A cold trough sits over the Pacific Northwest with waves of shower activity arriving on NW flow aloft. Shower activity spans the length of the Cascades early Thursday. The first wave moves through early Thursday with light to moderate snow showers for the Washington Cascades and heavy snow for Mt Hood. The second reinforcing wave arrives in the mid-day hours and primarily impacts Highway 2 southward with the heaviest snow showers for Mt Rainier and particularly Mt Hood. W or WNW ridgeline winds will be moderate to occasionally strong for the central Washington Cascades southward, with strong winds and extreme gusts for Mt Hood. A modified arctic front dropping southward from the Canadian border during the afternoon will lower temperatures toward the end of the day. It will also cut off precipitation and enable Fraser outflow winds to bring cold air from interior British Columbia into western Watcom County.
The secondary disturbance focus on Mt Hood with the heaviest snowfall and winds peaking during the evening hours and decreasing slightly overnight. For Washington, light snow showers and light to moderate ridgeline winds ease as by far the coldest air of the year settles into the area. Expect temperatures to drop below zero in many areas.
Sunday will be partly cloudy to mostly clear for northern Washington while decreasing moderate snow continues for Mt Hood. Southern Washington will be transitional with decreasing light snow flurries and some sun breaks. Temperatures will be bitterly cold to start with daytime warming only into the 10s in many areas. Bundle up!
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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Thursday
Increasing chances of light snow showers. Cold with temperatures dropping during the day.
Moderate snow showers increase in the afternoon. Cold with temperatures dropping during the afternoon hours. Moderate to strong ridgeline winds.
Thursday
Night
Decreasing light snow showers. Moderate ridgeline winds become light to moderate. Bitterly cold.
Thursday
Decreasing light snow showers. Cold with temperatures dropping during the day. Decreasing moderate ridgeline winds. Decreasing light to occasionally moderate W wind at the Pass.
Thursday
Night
Decreasing light snow showers. Decreasing light to moderate winds. Light W wind switching E at the Pass. Bitterly cold.
Thursday
Decreasing light to moderate snow showers. Cold with temperatures dropping during the day. Moderate to strong ridgeline winds. Decreasing moderate W wind at the Pass.
Thursday
Night
Decreasing light snow showers. Decreasing light to moderate winds. Light W wind switching E at the Pass. Bitterly cold.
Thursday
Decreasing light snow showers. Cold with temperatures rapidly dropping in the afternoon.
Thursday
Night
Snow flurries in the evening ending with partially clearing skies. Bitterly cold.
Thursday
Light to occasionally moderate snow showers. Moderate to strong ridgeline winds. Cold with temperatures dropping during the day.
Thursday
Night
Decreasing light snow showers. Bitterly cold.
Thursday
Increasing light snow showers may become moderate in the afternoon.
Thursday
Night
Decreasing light snow showers. Very cold.
Thursday
Heavy snow early, then heavy snow showers. Increasing strong winds with extreme gusts.
Thursday
Night
Very heavy snow. Strong to extreme ridgeline winds decreasing overnight.
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).