A strong upper level ridge anchored offshore will maintain dry and mostly sunny conditions in the mountains today. Mid and upper mountain temperatures will be several degrees cooler than over the weekend with freezing levels in the 6500-9000' range across the region. Cooler temperatures will be found near trailheads and the lower slopes thanks to continued temperature inversions. An inland shortwave trough dropping south over the northern Rockies today will cause a spike in northerly alpine winds along the east slopes of the Cascades, mainly north of Lake Chelan. Lowland clouds and fog remains mired in the lowlands and deeper mountain valleys. As the cross-Cascade gradient becomes offshore tonight, look for more low clouds to be pulled through the Cascade Passes Monday night. Brisk NW winds at ridgeline will ease this afternoon.
Tuesday features more of the same except freezing levels will be slightly cooler along the east slopes of the Cascades. A "dry" upper level shortwave approaching from the NW will push some high clouds into the Olympics and north Cascades by Tuesday 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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Monday
Mostly sunny. Areas of low clouds and fog.
Monday
Night
Mostly clear. Areas of low clouds and fog.
Monday
Mostly sunny. Areas of low clouds and fog.
Monday
Night
Mostly clear. Areas of low clouds and fog.
Monday
Mostly sunny. Areas of low clouds and fog.
Monday
Night
Mostly clear. Areas of low clouds and fog.
Monday
Mostly sunny. Areas of low clouds and fog.
Monday
Night
Mostly clear. Areas of low clouds and fog.
Monday
Mostly sunny. Areas of low clouds and fog. Light west winds at Pass level. Moderate west winds at ridgeline.
Monday
Night
Mostly clear. Increasing low clouds overnight near and east of the Pass. Light to moderate east winds at Pass level.
Monday
Mostly sunny. Areas of low clouds and fog. Light west winds at Pass level. Moderate to strong west winds at ridgeline.
Monday
Night
Mostly clear. Increasing low clouds overnight near and east of the Pass. Moderate east winds at Pass level.
Monday
Mostly sunny. Low clouds and fog in the valleys. Moderate NW ridgeline winds becoming strong midday.
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).