A cold upper low continues to rotate off the Pacific Northwest coastline, driving mostly light low-level E flow through the mountain gaps. The low continues to usher light to moderate Fraser outflow winds into western Watcom County through the short-term forecast. Generally, light snow shower activity focuses on the Olympics and the northern half of the Washington Cascades early Wednesday. The upper-level steering winds around the low should guide the shower activity northward, decreasing shower activity over the Cascades and increasing the chances of sunshine as the day progresses. Satellite imagery shows additional snow shower activity offshore that will continue to rotate into the Olympics through the afternoon.
The center of cold upper low retrogrades westward Tuesday evening, further decreasing shower activity. A surface feature associated with the upper low likely pivots toward the mouth of the Columbia River overnight, resulting in some increased light snow shower activity for Mt Hood and SW Washington. Expect light to moderate snow showers for the southern half of the Washington Cascades with more isolated snow shower activity further north. Mt Hood can expect 3-6" with this feature, while areas further north can expect 1-4" of snow.
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
Isolated light snow showers in the morning. Periods of steadier light snow in the afternoon.
Tuesday
Night
Decreasing chances of light snow or snow showers.
Tuesday
Light snow showers, primarily in the morning hours, then some sun breaks in the afternoon.
Tuesday
Night
Mostly clear in the evening, then becoming mostly cloudy in the early morning hours.
Tuesday
Light snow showers, primarily in the morning hours, then some sun breaks in the afternoon.
Tuesday
Night
Partly cloudy with clouds increasing in the early morning hours.
Tuesday
Mostly cloudy in the morning with decreasing chances of an isolated snow shower or flurry.
Tuesday
Night
Increasing chances of isolated light snow showers.
Tuesday
A chance of isolated snow showers in the morning, then becoming mostly cloudy. Light ridgeline and E wind at the Pass.
Tuesday
Night
Mostly cloudy with some snow flurries. Light ridgeline and E wind at the Pass.
Tuesday
A chance of isolated snow showers in the morning, then becoming mostly cloudy. Light ridgeline and E wind at the Pass.
Tuesday
Night
Mostly cloudy with some snow flurries. Light ridgeline and E wind at the Pass.
Tuesday
A chance of isolated snow showers in the morning, then becoming mostly cloudy.
Tuesday
Night
Mostly cloudy with some snow flurries.
Tuesday
A chance of isolated snow showers in the morning, then becoming mostly cloudy.
Tuesday
Night
Mostly cloudy with some snow flurries.
Tuesday
Mostly cloudy in the morning, then becoming partly cloudy in the afternoon.
Tuesday
Night
Isolated light snow showers.
Tuesday
Mostly cloudy with isolated snow showers and flurries. Light to occasionally moderate ridgeline winds.
Tuesday
Night
Isolated light snow showers become scattered overnight. Increasing light to 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).