A high-pressure ridge offshore has expanded and shifted eastward, drawing much warmer air into the region this morning. This setup is creating very tricky temperature profiles in the mountains. Freezing levels won’t tell the full story, and conditions may vary substantially from one valley to the next. Despite the overall dry pattern, a few flurries can’t be ruled out near Mt. Baker or in areas favored by upslope flow in the eastern forecast zones.
Temperatures start the day quite cold in all areas near and east of the Cascade Crest. With strong overnight inversions in place, expect temperatures to warm as you ascend. Warm air continues to push north and east throughout the day, steadily raising higher-elevation temperatures. Some of the cold air near and west of the Cascades may mix out this afternoon, but below-freezing temperatures should remain entrenched in eastside valleys and passes below around 5000 ft. You'll encounter a mix of filtered sunshine and obscured skies, with an increased likelihood of obscured skies as you head north.
Monday night into Tuesday will look very similar to the past 24 hours, except temperatures continue to climb as the ridge expands further. Flurries and cloud cover should also retreat further north. By Tuesday, above-freezing temperatures rise well above our forecast elevations, reaching roughly 9,000–11,000 ft. Cold is likely to hold fast below 4000-5000 ft east of the Cascade Crest and through mountain gaps. Temperatures are likely to peak on Tuesday afternoon in many areas.
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 to mostly cloudy with mainly higher thin clouds. Warming.
Monday
Night
Monday
Mostly cloudy with snow flurries at times. Gradually warming.
Monday
Night
Partly to mostly cloudy. Gradual warming.
Monday
Partly to mostly cloudy with mainly higher thin clouds. Gradually warming.
Monday
Night
Partly cloudy with thin, high clouds. Gradually warming.
Monday
Partly cloudy with filtered sunshine. Gradually warming.
Monday
Night
Partly cloudy with thin, high clouds. Gradually warming.
Monday
Thin high clouds leading to filtered sunshine and obscured skies at times, with low clouds below 5000 ft. Temperature inversions. Light ridgeline and E wind at the Pass.
Monday
Night
Partly cloudy with thin, high clouds. Inversion and cold temperatures below 5000 ft, warm above. Light ridgeline and light to moderate E wind at the Pass.
Monday
Thin high clouds leading to filtered sunshine and obscured skies at times, with low clouds below 5000 ft. Temperature inversions. Light ridgeline and E wind at the Pass.
Monday
Night
Partly cloudy with thin, high clouds. Inversion and cold temperatures below 5000 ft, warm above. Light ridgeline and light to moderate E wind at the Pass.
Monday
Mostly cloudy with filtered sunshine. Gradually warming at upper elevations. Cold below 6000 ft.
Monday
Night
Partly cloudy with thin, high clouds. Gradually warming. Inversion and cold temperatures below 5000 ft.
Monday
Partly cloudy with filtered sunshine. Gradually warming at upper elevations. Cold below 5000 ft.
Monday
Night
Partly cloudy with thin, high clouds. Gradually warming. Inversion and cold temperatures below 5000 ft.
Monday
Partly cloudy with filtered sunshine. Gradually warming at upper elevations. Cold below 5000 ft.
Monday
Night
Mostly clear with thin, high clouds. Gradually warming. Inversion and cold temperatures below 5000 ft.
Monday
Filtered sunshine. Gradually warming.
Monday
Night
Mostly clear with thin, high clouds. Gradually warming.
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).