A strong front blew through Monday night bringing widespread snow showers, falling snow levels, and strong to extreme Westerly ridgeline winds. That trend will continue through this morning, with the heaviest snow showers focused on the west slopes of the Cascades, the Olympics and the Mt Hood area. Showers will taper for areas further east of the Cascade crest. Those gusty W winds we are seeing in many areas will take a sharp nose-dive towards more moderate or even light winds by mid-day. This will occur as a cold upper trough digs over the PNW and cuts off the strong post-frontal westerly flow. The caveat to the decreasing winds will be the Mt Hood area where strong westerly winds will continue for the remainder of the day. During showers, snow should accumulate in the 1500-2000' range. If you're lucky enough to see sunbreaks today near the Cascade crest, it should be short lived as clouds and showers fill back in.
Colder air will begin to move toward our area overnight. Cold Fraser outflow will begin Tuesday night with some localized gusty NE winds for the mountains near the Canadian border and potentially some light upslope snow showers along the north slopes of the Olympics. That same modified arctic air will begin to squeeze out some lower density snow along the east slopes of the Cascades. While showers shouldn't be particularly heavy, this should squeeze out a few fluffy inches. Mt Hood should pick up the most overnight in this pattern.
On Wednesday, we'll keep that cold air and unstable air mass over us with more scattered light snow showers. Cold easterly flow will begin to increase in the afternoon, setting the stage for some moderate to strong E-SE winds Wednesday night in many areas.
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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Tuesday
Light to moderate snow showers. Strong winds this morning decreasing mid-day.
Tuesday
Night
Cloudy with light snow showers.
Tuesday
Light to moderate snow showers becoming cloudy with scattered light snow showers in the afternoon.
Tuesday
Night
Cloudy with scattered light snow showers.
Tuesday
Moderate to occasionally heavy snow showers this morning, becoming lighter and more scattered in the afternoon. Strong ridgeline winds this morning becoming moderate mid-day.
Tuesday
Night
Cloudy with scattered light snow showers.
Tuesday
Light to moderate snow showers this morning, becoming lighter and more scattered in the afternoon. Heavier showers Paradise and White Pass area. Strong ridgeline winds this morning becoming moderate mid-day.
Tuesday
Night
Cloudy with light snow showers.
Tuesday
Light to moderate snow showers this morning, becoming lighter and more scattered in the afternoon. Strong ridgeline and Pass level W winds this morning becoming moderate mid-day.
Tuesday
Night
Cloudy with scattered light snow showers. Pass level winds turning from light W to light E overnight.
Tuesday
Moderate to occasionally heavy snow showers this morning, becoming lighter and more scattered in the afternoon. Strong ridgeline and Pass level W winds this morning becoming moderate mid-day.
Tuesday
Night
Cloudy with scattered light snow showers. Pass level winds turning from light W to light E overnight.
Tuesday
Light to occasionally moderate snow showers mainly near the Cascade crest this morning, becoming scattered light snow showers in the afternoon. Strong ridgeline winds this morning becoming moderate mid-day.
Tuesday
Night
Cloudy with light snow showers.
Tuesday
Light to moderate snow showers mainly near the Cascade crest this morning, becoming scattered light snow showers in the afternoon. Strong to extreme ridgeline winds this morning becoming moderate mid-day.
Tuesday
Night
Cloudy with light to occasionally moderate snow showers.
Tuesday
Light to moderate snow showers mainly near the Cascade crest this morning, becoming scattered light snow showers in the afternoon. Strong to extreme ridgeline winds this morning becoming moderate mid-day.
Tuesday
Night
Cloudy with light snow showers.
Tuesday
Moderate snow showers this morning, becoming light to moderate in the afternoon. Strong to extreme ridgeline winds slightly decreasing in the afternoon.
Tuesday
Night
Cloudy with light to moderate snow showers. Moderate to 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).