Forecast updated 7:30 AM to reflect more cloud cover than originally forecast.
An expanding ridge of high pressure brings another beautiful spring day in the mountains. Temperatures start above freezing in many locations with the exception of locations where cooler temperatures have settled into valley locations. These shallow inversions should generally mix out by 10 AM. April Fools day features warm temperatures with freezing levels rising to 7500-11000 ft. Mid-level cloud cover will be more extensive over northern Washington as clouds round the top of the ridge while skies will be sunnier further south. WNW flow aloft will bring moderate ridgeline winds to the mountain gaps, areas east of the Cascade Crest and Mt Hood.
Monday night, the ridge axis shifts over the area. This will keep us dry and warm, with inversions forming once again in valley locations. Expect a poor overnight refreeze in many areas, particularly as high clouds become slightly more extensive over NW Washington.
On Tuesday, the ridge axis shifts east as a frontal system approaches from the northwest. Freezing levels gradually lower and mid-level cloud cover increases, particularly for the northern half of Washington State. Although the freezing levels lower slightly, most locations will experience warmer temperatures than Monday, particularly east of the Cascade Crest. Light precipitation could reach the western Olympic Mountains by the end of the day.
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
Partly cloudy.
Monday
Night
Mostly clear. Modest temperature inversions are possible in the mountain valleys.
Monday
Mostly cloudy.
Monday
Night
Mostly clear. Modest temperature inversions are possible in the mountain valleys.
Monday
Partly cloudy.
Monday
Night
Mostly clear. Modest temperature inversions are possible in the mountain valleys.
Monday
Partly cloudy.
Monday
Night
Mostly clear. Modest temperature inversions are possible in the mountain valleys.
Monday
Partly cloudy. Light ridgeline and increasing light W wind at the Pass.
Monday
Night
Mostly clear with a few high clouds. Modest temperature inversions are possible. Light ridgeline and light W wind at the Pass.
Monday
Partly cloudy. Moderate ridgeline and increasing light W wind at the Pass.
Monday
Night
Mostly clear with a few high clouds. Modest temperature inversions are possible. Decreasing light to moderate ridgeline and light W wind at the Pass.
Monday
Partly cloudy. Inversion mixing out by 10 AM.
Monday
Night
Mostly clear with a few high clouds. Modest temperature inversions.
Monday
Mostly sunny with a few passing high clouds. Moderate ridgeline winds.
Monday
Night
Mostly clear with a few high clouds. Modest temperature inversions.
Monday
Mostly sunny with a few passing high clouds.
Monday
Night
Mostly clear with a few high clouds. Modest temperature inversions.
Monday
Mostly sunny with a few passing high clouds. Moderate ridgeline winds with strong gusts.
Monday
Night
Mostly clear with a few high clouds. Moderate ridgeline winds at times.
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).