Weak warm frontal moisture will ride up and over an upper level ridge parked off our coast today through Thursday bringing light to moderate snowfall to our mountains, a slow but steady warming trend and increasing W-NW ridgeline winds. Weak echoes are already apparent on radar over the area this morning and light snowfall should develop for most areas later this morning through mid-day, increasing to steadier light snow in the afternoon. More moderate snowfall is likely Wednesday night near and west of the Cascade crest with lighter amounts along the east slopes of the Cascades, Olympics and Mt Hood. Through Thursday afternoon, storm totals of 4-12 inches along the west slopes of the Cascades and Passes are likely with lighter amounts elsewhere.
Snow levels will creep up slowly over the next 36 hours with the rain line working its way up the mountain more quickly over the Olympics and more gradually over the Cascades. The precipitation now looks to hang out through much of Thursday without much of a drying or clearing trend expected. WNW ridgeline winds will become moderate to locally strong this afternoon through Thursday morning with even stronger winds developing in alpine areas.
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
Light snow developing this morning and increasing in the afternoon.
Wednesday
Night
Light rain and snow.
Wednesday
Light snow developing this morning and increasing in the afternoon.
Wednesday
Night
Light to occasionally moderate snow.
Wednesday
Light snow developing this morning and increasing in the afternoon.
Wednesday
Night
Light to occasionally moderate snow.
Wednesday
Light snow developing later this morning and increasing in the afternoon.
Wednesday
Night
Light to occasionally moderate snow.
Wednesday
Light snow developing this morning and increasing in the afternoon. Light east winds in the Passes, moderate NW winds at ridgeline.
Wednesday
Night
Light to occasionally moderate snow. Moderate westerly pass level and ridgeline winds.
Wednesday
Light snow developing later this morning and increasing in the afternoon. Light east winds in the Passes, moderate NW winds at ridgeline.
Wednesday
Night
Light to moderate snow. Moderate westerly pass level and ridgeline winds.
Wednesday
Light snow developing near the Cascade crest this morning and increasing in the afternoon.
Wednesday
Night
Light snow, heaviest near the Cascade crest.
Wednesday
Light snow developing near the Cascade crest later this morning and increasing in the afternoon.
Wednesday
Night
Light snow, heaviest near the Cascade crest. Strong ridgeline winds.
Wednesday
Light snow developing near the Cascade crest later this morning or midday and increasing in the afternoon.
Wednesday
Night
Light snow, heaviest near the Cascade crest. Strong ridgeline winds.
Wednesday
Light snow developing later this morning or midday and increasing in the afternoon. Strong ridgeline winds developing this afternoon.
Wednesday
Night
Light to occasionally moderate snow. 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).