A small-scale circulation center heads into British Columbia early Thursday morning, ushering in a cold upper trough. Brisk W winds continue to cool the atmosphere and will be impactful near and east of the Cascade Crest. The cooling air will offset much of the diurnal warming signal and change most areas to primarily snowfall. Wrap-around steadier moderate rain and snow should become showery by mid-morning. Models indicate a potential partial break in the shower activity mid-day with an organized band of precipitation moving through late in the day through the evening hours. Shower activity tapers overnight. Friday morning is the break between systems. Models have a spread in the timing of the precipitation as a trough lifts NE into southern portions of the forecast region. Expect some light snowfall to start in the southern Cascades during the afternoon.
Snow levels should fluctuate around 2000 ft on Thursday, 1000-2000 ft Thursday night, and 500-2000 ft on Friday.
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
Light snow showers.
Thursday
Night
Light snow showers in taper or end during the evening hours.
Thursday
Moderate snow early transitions to mostly light snow showers.
Thursday
Night
Light snow showers (moderate in convergence bands).
Thursday
Moderate snow becomes showery, but locally intense in convergence banding. Moderate ridgeline winds near the Cascade Crest.
Thursday
Night
Moderate snow showers and convergence banding.
Thursday
Light snow showers. Snow showers may become moderate at Paradise in the afternoon. Moderate ridgeline winds near the Cascade Crest.
Thursday
Night
Light to moderate snow showers taper overnight.
Thursday
Moderate snow and convergence in the morning becomes light snow showers in the afternoon. Moderate ridgeline and light to occasionally moderate W wind at the Pass.
Thursday
Night
Decreasing light snow showers. Decreasing light to moderate ridgeline and light W wind at the Pass.
Thursday
Moderate snow and convergence early becomes light snow showers in the afternoon. Moderate ridgeline and light to moderate W wind at the Pass.
Thursday
Night
Moderate snow showers in the evening become light overnight. Decreasing light to moderate ridgeline and light W wind at the Pass.
Thursday
Moderate snow tapers to light snow showers by mid-morning. Moderate ridgeline winds.
Thursday
Night
Light snow showers in the evening mostly end overnight. Moderate ridgeline winds become light.
Thursday
Moderate snow tapers to light snow showers early in the day. Moderate ridgeline winds.
Thursday
Night
Light snow showers in the evening mostly end overnight. Moderate ridgeline winds become light.
Thursday
Light snow showers. Moderate ridgeline winds.
Thursday
Night
Light snow showers in the evening mostly end overnight. Moderate ridgeline winds become light.
Thursday
Light to moderate snow showers. Strong ridgeline winds decrease into the moderate range.
Thursday
Night
Decreasing light snow showers. Moderate ridgeline winds become light.
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).