A strong frontal system starts cold and snowy, but finishes warm and wet, with the devil in the details.
Light snow begins in the Olympic mountains early Saturday morning, gradually extending to the western and then eastern slopes of the Cascades around late morning and mid-day, respectively. Dry lower levels of the atmosphere could delay the onset of precipitation by an hour or two as precipitation may originally evaporate as it falls. Most major trailheads should see snowfall continuing through the day. While most areas have snow levels around 1500-2000 ft, a warming trend begins to impact the Olympics and Mt Hood late where snow levels may rise to 3000-4000 ft by the end of the day.
Snowfall intensity and SW through SE winds are anticipated to intensify in the afternoon, leading to 3-10" of snow by the evening in most areas. Precipitation and moderate winds peak Saturday night into Sunday morning as the moisture stream directly targets the area and the cold front arrives from the NW. Snow levels rise sharply from the evening through the overnight hours. However, a cool easterly flow and the presence of low-level cold air on the eastern slopes of the Cascades will maintain snow or frozen precipitation longer through the mountain gaps. The Passes and lower elevations along the East slopes of the Cascades might experience freezing rain during this period, but significant icing is not anticipated. Models continue to indicate that the central and southern Washington Cascades, along with Mt. Hood, will receive the most precipitation over the weekend, however, Mt Baker looks wetter than originally forecast at the start of the storm. The heavier precipitation is expected to gradually diminish from north to south on Sunday as the moisture feed shifts southward into Oregon.
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 snow develops by mid-morning and becomes moderate to heavy by the afternoon.
Saturday
Night
Decreasing light to moderate rain and snow becomes showery. Rapidly rising snow levels.
Saturday
Cloudy in the morning with increasing snow developing late morning and becoming heavy late in the day.
Saturday
Night
Moderate to heavy snow becomes showery in the early morning hours. Rapidly rising snow levels.
Saturday
Cloudy with moderate to heavy snow from late morning onwards.
Saturday
Night
Heavy rain and snow. Rapidly rising snow levels.
Saturday
Cloudy early, then moderate to heavy snow from mid-morning onwards.
Saturday
Night
Heavy rain and snow. Rapidly rising snow levels.
Saturday
Cloudy early, then moderate to heavy snow develops. Moderate ridgeline and light to moderate E winds at the Pass.
Saturday
Night
Heavy snow in the evening, with freezing rain or rain at times after midnight. Moderate ridgeline and light to moderate E winds at the Pass.
Saturday
Cloudy early, then moderate to heavy snow develops. Moderate ridgeline and light to moderate E winds at the Pass.
Saturday
Night
Heavy snow in the evening, with freezing rain or rain at times from late evening onwards. Moderate ridgeline and light to moderate E winds at the Pass.
Saturday
Cloudy with light to moderate snow developing in the afternoon.
Saturday
Night
Moderate snow in the evening becoming light and more showery overnight.
Saturday
Cloudy with light to moderate snow developing late morning.
Saturday
Night
Moderate to heavy snow mixing with freezing rain or rain in the early morning hours.
Saturday
Cloudy with light to moderate snow developing late morning.
Saturday
Night
Moderate to heavy snow mixing with or changing to freezing rain or rain after midnight
Saturday
Cloudy in the morning with moderate snow developing from mid-morning onwards. Moderate ridgeline winds become strong.
Saturday
Night
Heavy snow changes to heavy rain by late evening. 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).