The ridge of high pressure that brought us a nice, dry and mostly sunny weekend has begun to weaken and retrograde further offshore this morning. High clouds streaming over the top of the ridge will continue to filter in today, resulting in partly sunny skies and periods of filtered sunshine. A front will swing southward from the Canadian prairies over the next 24 hours and help dig a cool upper level trough over the Pacific Northwest. The result will be increasing low clouds this afternoon along the west slopes of the Cascades from the Canadian border to roughly Snoqualmie Pass, and then light snow beginning for the same areas later this evening. Moderate to strong NW ridgeline winds will continue for most areas through Monday night.
As the upper level trough digs offshore tonight and Tuesday, precipitation will spread southward. Light snow above 2500-3500' will produce several inches across the region through Wednesday morning, with the highest amounts for the south/central Washington Cascades and Mt. Hood. A drying trend will limit snowfall accumulations for the north Cascades and colder as drier air infiltrates from the Canadian interior behind the front.
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 sunny with periods of filtered sunshine and high clouds.
Monday
Night
Cloudy with light rain and snow developing overnight.
Monday
Partly sunny with periods of filtered sunshine and high clouds this morning, then becoming cloudy in the afternoon.
Monday
Night
Cloudy with light rain and snow developing in the evening.
Monday
Partly sunny with periods of filtered sunshine and high clouds this morning, then becoming cloudy in the afternoon. Moderate ridgeline winds.
Monday
Night
Cloudy with light rain and snow developing in the evening.
Monday
Partly sunny with periods of filtered sunshine and high clouds. Moderate ridgeline winds.
Monday
Night
Becoming cloudy with light rain and snow developing after midnight. Moderate ridgeline winds.
Monday
Partly sunny with periods of filtered sunshine and high clouds this morning, then becoming cloudy in the afternoon. Moderate ridgeline winds. Light west winds at Pass level.
Monday
Night
Cloudy with light rain and snow developing late in the evening. Moderate ridgeline winds. Light west winds at Pass level.
Monday
Partly sunny with periods of filtered sunshine and high clouds this morning, then becoming cloudy in the afternoon. Moderate to strong ridgeline winds. Light to moderate west winds at Pass level.
Monday
Night
Cloudy with light rain and snow developing late in the evening. Moderate to strong ridgeline winds. Light to moderate west winds at Pass level.
Monday
Partly sunny with periods of filtered sunshine and high clouds. Moderate ridgeline winds.
Monday
Night
Becoming cloudy with light rain and snow developing after midnight.
Monday
Partly sunny with periods of filtered sunshine and high clouds. Moderate to strong ridgeline winds.
Monday
Night
Becoming cloudy with light rain and snow developing after midnight. Moderate to strong ridgeline winds.
Monday
Partly sunny with periods of filtered sunshine and high clouds. Moderate to strong ridgeline winds.
Monday
Night
Becoming cloudy with light rain and snow developing after midnight. Moderate ridgeline winds.
Monday
Partly sunny with periods of filtered sunshine and high clouds. Moderate to strong ridgeline winds.
Monday
Night
Partly cloudy then becoming cloudy late. Moderate to strong ridgeline winds.
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).