Light winds, mostly dry conditions, and cold temperatures create ideal conditions to enjoy the recent low-density snowfall. The Pacific NW sits in weak NW flow aloft as our recent trough slides eastward. Most NWAC stations start Tuesday in the 10s, but inversions in deep valleys of the northeast Cascades and Washington Pass currently sit at a frigid -6F. Most areas can expect sunny skies in the morning with very light winds. Cumulus clouds build up in the afternoon, with just enough instability in the southern Cascades to provide a threat of isolated snow showers. In the Mt Hood area, this could bring an inch of snow under a slow-moving snow shower in some areas.
Tuesday night, expect clearing skies and cold temperatures once again, with cold air pooling in deep valleys. Winds won't be quite as light as Monday night, so temperatures might not drop quite as low.
On Wednesday, a dry and very subtle shortwave moves over the area and slightly increased light W or WNW ridgeline winds. Expect another sunny, chilly start to the day with mostly cloudy skies focused on the west slopes of the Cascades 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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Tuesday
Mostly sunny with the exception of light upslope snowfall along the foothills of the northern Olympics. Becoming partly to mostly cloudy with cumulus build-up in the afternoon.
Tuesday
Night
Mostly clear with cold air pooling in valleys and some valley fog.
Tuesday
Mostly sunny in the morning, then becoming partly cloudy in the afternoon.
Tuesday
Night
Mostly clear with cold air pooling in valleys and some valley fog.
Tuesday
Mostly sunny in the morning, then becoming partly cloudy in the afternoon.
Tuesday
Night
Mostly clear with cold air pooling in valleys and some valley fog.
Tuesday
Mostly sunny in the morning, then becoming partly to mostly cloudy in the afternoon with isolated light snow showers.
Tuesday
Night
Mostly clear with cold air pooling in valleys and some valley fog.
Tuesday
Mostly sunny in the morning, then becoming partly cloudy in the afternoon. Light ridgeline and variable shifting W wind at the Pass.
Tuesday
Night
Mostly clear with cold air pooling in valleys and some valley fog. Light ridgeline and W wind at the Pass.
Tuesday
Mostly sunny in the morning, then becoming partly cloudy in the afternoon. Light ridgeline and variable shifting W wind at the Pass.
Tuesday
Night
Mostly clear with cold air pooling in valleys and some valley fog. Light ridgeline and W wind at the Pass.
Tuesday
Mostly sunny in the morning with a strong inversion. The cold air pool moderates late morning and partly cloudy skies develop in the afternoon.
Tuesday
Night
Mostly clear with cold air pooling in valleys.
Tuesday
Mostly sunny in the morning with cold air pooled in valleys, moderating by late morning. Partly cloudy in the afternoon.
Tuesday
Night
Mostly clear with cold air pooling in valleys.
Tuesday
Mostly sunny in the morning with cold air pooled in valleys, moderating by late morning. Mostly cloudy with an isolated snow shower possible in the afternoon.
Tuesday
Night
Clearing skies with cold air pooling in valleys.
Tuesday
Mostly sunny in the morning with cold air pooled in valleys, moderating by late morning. Mostly cloudy with an isolated snow shower possible in the afternoon.
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).