A weak perturbation sliding down the backside of a persistent offshore ridge will bring light rain and snow to the central and northern Cascades today. The light rain and snow should increase from Mt. Baker to Snoqualmie Pass through mid-afternoon before gradually tapering through the evening hours. The ridge continues to expand into the region, moderating the temperatures as it does. Snow levels should rise from around 2500 ft Tuesday morning to 3500 ft by the end of the day and perhaps around 4000 ft by the time the rain and snow ends overnight.
Clearing skies in the wake of the perturbation will help form a shallow inversion in some areas into early Wednesday. However, the expanding ridge will raise freezing levels to above Cascade Crest level by Wednesday afternoon with mountain temperatures in the 30s and low 40s with low relative humidity. The scattered low clouds lingering along the west slopes of the Washington Cascades in the morning give way to mostly sunny skies by 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
Mostly cloudy with a slight chance of very light rain or snow.
Tuesday
Night
Partly cloudy early with mostly clearing skies overnight.
Tuesday
Cloudy with periods of increasing light rain or snow.
Tuesday
Night
Very light rain or snow decreasing or ending.
Tuesday
Light rain and snow.
Tuesday
Night
Decreasing light rain or snow ending overnight.
Tuesday
Cloudy in the northern part with a slight chance of rain or snow around Crystal Mountain. Partly cloudy skies in the southern part.
Tuesday
Night
Cloudier skies in the north with more clearing to the south.
Tuesday
Periods of light rain and snow. Light to moderate ridgeline and light W wind at the Pass.
Tuesday
Night
Light rain or snow ending during the evening hours. Light to moderate ridgeline and light W wind at the Pass.
Tuesday
Periods of light rain and snow. Moderate ridgeline and light W wind at the Pass.
Tuesday
Night
Light rain or snow ending during the evening hours. Moderate ridgeline and light W wind at the Pass.
Tuesday
Increasing light rain and snow. Slightly increasing moderate ridgeline winds.
Tuesday
Night
Mostly cloudy with a chance of flurries in the evening. Gradually decreasing 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).