Forecast updated 4:50 PM: Increased Snow Water Equivalent for Snoqualmie Pass on Saturday due to increased potential for convergence.
A broad trough over most of Canada and the northern United States will maintain below-normal temperatures at all elevations in our region. If you head into the mountains, bring some extra layers.
A shortwave disturbance riding down the back of the broader trough guides a surface low toward the mouth of the Columbia River, arriving around midnight. Initially isolated snow showers over the Olympics and southern Cascade Volcanoes region during the late evening hours will become scattered and expand northward overnight. Light to moderate snow shower activity peaks during the daylight hours on Saturday. Models struggle to define the probable location and strength of a convergence band developing in the central Washington Cascades Saturday afternoon. Once this band forms, it should ease southward toward the Mt Rainier area during the evening as precipitation comes to an end across the region. Expect low-density storm snow totals of 3-8” for the west slopes of the Cascades from the Mountain Loop to Mt Hood, with 1-3” elsewhere. Snow levels peak Saturday afternoon around sea level in the north and 1500 ft in the south. Ridgeline winds will be most impactful for Mt Hood where they will remain in the moderate range for much of the storm.
Some lingering clouds, flurries, and very weak convergence activity remain for the west slopes of the Cascades under NW flow aloft on Sunday. Temperatures should be comparable to Saturday but might start the colder east of the Cascades where skies are mostly clear.
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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Friday
Night
Cloudy with light snow showers developing in the early morning hours (moderate in the southern and eastern Olympics).
Saturday
Mostly cloudy with light snow showers.
Friday
Night
High clouds lower and thicken with a chance of light snow showers by morning.
Saturday
Cloudy with light snow showers.
Friday
Night
High clouds lower and thicken, with light snow showers developing in the early morning hours.
Saturday
Light snow showers, locally intense in convergence banding during the aftenroon.
Friday
Night
Isolated light snow showers in the evening, becoming scattered overnight.
Saturday
Increasing light to moderate snow showers.
Friday
Night
High clouds lower and thicken with a chance of snow flurries. Light ridgeline and W wind at the Pass switches E overnight.
Saturday
Increasing light to moderate snow showers, locally intense in convergence banding. Light ridgeline and W wind at the Pass switches E overnight.
Friday
Night
High clouds lower and thicken with a chance of snow flurries. Light ridgeline and W wind at the Pass switches E overnight.
Saturday
Increasing light to moderate snow showers, locally intense in convergence banding. Light ridgeline and W wind at the Pass switches E overnight.
Friday
Night
High clouds lower and thicken.
Saturday
Increasing light snow showers.
Friday
Night
Increasing clouds.
Saturday
Increasing light to occasionally moderate snow showers.
Friday
Night
Mostly cloudy with snow flurries near the Cascade Crest.
A dry cold front moves through the area from north to south late Monday, bringing a reinforcing shot of cold air to the region and maintaining primarily dry weather. Expect frigid temperatures Tuesday morning, particularly east of the Cascade Crest. Low-level E flow gradually increases and becomes more impactful later Monday and Tuesday.
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).