An upper-level and surface low center west of the Columbia River mouth continues to pull cold air from the interior through the mountain gaps and into western Washington and Oregon. Small amounts of moisture wrapping around the low continue to bring periods of light snow to parts of western Washington and Oregon (including the lowlands!) with unusually high snow-to-water ratios. The SE slopes of the Olympics stand to pick up the most snow (perhaps 2-6") while Mt. Hood could also pick up a trace to 2" of snow. Most other areas should experience decreasing snow flurry activity as the offshore low drifts southward. Expect increasing chances for partially clearing skies from north to south throughout the day. Mountain temperatures started the day on Thursday in the negative single digits and single digits in most areas. Temperatures will struggle to get out of the single digits and low 10s by the afternoon. Moderate ESE winds near the Cascade Crest may be locally strong and should gradually decrease for the mountains of Washington State. Light to moderate winds near Mt. Hood may peak during the evening hours before decreasing overnight. Across the region, prepare for dangerously cold wind chills.
By Thursday night, the offshore low should be off the N California coastline, leaving light (or no) wind aloft over our region. Expect very cold temperatures Thursday night with more negative and single-digit temperatures. Valley locations may be the coldest E winds continue to decrease.
Friday remains bitterly cold with similar temperatures to Thursday. NNW flow aloft develops by Friday afternoon with sunny skies giving way to a few high clouds across NW Washington by the afternoon.
Updated 10:18 AM to include missing freezing/snow levels.
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
Bitterly cold. Periods of light snow or flurries decreasing. Sun breaks more likely in the afternoon.
Thursday
Night
Bitterly cold and mostly clear with a few low clouds banked against the north slope of the range.
Thursday
Bitterly cold. Partly cloudy with a few snow flurries in the morning, becoming mostly sunny late in the day.
Thursday
Night
Bitterly cold. Mostly clear.
Thursday
Bitterly cold. Partly cloudy with a few snow flurries in the morning, becoming mostly sunny late in the day.
Thursday
Night
Bitterly cold. Mostly clear.
Thursday
Bitterly cold. Mostly cloudy with a few snow flurries in the morning, becoming partly sunny by the afternoon.
Thursday
Night
Bitterly cold. Clear skies.
Thursday
Bitterly cold. Partly cloudy with a few snow flurries in the morning, becoming mostly sunny late in the day. Moderate ridgeline and E winds at the Pass decreasing into the light range.
Thursday
Night
Thursday
Bitterly cold. Partly cloudy with a few snow flurries in the morning, becoming mostly sunny late in the day. Moderate ridgeline and E winds at the Pass.
Thursday
Night
Bitterly cold. Clear skies. Decreasing light to occasionally moderate ridgeline and E wind at the Pass.
Thursday
Bitterly cold. Partly cloudy with snow flurries.
Thursday
Night
Bitterly cold. Clear skies.
Thursday
Bitterly cold. Mostly cloudy with a chance of snow flurries.
Thursday
Night
Bitterly cold. Clear skies.
Thursday
Bitterly cold. Mostly cloudy with a chance of snow flurries.
Thursday
Night
Bitterly cold. Mostly clear skies.
Thursday
Mostly cloudy with snow flurries or periods of light snowfall. Becoming partly cloudy late in the day.
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).