High clouds are streaming over the region this morning out ahead of a Pacific frontal system. This will be the story of the day as high clouds are thicker near the Canadian border and Olympics and more intermittent further south near Mt. Hood. The same north-to-south dynamic will exist with temperatures/freezing levels, with cooler conditions to the north and much milder conditions down near Mt. Hood. As the upper level ridge over the region flattens today, look for increasing westerly flow and ridgeline wind later this afternoon. Alpine winds will become strong especially in the Mt Hood area later today through Sunday.
The frontal system will pass through the Cascades around 5-7 am tomorrow morning. Light precipitation will develop over the north and spread south and east by daybreak Sunday. Showers will become scattered quickly behind the front. Generally, light accumulations are expected with a few inches of snow possible above 4000' from about Snoqualmie Pass and northward. Expect more clouds along the west slopes of the Cascades tomorrow and more sunshine along the east slopes in the afternoon. Winds will remain strong out of the WNW.
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
High overcast with periods of filtered sunshine.
Saturday
Night
Light rain and snow becoming scattered light showers late.
Saturday
High overcast with periods of filtered sunshine.
Saturday
Night
Cloudy with light to occasionally moderate rain and snow developing in the evening.
Saturday
High clouds with occasional filtered sunshine.
Saturday
Night
Cloudy with light rain and snow developing late evening. Increasing ridgeline winds.
Saturday
High clouds with occasional filtered sunshine.
Saturday
Night
Cloudy with light rain and snow developing after midnight. Increasing ridgeline winds.
Saturday
High clouds with occasional filtered sunshine.Light and variable winds at Pass level.
Saturday
Night
Cloudy with light rain and snow developing around midnight. Light and variable winds at Pass level.
Saturday
High clouds with occasional filtered sunshine. Light and variable winds at Pass level.
Saturday
Night
Cloudy with light rain and snow developing after midnight. Increasing ridgeline winds. Light and variable winds at Pass level.
Saturday
High clouds with occasional filtered sunshine.
Saturday
Night
Cloudy with light rain and snow developing after midnight. Increasing ridgeline winds.
Saturday
High clouds with occasional filtered sunshine.
Saturday
Night
Cloudy with light rain and snow developing late. Increasing ridgeline winds.
Saturday
High clouds with occasional filtered sunshine.
Saturday
Night
Cloudy with light rain and snow developing late. Increasing ridgeline winds.
Saturday
Partly sunny with periods of high clouds. Alpine winds becoming strong in the afternoon.
Saturday
Night
Cloudy with light rain and snow developing late. Strong 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).