A well-defined low pressure slides down the coast of British Columbia on Saturday. The associated warm front lifted across the Cascades Friday night. The system continues to bring heavy snow to the Cascades early Saturday. However, warm air moving into the mid-levels through mid-day on Saturday makes the forecast tricky from Snoqualmie Pass southward. During the mid-day and early afternoon, hours expect a mix of freezing rain (west of the Cascade Crest), sleet (east of the Cascade Crest), and potentially rain in the central and southern Washington Cascades below 4500 ft. Areas that remain all snow could pick up 6-18" of snow by the end of the day with the most likely from Mt. Baker to Stevens Pass and also Paradise. Moderate to strong ridgeline winds should also peak in most areas with the cold frontal passage in the mid-afternoon hours. Areas east of the Cascade Crest may get the strongest WSW winds. Watch for heavy snowfall with a convergence zone developing in the Mountain Loop area in the late afternoon through early evening hours.
The sagging warm front focuses energy on the southern Cascades and Mt. Hood overnight. Mt. Hood could pick up 6-12" of snow with snow levels dropping to 4000 ft overnight. Washington state should cool significantly behind the Cold front as light snow showers continue across the region.
Heavy snowfall should linger over the Mt. Hood area and spills into the southern Washington Cascades as a perturbation begins to lift snowfall back northward on Sunday.
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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Saturday
Heavy rain and snow tapering late in the afternoon. Moderate to strong ridgeline winds peaking in the morning hours.
Saturday
Night
Mostly cloudy with a chance of snow flurries.
Saturday
Heavy snow decreasing slightly in the late afternoon. Moderate ridgeline winds with strong gusts.
Saturday
Night
Light snow showers.
Saturday
Heavy rain and snow with rising temperatures through early afternoon. Convergence likely late afternoon in the Mountain Loop viscinity.
Saturday
Night
Heavy snowfall possible in convergence banding during the early evening, then light snow showers.
Saturday
Heavy rain and snow at Paradise with moderate rain and snow for Crystal and White Pass. Strong sustained ridgeline winds are possible at Crystal from late morning onwards.
Saturday
Night
Moderate snow quickly tapering to light snow showers.
Saturday
Heavy snow with a slight chance of a wintry mix in the early afternoon. Light to moderate E winds at the Pass switching W and increasing in the late afternoon.
Saturday
Night
Light snow showers with a chance of convergence in the early evening. Decreasing light to moderate winds switching E at the Pass by morning.
Saturday
Heavy snow changing to a wintry mix (freezing rain west of the pass, sleet east of the Pass) during the late morning and early afternoon hours, then possibly rain below 4000 ft during the afternoon. Light to moderate E winds at the Pass switching W and increasing in the late afternoon.
Saturday
Night
Light snow showers. Decreasing light to moderate winds switching E at the Pass by morning.
Saturday
Heavy snow.
Saturday
Night
Light snow showers.
Saturday
Moderate to heavy snow with a wintry mix possible at lower elevations during the afternoon. Strong ridgeline winds.
Saturday
Night
Light snow showers.
Saturday
Moderate snow with a wintry mix changing to rain at lower elevations during the afternoon. Moderate to strong ridgeline winds.
Saturday
Night
Light snow tapering to showers.
Saturday
Moderate rain and snow. Moderate to strong ridgeline winds.
Saturday
Night
Moderate to heavy snow. 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).