Happy Winter Solstice! A frontal system will spread precipitation inland as it pushes from its current position along the coastline and crosses the Cascades in the early afternoon hours on Saturday. High snow levels well above ridgeline for most areas early this morning will quickly fall with the onset of precipitation and settle into the 4000-4500' range. Strong S-SE ridgeline winds will become blustery WSW winds with frontal passage later this afternoon. Low-level offshore flow and east winds may initially drag snow levels down to 3000' for the Cascade Passes including Snoqualmie Pass mid-day, but they should bump back up to 4000' or higher with the frontal passage.
This system will be a quick hitter, with showers becoming scattered in the evening (lingering longest in the Mt Baker area) and tapering off Saturday night. A shortwave ridge will move overhead late tonight through tomorrow morning, providing us with a brief dry period.
Another frontal system will folllow quickly on Sunday, with winds and precipitation ramping up first for the Olymipcs in the morning and then for Mt Hood and the WA Cascades in the afternoon. The Olymipcs and Mt Hood area will see the biggest warm up as warm frontal precipitation moves into the area, and to a lesser extent along the west slopes of the Cascades. The Cascade Passes and east slopes of the Cascades will stay on the cool side, at least through the daylight hours 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
Light to moderate rain and snow becoming light to occasionally moderate rain and snow showers in the afternoon. Strong winds.
Saturday
Night
Mostly cloudy with scattered light rain and snow showers in the evening. Periods of moderate ridgeline winds.
Saturday
Cloudy with light to moderate rain and snow developing late morning and becoming light to occasionally moderate rain and snow showers later in the afternoon. Strong winds.
Saturday
Night
Mostly cloudy with light to occasionally moderate rain and snow showers in the evening then tapering off after midnight. Periods of moderate ridgeline winds.
Saturday
Cloudy with light to occasionally moderate rain and snow developing late morning or mid-day, and becoming light to occasionally moderate rain and snow showers later in the afternoon. Moderate ridgeline winds.
Saturday
Night
Mostly cloudy with light rain and snow showers in the evening then tapering off after midnight. Periods of moderate ridgeline winds.
Saturday
Cloudy with light to occasionally moderate rain and snow developing late morning or mid-day, and becoming light to occasionally moderate rain and snow showers later in the afternoon. Strong ridgeline winds.
Saturday
Night
Mostly cloudy with scattered light rain and snow showers in the evening. Periods of moderate ridgeline winds.
Saturday
Cloudy with light to occasionally moderate rain and snow developing late morning or mid-day, and becoming light to moderate rain and snow showers later in the afternoon. Moderate E winds at Pass level, strong SE winds at ridgeline in the morning becoming moderate to strong WSW winds in the afternoon at both ridgeline and Pass level.
Saturday
Night
Mostly cloudy with scattered light rain and snow showers in the evening. Moderate W ridgeline and Pass level winds decreasing after midnight.
Saturday
Cloudy with light to occasionally moderate rain and snow developing late morning or mid-day, and becoming light to moderate rain and snow showers later in the afternoon. Moderate E winds at Pass level, strong SE winds at ridgeline in the morning becoming strong WSW winds in the afternoon at both ridgeline and Pass level.
Saturday
Night
Mostly cloudy with scattered light rain and snow showers in the evening. Moderate W ridgeline and Pass level winds decreasing after midnight.
Saturday
Cloudy with light to occasionally moderate rain and snow developing mid-day, and becoming light rain and snow showers later in the afternoon. Moderate to strong ridgeline winds.
Saturday
Night
Mostly cloudy with scattered light rain and snow showers in the evening. Periods of moderate ridgeline winds.
Saturday
Cloudy with light to occasionally moderate rain and snow developing late morning or mid-day, and becoming light rain and snow showers later in the afternoon. Strong ridgeline winds.
Saturday
Night
Mostly cloudy with scattered light rain and snow showers in the evening. Periods of moderate ridgeline winds.
Saturday
Cloudy with light to occasionally moderate rain and snow developing late morning or mid-day, and becoming light rain and snow showers later in the afternoon. Strong ridgeline winds.
Saturday
Night
Mostly cloudy with scattered light rain and snow showers in the evening. Periods of moderate ridgeline winds.
Saturday
Cloudy with light to moderate rain and snow developing late morning, and becoming light to moderate rain and snow showers later in the afternoon.
Saturday
Night
Mostly cloudy with scattered light rain and snow showers in the evening. Periods of 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).