Night
Mostly clear skies. Mild.
Sunday
Filtered sunshine with a chance of obscured skies in the afternoon. Mild.
Sunday
Night
High clouds. Mild.
Sunday
Filtered sunshine in the morning, trending toward obscured skies in the afternoon. Mild.
Sunday
Night
Obscured skies with a slight chance of very light rain and higher elevation snow.
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).