The energy and moisture associated with a large upper-level trough over the western US have shifted south of our region. Moderate and locally strong E and NE ridgeline winds continue through the morning in the moderate range in some locations near the Cascade Crest and along exposed ridgelines east of the Cascade Crest such as the Wenatchee Mountains. These winds should squeeze out a few snow flurries with very limited moisture available before skies clear more fully as the day progresses. Fraser River outflow peaked late Monday night and should gradually decrease, but the influx of modified arctic air has brought temperatures to near or below freezing in the Puget Sound lowlands early this morning. Mountain temperatures range from below zero at Washington Pass into the single digits and low teens. Temperatures should rise into the teens in most mountain locations with lower elevation locations getting into the low 20s.
On Tuesday night, expect the coldest temperatures of the week with strong radiational cooling under clear skies and mostly light winds. Light to moderate E flow through the mountain gaps should continue to ease. Inversions should form overnight and linger into Wednesday morning. Most locations can expect a very cold start to the day. By Wednesday afternoon temperatures begin to moderate slightly and freezing levels rise to around 1000 ft as light easterly low-level flow switches westerly ahead of a weak disturbance dropping south on N flow aloft.
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 cloudy, becoming partly cloudy late in the day. Cold.
Tuesday
Night
Scattered low clouds early, then becoming mostly clear. Very cold.
Tuesday
Partly cloudy early with a chance of snow flurries early, then becoming mostly sunny by late morning. Cold.
Tuesday
Night
Mostly clear. Very cold.
Tuesday
Partly cloudy early with a chance of snow flurries early, then becoming mostly sunny by late morning. Cold.
Tuesday
Night
Mostly clear. Very cold.
Tuesday
Partly cloudy early with a chance of snow flurries early, then becoming mostly sunny by late morning. Cold.
Tuesday
Night
Mostly clear. Very cold.
Tuesday
Partly cloudy early with a chance of snow flurries early, then becoming mostly sunny by late morning. Cold. Light occasionally moderate E wind at the Pass.
Tuesday
Night
Mostly clear. Very cold. Decreasing light E wind at the Pass.
Tuesday
Partly cloudy early with a chance of snow flurries early, then becoming mostly sunny by late morning. Cold. Light to moderate E wind at the Pass.
Tuesday
Night
Mostly clear. Very cold. Decreasing light to occasionally moderate E wind at the Pass.
Tuesday
Mostly cloudy early with a chance of snow flurries, then increasing sunshine in the afternoon. Very cold.
Tuesday
Night
Mostly clear. Very cold.
Tuesday
Mostly cloudy early with a chance of snow flurries, then increasing sunshine in the afternoon. Very cold. Strong winds gradually decreasing in the Wenatchee Mountains.
Tuesday
Night
Mostly clear. Very cold.
Tuesday
Mostly cloudy early with a chance of snow flurries, then increasing sunshine in the afternoon. Very cold. Strong wind gusts likely near the Cascade Crest.
Tuesday
Night
Mostly clear. Very cold.
Tuesday
Scattered clouds and snow flurries early, then becoming mostly sunny. Cold.
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).