A surface trough and longwave upper level trough will move through the region later this morning, bringing widespread shower activity to the Olympics and west slopes of the Cascades and lighter showers along the east slopes of the Cascades. Behind the upper trough, a change in wind direction to WNW by mid-day should allow a Puget Sound Convergence zone to form later this afternoon and last through the early morning hours of Sunday. This PSCZ should mainly be aimed in the Snoqualmie vicinity but should also impact Stevens Pass with a few additional inches of snow as well. Ridgeline westerly winds will increase in most areas late this afternoon through this evening as well. Scattered showers found elsewhere should taper off overnight. Much colder air will filter into the region and snow levels will plummet to 1000-1500' after midnight.
The calendar may say spring but a very winter-like storm will approach the area on Sunday. Light snow will overspread the mountains during the day with increasing winds and snowfall rates for the Olympics and northwest Cascades in 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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Saturday
Light to moderate rain and snow showers in the morning, becoming mostly cloudy with scattered light showers in the afternoon.
Saturday
Night
Mostly cloudy with scattered light rain and snow showers decreasing after midnight.
Saturday
Light to moderate rain and snow showers in the morning, becoming cloudy with scattered light to occasionally moderate showers in the afternoon.
Saturday
Night
Cloudy with scattered light rain and snow showers decreasing after midnight.
Saturday
Light to moderate rain and snow showers.
Saturday
Night
Light to occasionally moderate rain and snow showers becoming scattered light showers after midnight. Moderate to strong ridgeline winds.
Saturday
Light to moderate rain and snow showers in the morning, becoming mostly cloudy with scattered light showers in the afternoon. Heaviest showers Paradise area.
Saturday
Night
Cloudy with scattered light rain and snow showers decreasing after midnight.
Saturday
Light to occasionally moderate rain and snow showers in the morning, becoming cloudy with scattered light showers mid-day then increasing showers again late. Light to moderate west winds at Pass level.
Saturday
Night
Light to occasionally moderate rain and snow showers becoming scattered light showers after midnight. Moderate to strong ridgeline winds.
Saturday
Light to occasionally moderate rain and snow showers in the morning, becoming cloudy with scattered light showers mid-day then increasing showers again late. Light to moderate west winds at Pass level.
Saturday
Night
Light to moderate rain and snow showers becoming scattered light showers late. Strong ridgeline winds.
Saturday
Cloudy with scattered light rain and snow showers.
Saturday
Night
Mostly cloudy with isolated light rain and snow showers. Moderate to strong ridgeline winds.
Saturday
Cloudy with scattered light rain and snow showers. Sunbreaks further east of the Cascade crest.
Saturday
Night
Mostly cloudy with isolated light rain and snow showers. Strong ridgeline winds.
Saturday
Cloudy with scattered light rain and snow showers. Sunbreaks further east of the Cascade crest.
Saturday
Night
Mostly cloudy with isolated light rain and snow showers. Moderate to strong ridgeline winds.
Saturday
Cloudy with scattered light to occasionally moderate rain and snow showers in the morning becoming light to moderate in the afternoon.
Saturday
Night
Mostly cloudy with isolated light rain and snow showers. Strong 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).