Tuesday will be a stormy day throughout the region as a SSW-NNE-oriented strong cold front brings plentiful moisture into the region. The front sits just offshore as of early Tuesday morning and should cross the Cascades during the early afternoon hours. Moderate to strong SW winds maintain a vast shield of heavy precipitation with a large rainshadow reducing precipitation rates for the NE Olympic mountains and perhaps slightly for Snoqualmie Pass as well. Snow levels hover between 3000-3500 ft for most of the region and have already started to decrease along the Washington Coast. The cooling and shift to W winds should come in behind the front, so expect drier snow down to Snoqualmie Pass level by the end of the day. Precipitation becomes more unstable behind the front with a slight chance of thundersnow in convergence banding that appears to set up in the northern mountain loop to just north of Washington Pass Tuesday afternoon before drifting southward during the evening hours.
Moderate to heavy snow showers continue for the central Washington Cascades through the evening hours with a strong push of W winds helping spillover into the immediate lee of the Cascade Crest. Winds and snowfall gradually decrease overnight as snow levels plummet to 1000-2000 ft.
A weak ridge offshore edges into the region as W winds decline from the moderate into the light range early Wednesday. Light snow showers taper through the morning hours with improved chances for sun breaks in the afternoon.
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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Tuesday
Light to moderate rain and snow along with cooling temperatures. Decreasing moderate ridgeline winds.
Tuesday
Night
Decreasing light to moderate snow showers.
Tuesday
Heavy rain and snow. Moderate ridgeline winds.
Tuesday
Night
Decreasing light to occasionally moderate snow showers.
Tuesday
Heavy rain and snow with heavy convergence sets up in the northern mountain loop during the afternoon. Moderate ridgeline winds with strong gusts.
Tuesday
Night
Heavy snow showers and convergence in the evening becoming light to moderate overnight.
Tuesday
Increasing heavy rain and snow at Paradise. Light rain and snow become moderate for Crystal and White Pass by mid-morning. Strong ridgeline wind gusts.
Tuesday
Night
Moderate snow showers for Paradise and White Pass with light snow showers for Crystal. Strong ridgeline wind gusts.
Tuesday
Moderate to heavy rain and snow. Snow level hovering just below the Pass. Moderate ridgeline and variable shifting W wind at the Pass.
Tuesday
Night
Moderate snow showers (heavy at times in convergence bands). Decreasing moderate ridgeline winds with strong gusts. Decreasing moderate wind at the Pass.
Tuesday
Moderate to heavy rain and snow. Snow level hovering near or just above the Pass with a cooling trend late in the day. Moderate ridgeline and variable shifting W wind at the Pass.
Tuesday
Night
Moderate snow showers (heavy at times in convergence bands). Decreasing moderate to strong ridgeline winds. Decreasing moderate wind at the Pass.
Tuesday
Increasing moderate to heavy rain and snow. Moderate winds with strong gusts.
Tuesday
Night
Decreasing light to moderate snow showers becoming light. Moderate to strong ridgelin winds in the evening decreasing overnight.
Tuesday
Increasing moderate rain and snow. Moderate to occasionally strong ridgeline winds.
Tuesday
Night
Light snow showers (moderate in convergence spillover near the Cascade Crest). Strong ridgeline winds in the evening decreasing into the moderate range.
Tuesday
Increasing rain and snow becoming moderate by mid-morning. Moderate ridgeline winds.
Tuesday
Night
Light snow showers. Moderate ridgeline winds (occasionally strong during the evening hours).
Tuesday
Cloudy to start with rain and snow by 9 AM. Rain and snow may be moderate to heavy mid-morning through the afternoon. Strong ridgeline winds.
Tuesday
Night
Moderate snow showers. Moderate to strong ridgeline winds decreasing into the moderate range.
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).