A front is currently passing through the Cascades this morning. We are entering a good snow-making period in cool NW flow aloft and strong post-frontal flow that will last until late Friday night or early Saturday morning. Areas of convergence will enhance snowfall totals in the Skagit/Snohomish mountains of the central Cascades including the Hwy 2 corridor through this afternoon. Other areas will see light to moderate snow showers. All areas will see strong west winds throughout the day.
An upper-level shortwave dropping towards us in NW flow aloft will pack a bigger punch later tonight through Friday morning for most areas outside the north Cascades. This will also ramp winds up across the region, with 100 mph gusts possible at many stations through Friday morning. Convergence zone enhancement will begin to shift south a bit toward I-90 and further toward Mt Rainier Friday morning. A secondary area of convergence may form downwind of Vancouver Island mid-day Friday as the low-level wind field becomes more northwesterly.
Expect several feet of snow, 2-4 ft, by Friday afternoon along with the west slopes of the Cascades and Mt Hood with snowfall totals tapering further east of the Cascade crest in part due to strong downsloping.
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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Thursday
Cloudy with light to moderate rain and snow showers. Strong ridgeline winds.
Thursday
Night
Cloudy with moderate snow showers. Strong to extreme ridgeline winds.
Thursday
Cloudy with moderate to occasionally heavy rain and snow showers. Strong ridgeline winds.
Thursday
Night
Cloudy with moderate snow showers. Strong winds.
Thursday
Cloudy with moderate to occasionally heavy rain and snow showers. Strong ridgeline winds.
Thursday
Night
Cloudy with moderate to heavy snow showers. Strong to extreme ridgeline winds.
Thursday
Cloudy with light to moderate rain and snow showers. Strong ridgeline winds. Heavier showers Paradise area.
Thursday
Night
Cloudy with moderate to heavy snow showers. Strong to extreme ridgeline winds. Heavier showers Paradise and White Pass areas.
Thursday
Cloudy with moderate to occasionally heavy rain and snow showers. Strong ridgeline and Pass level westerly winds.
Thursday
Night
Cloudy with moderate to heavy snow showers. Strong Pass level westerly winds, winds strong to extreme at ridgeline.
Thursday
Cloudy with moderate rain and snow showers. Strong ridgeline and Pass level westerly winds.
Thursday
Night
Cloudy with moderate to heavy snow showers. Strong Pass level westerly winds, winds strong to extreme at ridgeline.
Thursday
Cloudy with light to moderate rain and snow showers. Showers heaviest near the Cascade crest. Strong ridgeline winds.
Thursday
Night
Cloudy with light to moderate to heavy snow showers. Strong to extreme ridgeline winds.
Thursday
Cloudy with light to moderate rain and snow showers. Showers heaviest near the Cascade crest. Strong to extreme ridgeline winds.
Thursday
Night
Cloudy with moderate snow showers. Showers heaviest near the Cascade crest. Extreme ridgeline winds.
Thursday
Cloudy with light to moderate rain and snow showers. Showers heaviest near the Cascade crest. Strong to extreme ridgeline winds.
Thursday
Night
Cloudy with moderate snow showers. Showers heaviest near the Cascade crest. Extreme ridgeline winds.
Thursday
Cloudy with light to moderate rain and snow showers. Extreme winds.
Thursday
Night
Cloudy with moderate to occasionally heavy snow rain and snow showers. Extreme 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).