An upper low dropping southward has provided support for a surface low that developed off the SW Washington Coastline Friday night. On early Saturday morning, this feature is well defined on satellite and radar imagery, spinning moisture into the region. Moderate SW winds should continue to bring moderate snowfall to the southern Washington Cascades. These winds curl around the low with a SE direction by the time they hit the Olympics, depositing heavy snow (an additional 10-15" by the evening). Moderate low-level E winds should focus light to moderate snow along the east slopes of the Cascades where we expect 1-4" of accumulation on Saturday.
A weakening offshore low drifts westward and most snowfall for the Olympics and west slopes of the Cascades becomes light to occasionally moderate Saturday night. However, a circulation center may develop a deformation band east of the Cascades that drifts northward across the central and northern Cascades bringing some moderate snowfall. Locally NE winds could focus the heaviest snow on the Mission Ridge area.
Snowfall continues in the same general area but tapers into the light range throughout the region on Sunday.
Snow levels vacillate between just above sea level in the early morning hours up to around 1500 ft each 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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Saturday
Mostly cloudy with periods of light snow. Heavy snow for SE Olympics.
Saturday
Night
Mostly cloudy with periods of light snow. Moderate snow becoming light for SE Olympics.
Saturday
Periods of light to occasionally moderate snow. Ridgeline winds increase into the moderate range.
Saturday
Night
Decreasing periods of light snow.
Saturday
Periods of light to occasionally moderate snow. Increasing moderate ridgeline winds.
Saturday
Night
Periods of light to occasionally moderate snow.
Saturday
Decreasing heavy snow at Mt. St Helen. Decreasing moderate to Heavy snow at Paradise and Mt Adams. Light to moderate snow at Crystal and White Pass.
Saturday
Night
Decreasing light to moderate snow.
Saturday
Periods of light snow may be moderate at times east of the Pass. Moderate ridgeline and light to moderate E winds at the Pass.
Saturday
Night
Periods of light snow may be moderate at times east of the Pass. Light to moderate ridgeline and light E winds at the Pass.
Saturday
Periods of light snow may be moderate at times east of the Pass. Moderate ridgeline and E winds at the Pass.
Saturday
Night
Periods of light snow may be moderate at times east of the Pass. Light to moderate ridgeline and E winds at the Pass.
Saturday
Light snow. Moderate ridgeline winds.
Saturday
Night
Light to occasionally moderate snow.
Saturday
Increasing light to moderate snow. Moderate ridgeline winds.
Saturday
Night
Moderate snow.
Saturday
Light to moderate snow.
Saturday
Night
Light to moderate snow.
Saturday
Moderate snow. Moderate ridgeline winds.
Saturday
Night
Moderate snow in the evening tapers overnight. 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).