A closed low off the Alaska panhandle is attached to a wet and juicy system that is moving over the Pacific Northwest on Monday morning. A warm front is lifting over the area during the morning hours bringing mild temperatures to the west of the Cascade Crest where snow levels have reached 4000-5000 ft in many locations. With the front and trough offshore, moderate E flow should keep the passes cooler, although erosion of the cold air pool will continue and Snoqualmie may mix with rain in the late morning hours before W winds come in behind the cold front and bump up snow levels in the passes to above Snoqualmie Pass level. Expect post-frontal showers in the afternoon with WSW flow continuing to moderate rain and snow. Snow levels will be lowering and should get down to 3000 ft by the late evening hours. High-resolution models indicate convergence activity focusing on the Mt. Baker and Mountain loop areas in the afternoon, then shifting southward towards Stevens and Snoqualmie Passes during the evening hours. The convergence could reach Snoqualmie just around the time temperatures are cool enough for snow once again. Snow shower activity gradually eases later Monday night as temperatures continue to drop.
Expect mostly cloudy skies with some light snow showers on Tuesday morning, but with sun breaks possible. Increasing light to moderate snow is likely to develop later in the day, with southerly winds focusing the precipitation on the Olympics and Mt. Baker as a strong front approaches from the west.
Weather Forecast
Olympics
West North
West Central
West South
Stevens Pass
Snoqualmie Pass
East North
East Central
East South
Mt. Hood
Use dropdown to select your zone
Monday
Moderate rain and snow becoming light showers by mid-morning.
Monday
Night
Mostly cloudy with a chance of light snow showers.
Monday
Heavy rain and snow becoming moderate by mid-afternoon.
Monday
Night
Moderate snow showers in the evening becoming light.
Monday
Heavy rain and snow becoming moderate by mid-afternoon, but locally heavy in convergence bands.
Monday
Night
Moderate snow showers and well-defined convergence, becoming light overnight.
Monday
Heavy rain and snow in the morning becoming light to moderate showers in the afternoon.
Monday
Night
Moderate snow showers becoming light overnight.
Monday
Heavy rain and snow in the morning becoming light to moderate showers in the afternoon. Light E winds at pass level switching west in the afternoon.
Monday
Night
Moderate snow showers and well-defined convergence, becoming light overnight.
Monday
Heavy rain and snow in the morning becoming light to moderate showers in the afternoon. At pass level, snow likely until 10 AM, then mixing with rain until noon, then rain showers in the afternoon. Light to moderate E winds at pass level switching west in the afternoon.
Monday
Night
Moderate snow showers and well-defined convergence, becoming light overnight.
Monday
Moderate snow in the morning, then decreasing and mixing with rain at lower elevations in the afternoon.
Monday
Night
Light snow showers heaviest near the Cascade Crest and tapering off overnight.
Monday
Moderate rain and snow in the morning, then decreasing and becoming showery in the afternoon.
Monday
Night
Light rain and snow showers heaviest near the Cascade Crest and tapering off overnight.
Monday
Moderate rain and snow in the morning, then decreasing and becoming showery in the afternoon.
Monday
Night
Light rain and snow showers heaviest near the Cascade Crest and tapering off overnight.
Monday
Moderate to occasionally heavy rain and snow in the morning, then decreasing and becoming showery in the afternoon.
Monday
Night
Moderate snow showers becoming light and decreasing after midnight.
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).