A cool, snowy pattern has settled into the Pacific Northwest, replacing the warm conveyor of moisture that has drifted SE into southern Oregon. With a broad upper trough over the region, expect continued mostly moderate W and WSW ridgeline winds and snow to stack up. Snow showers will be locally intense throughout the Cascades. The atmospheric instability will help some of the moisture spill over onto the east slope of the Cascades. Snow amounts on Friday should be in the 4-10" range for areas near and west of the Cascade Crest, with 1-6" amounts further east. Winds will be plenty strong to blow around the low-density snow in exposed terrain.
Snow shower activity generally increases slightly Friday night and Saturday as the upper trough digs southward offshore. Winds gradually shift toward the SW, favoring the volcanoes and Mt. Baker slightly more over time. Most locations near and west of the Cascade Crest will pick up an additional 12-20" of snow Friday night through Saturday.
Snow levels remain low throughout the short-term forecast, generally in the 1000-2500 ft range.
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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Friday
Light snow showers (moderate to heavy intensity during squalls). Increasing light to moderate ridgeline winds.
Friday
Night
Light snow showers (moderate to heavy intensity during squalls). Moderate ridgeline winds.
Friday
Increasing moderate snow showers. Increasing light to moderate 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).