A plume of moisture is rounding over a broad offshore ridge into our area on strong NW flow aloft. A disturbance arriving today has started to spread light snowfall into the area which should increase into the moderate range from Snoqualmie Pass to Mt. Baker where 4-8" of snow are possible by the end of the day. Crystal Mountain appears to be partially blocked by Mt. Rainier due to the westerly low-level flow. Winds are ramping up into the moderate range at many NWAC stations Thursday morning, particularly in the southern Washington Cascades, Mt. Hood area, the Cascade Passes, and along the east slopes of the Cascades. The White Pass upper station already has strong (30+ mph) winds.
A stronger impulse of energy arrives tonight as snow increases into the moderate to heavy range from Paradise to Mt. Baker. Another 6-12" of snow are likely above 3500 ft. Lower elevations such as Snoqualmie Pass should see snow totals significantly diminished by a rain/snow mix. Mt. Hood should start to get some light snowfall as well. Westerly winds will ramp up into the moderate to strong range after midnight into early Friday. The strongest winds will be along the east slopes of the Cascades and Mt. Hood where very strong to extreme gusts are likely.
On Friday, the pulse of energy shifts east of our region allowing snowfall to decrease from the moderate to the light range. Snow levels begin to drop toward the end of the day.
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
Increasing light snow.
Thursday
Night
Light snow. Moderate ridgeline winds may be strong at times after midnight.
Thursday
Light snow early, then moderate snow.
Thursday
Night
Heavy rain and snow. Moderate ridgeline winds with strong gusts.
Thursday
Light snow early, then moderate snow.
Thursday
Night
Heavy rain and snow. Moderate ridgeline winds with strong gusts.
Thursday
Increasing light snow, heaviest at Paradise.
Thursday
Night
Heavy snow at Paradise and White Pass with light to moderate snow at Crystal. Increasing moderate to occasionally strong ridgeline winds.
Thursday
Moderate snow developing. Light W wind at the Pass.
Thursday
Night
Heavy rain and snow. Light to moderate W wind at the Pass.
Thursday
Light snow early, becoming moderate. W wind increasing into the light to moderate range at the Pass. Strong ridgeline wind gusts likely late in the day.
Thursday
Night
Heavy rain and snow. Snow levels near or slightly above the Pass. Increasing moderate W winds at the Pass. Moderate to occasionally strong ridgeline winds.
Thursday
Increasing light snow.
Thursday
Night
Moderate snow. Increasing moderate to occasionally strong ridgeline winds.
Thursday
Increasing light snow.
Thursday
Night
Moderate snow. Strong ridgeline winds, likely very strong in the Wenatchee Mountains.
Thursday
Increasing light snow becoming a mix of rain and snow in the afternoon with rising snow levels.
Thursday
Night
Light snow. Increasing moderate to strong ridgeline winds.
Thursday
Cloudy with very light snow possible at times. Increasing moderate to strong ridgeline winds.
Thursday
Night
Increasing light snow. Increasing strong ridgeline winds with very strong to extreme gusts.
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).