A fizzling front maintains some cloud cover across the mountains of Washington State on Wednesday morning but lacks enough moisture for precipitation. A deep low tracking from SSW to NNE off the West Coast of the US will spread increasing clouds into the region from the south, leading to a mostly cloudy day. As the system approaches, easterly winds have started to increase through the mountain gaps and should continue to ramp up throughout the day. These winds will peak this evening and overnight as the deep low moves into our nearshore waters. Light to moderate snow arrives for Mt. Hood from mid-afternoon onwards with snow spreading into the Washington Cascades during the evening hours. With E winds enhancing snowfall on the east side of the mountains, models indicate the potential for significant snowfall for the east slopes south of I-90 Wednesday night. 6-12" may be possible. Temperatures should warm as SSE winds aloft gradually erode the strong cold pool east of the Cascades and more quickly warm areas west of the Cascade Crest.
Thursday will be tricky for snow levels with the cold pool weakening, E flow continuing but slightly weaker and shallower, and upper-level winds gradually shifting increasingly westerly. Snoqualmie Pass can expect to see a changeover to rain or freezing rain, but the timing remains uncertain. Precipitation amounts remain light with the highest amounts continuing along the east slopes of the Cascades and the volcanoes.
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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Wednesday
High clouds lowering and thickening.
Wednesday
Night
Increasing light rain and snow.
Wednesday
Partly to mostly sunny in the morning. High clouds lowering and thickening in the afternoon.
Wednesday
Night
Increasing light snow.
Wednesday
High clouds in the morning. Clouds lowering and thickening in the afternoon.
Wednesday
Night
Increasing light snow.
Wednesday
Mostly cloudy with high clouds lowering and thickening.
Wednesday
Night
Light rain and snow. Strong ridgeline winds near the Cascade Crest.
Wednesday
Partly cloudy in the morning, becoming mostly cloudy with a chance of very light snow developing. Moderate ridgeline and E wind at the Pass. Strong gusts likely during the afternoon.
Wednesday
Night
Increasing light snow. Moderate ridgeline and E wind at the Pass. Strong winds west of the Cascade Crest.
Wednesday
Partly cloudy in the morning, becoming mostly cloudy with a chance of very light snow developing. Moderate ridgeline and E wind at the Pass. Strong gusts likely during the afternoon.
Wednesday
Night
Increasing light snow. Moderate ridgeline and E wind at the Pass. Strong winds west of the Cascade Crest.
Wednesday
Cloudy with a chance of very light snow late in the day.
Wednesday
Night
Light snow.
Wednesday
Cloudy with very light snow developing during the afternoon.
Wednesday
Night
Increasing light snow.
Wednesday
Cloudy with very light snow developing during the afternoon.
Wednesday
Night
Moderate to heavy snow.
Wednesday
Cloudy with light snow in the afternoon, possibly becoming moderate late in the day. Moderate ridgeline winds becoming strong at times during the afternoon.
Wednesday
Night
Light to moderate rain and snow in the evening becoming light overnight. 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).