Expect stormy weather with occasionally heavy snowfall and strong and gusty winds for much of the Cascades Friday from the Mt Loop area south to Mt Hood. Several bands of precipitation stretch into the mountains this morning driven by a short-wave weather system moving across the Pacific Northwest. This pattern should continue through the day and into the evening. Puget Sound Convergence Zones forming off the Olympics and Vancouver Islands will focus narrow swaths of heavier precipitation into the Central Cascades. Look for these bands to pass briefly over and near both Hwy 2 and I90 Friday morning and again in the evening. The bulk of the moisture with this shortwave system will take aim at Mt Hood and the southern Washington volcanoes during the day. In these locations look for moderate to occasionally heavy snow. Strong northwesterly winds will continue to impact the mountains on both sides of the Cascades through the day and into the evening.
Drier northerly flow should quickly bring an end to the precipitation early Saturday morning. The question will be, will we dry out enough to see significant sunshine? Areas east of the Cascade Crest may find partly to mostly sunny skies. For other locations, low-level moisture should keep clouds in the mountains at least through the morning, but you may experience longer periods of blue sky 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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Friday
Cloudy with isolated snow showers.
Friday
Night
Cloudy with isolated snow showers.
Friday
Cloudy with scattered snow showers.
Friday
Night
Cloudy with isolated snow showers.
Friday
Moderate snow showers with heavier precipitation under a Puget Sound Convergence Zone.
Friday
Night
Scattered snow showers with heavier precipitation under a Puget Sound Convergence Zone.
Friday
Moderate snow showers, heaviest near the volcanoes. Strong WNW winds.
Friday
Night
Scattered snow showers. Heaviest near the southern volcanoes. Strong WNW winds decreasing.
Friday
Light to moderate snow. Periods of heavier precipitation. Strong and gusty W winds decreasing.
Friday
Night
Scattered showers. Puget Sound Convergence Zone could bring periods of heavier precipitation.
Friday
Light to moderate snow. Periods of heavier precipitation in the morning. Strong and gusty W winds.
Friday
Night
Scattered snow showers. Puget Sound Convergence Zone could bring periods of heavier snow. Strong NW winds decreasing.
Friday
Cloudy with scattered snow showers near the crest.
Friday
Night
Mostly cloudy with isolated snow showers near the crest.
Friday
Cloudy with scattered snow showers, heaviest near the crest. Strong and gusty WNW winds.
Friday
Night
Mostly cloudy to cloudy with isolated snow showers. Heavier near the crest. Strong NW winds decreasing.
Friday
Cloudy with isolated snow showers. Strong and gusty WNW winds.
Friday
Night
Cloudy with isolated snow showers. Strong and gusty NW winds.
Friday
Moderate to occasionally heavy snow. Very strong and gusty NW winds.
Friday
Night
Moderate to occasionally heavy snow. Strong and gusty NW winds decreasing slightly.
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).