The remnants of a trough that has lingered off the coastline since the beginning of the weekend finally progresses through the Cascades by around 10 AM this morning. Somewhat vigorous rain and higher elevation snow shower activity continue in advance of the trough axis. The shower activity focuses on the west slopes of the Cascades and passes with some spillover just east of the Cascade Crest. However, a subtle shortwave ridge on the backside of the ridge brings a gradual end to the shower activity from 10 AM through the early evening hours. Drying occurs first in the southern Cascades before progressing northward.
The ridge axis centers over the region Tuesday evening, bringing partly cloudy skies before high clouds increase overnight ahead of a frontal system along with moderate winds focusing on the Mt Baker area.
A cold front arrives on Wednesday with the frontal passage likely in the late morning hours. Southerly winds peak early Wednesday for Mt Baker. Expect moderate precipitation for the west slopes of the Cascades (potentially heavy for Mt Baker and Paradise) before an approaching upper trough keeps light to moderate shower activity going in the afternoon. Snow levels range from 2500-4000 ft with E winds likely keeping the passes cool enough for frozen precipitation.
Weather Forecast
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West Central
West South
Stevens Pass
Snoqualmie Pass
East North
East Central
East South
Mt. Hood
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Tuesday
Mostly cloudy with a chance of light rain or snow showers, mainly during the morning hours. Sun breaks likely in the afternoon. Mostly light ridgeline winds.
Tuesday
Night
Mostly cloudy with a chance of slight chance of a light rain or snow showers. Light ridgeline winds.
Tuesday
Moderate rain or snow showers become light after 10 AM. Sun breaks at times by the afternoon. Mostly light ridgeline winds.
Tuesday
Night
Mostly cloudy with a slight chance of light rain or snow showers. Increasing moderate ridgeline winds.
Tuesday
Light to moderate rain and snow showers before 10 AM, then becoming light. Sun breaks at times by the afternoon. Light to moderate ridgeline winds.
Tuesday
Night
Mostly cloudy with a slight chance of light rain or snow showers during the evening hours with partial clearing overnight. Light ridgeline winds.
Tuesday
Light to moderate rain and snow showers before 10 AM (heaviest at Paradise), then becoming light. Plenty of sun breaks in the afternoon. Light to moderate ridgeline winds become light.
Tuesday
Night
Mostly cloudy with a slight chance of light rain or snow showers during the evening hours with partial clearing overnight. Light ridgeline winds.
Tuesday
Light to moderate rain and snow showers before 10 AM, then becoming light. Sun breaks at times by the afternoon. Mostly light ridgeline and very light E wind at the Pass becoming variable.
Tuesday
Night
Mostly cloudy with a slight chance of light rain or snow showers during the evening hours, then partial clearing overnight. Light ridgeline winds. Increasing light E wind at the Pass.
Tuesday
Light to moderate rain and snow showers before 10 AM, then becoming light. Sun breaks at times by the afternoon.
Tuesday
Night
Mostly cloudy with a slight chance of light rain or snow showers during the evening hours, then partial clearing overnight. Light ridgeline winds. Increasing light E wind at the Pass.
Tuesday
Light rain and snow showers (mainly western part) becoming mostly cloudy. Increasing mostly light ridgeline winds.
Tuesday
Night
Partly to mostly cloudy skies. Light ridgeline winds.
Tuesday
Light rain and snow showers (mainly western part) tapering, then becoming mostly cloudy. Light to moderate ridgeline winds.
Tuesday
Night
Partly to mostly cloudy skies. Light ridgeline winds.
Tuesday
Light rain and snow showers (mainly western part) tapering, then becoming mostly to partly cloudy. Decreasing mostly light ridgeline winds.
Tuesday
Night
Partly cloudy. Light ridgeline winds.
Tuesday
Light rain and snow showers quickly tapering, with plenty of sun breaks in the afternoon. Decreasing moderate ridgeline winds become light.
Tuesday
Night
A few sprinkles or flurries in the evening with partly to mostly cloudy skies. Light ridgeline winds become moderate.
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).