The upper low that has been off the west coast for several days reached the California coastal waters on Wednesday morning. A final wave of associated moisture dissipates over southern Washington this morning and might bring a passing snow flurry to some areas. Clear skies and light winds in the northern Washington Cascades allowed temperatures to cool significantly overnight. The 6 AM temperature at the Washington Pass lower station sits at a crisp 5 F. A mostly sunny morning in over these same areas with clear skies should allow temperatures to rebound rapidly through the morning hours. The weak tail end of a shortwave trough moving across Canada will enhance the chances for some light snow across the North Cascades late Wednesday afternoon into the early evening hours. Elsewhere, expect another day of convective cloud build-up and scattered convective snow and graupel showers. We expect an inch or less of snow accumulation in all areas. While temperatures may rise above freezing up to 4000 ft during periods of sunshine today, expect precipitation to lower snow levels down to the 2500-3000 ft range.
A ridge of high-pressure wedges into the region, bringing an end to lingering snow showers in the early evening. Skies should clear and temperatures will plummet overnight.
After another chilly start to the day on Thursday with inversions in valley locations, expect milder temperatures with freezing levels in the 4000-5000 ft range by the afternoon. Winds remain unusually light.
Weather Forecast
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West South
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East Central
East South
Mt. Hood
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Wednesday
Mostly clear early, then becoming mostly cloudy by late morning with a chance of light snow showers.
Wednesday
Night
Clearing skies.
Wednesday
Mostly clear early, then becoming mostly cloudy by afternoon with a chance of light snow showers.
Wednesday
Night
A chance of very light snow in the early evening, then clearing skies.
Wednesday
Mostly clear in the morning, then becoming partly cloudy in the afternoon with a chance of isolated snow showers. Variable winds at the Pass.
Wednesday
Night
Clearing skies. Light W winds switching E at the Pass.
Wednesday
Mostly clear in the morning, then becoming partly cloudy in the afternoon with a chance of isolated snow showers. Variable winds at the Pass.
Wednesday
Night
Snow flurries possible in the evening, then clearing skies. Light W winds switching E at the Pass.
Wednesday
Mostly clear in the morning, then increasing clouds in the afternoon with a chance of isolated snow showers.
Wednesday
Night
Clearing skies.
Wednesday
Mostly clear in the morning, then increasing clouds in the afternoon with a chance of isolated snow showers.
Wednesday
Night
Clearing skies.
Wednesday
Mostly clear in the morning, then increasing clouds in the afternoon with a chance of isolated snow showers.
Wednesday
Night
Clearing skies.
Wednesday
More sun than clouds. A slight chance of isolated snow showers in the afternoon.
Wednesday
Night
Clearing skies.
Wednesday
Partly cloudy with thickening clouds in the afternoon and isolated snow showers.
Wednesday
Night
Snow flurries possible in the evening, then clearing skies.
Wednesday
Partly cloudy in the morning, then becoming mostly cloudy with increasing chances of isolated snow showers.
Wednesday
Night
Snow flurries possible in the evening, then clearing skies.
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).