Very cold air has infiltrated all levels of the atmosphere as of Wednesday morning. Temperatures range from -14F at Washington Pass to the single digits at most NWAC weather stations. The region sits under N flow between a deep trough over the southwestern US and an offshore ridge of high pressure. E flow at the surface continues has generally decreased into the light range, but brought modified arctic air from the interior of the continent into the Puget Sound lowlands. E flow should flip westerly by late afternoon as a weak disturbance drops down the backside of the ridge toward our region. Sunny skies in the morning should give way to increasing mid-level clouds during the afternoon across Washington State.
Light snow associated with the moisture-starved upper-level disturbance dropping down the coastline should increase Wednesday night. The light snow shifts to southern parts of the forecast region Thursday morning before ending. Snowfall should be heaviest in the northern Olympic Mountains and Mt. Baker areas which could pick up 2-4" of very-low-density snow. Most other locations should pick up a trace to 2" of snow. Snow levels should remain at sea level. A brief period of light to moderate NW ridgeline winds should accompany the disturbance. Low-level should shift back easterly and skies mostly clear Thursday afternoon as freezing levels rise to 1000-2000 ft.
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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Wednesday
Sunny and very cold in the morning. Mid-level clouds increase as temperatures moderate in the afternoon.
Wednesday
Night
Cloudy with light snow developing overnight.
Wednesday
Sunny and very cold in the morning. Mid-level clouds increase as temperatures moderate in the afternoon.
Wednesday
Night
Cloudy with light snow developing overnight.
Wednesday
Sunny and very cold in the morning. Mid-level clouds increase as temperatures moderate in the afternoon.
Wednesday
Night
Cloudy with light snow developing overnight.
Wednesday
Sunny and very cold in the morning. Mid-level clouds increase as temperatures moderate in the afternoon.
Wednesday
Night
Cloudy with very light snow possibly developing overnight.
Wednesday
Sunny and very cold in the morning. Mid-level clouds increase as temperatures moderate in the afternoon. Light E winds at the Pass switching W late in the day.
Wednesday
Night
Cloudy with very light snow possibly developing overnight. Light W winds at the Pass switching E by the afternoon.
Wednesday
Sunny and very cold in the morning. Mid-level clouds increase as temperatures moderate in the afternoon. Light E winds at the Pass switching W late in the day.
Wednesday
Night
Cloudy with very light snow possibly developing overnight. Light W winds at the Pass switching E by the afternoon.
Wednesday
Sunny and very cold in the morning. Mid-level clouds increase as temperatures moderate in the afternoon.
Wednesday
Night
Cloudy with very light snow developing overnight.
Wednesday
Sunny and very cold in the morning. Mid-level clouds increase as temperatures moderate in the afternoon.
Wednesday
Night
Cloudy with a slight chance of very light snow developing overnight.
Wednesday
Sunny and very cold in the morning. Mid-level clouds increase late in the day as temperatures moderate 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).