We have a battle of air masses, easterly flow and temperature inversions across the mountains this morning. It's quite warm with temperatures in the 40s to the west of the Cascade crest, with areas near the crest and further east mired in the 20s along with low clouds that extend up to most 5000-7000'. It's also quite windy with S-SE winds in many areas with strong offshore gradients helping to drive the colder air through the major Cascade gaps. Outside of the low clouds, we'll see a weak frontal system will spread patchy high clouds over the region today en route to a high overcast tonight.
The frontal system will begin to fall apart overnight just offshore, but a new shortwave feature should travel along the quasi-stationary boundary and help lift the system to the NE, clipping the Olympics and northwest Cascades with a quick shot of precipitation, and much lighter amounts elsewhere. Snow levels should come down to 3500-4500' for areas west of the Cascade crest with precipitation. Areas like Snoqualmie could see a light wintry mix in the morning with some light freezing rain but any accumulations should be very light. The system will pass through Thursday afternoon without much fanfare as we begin to enter another quiet spell of weather.
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
Partly sunny with filtered sunshine in the morning, becoming overcast with increasing high clouds late morning. Moderate to strong ridgeline winds.
Wednesday
Night
Cloudy with light rain and snow developing late. Moderate ridgeline winds.
Wednesday
Partly sunny with filtered sunshine in the morning, becoming overcast with increasing high clouds in the afternoon. Moderate to strong ridgeline winds.
Wednesday
Night
Cloudy with a chance of light rain and snow developing late. Moderate to strong ridgeline winds.
Wednesday
Partly sunny with filtered sunshine in the morning, becoming overcast with increasing high clouds in the afternoon. Moderate ridgeline winds.
Wednesday
Night
Cloudy. Moderate ridgeline winds.
Wednesday
Partly sunny with filtered sunshine in the morning, except areas of low clouds and colder temperatures lower slopes near the crest including White Pass. Becoming overcast with increasing high clouds in the afternoon. Moderate to strong ridgeline winds.
Wednesday
Night
Cloudy. Colder east side of the zone. Moderate ridgeline winds.
Wednesday
Areas of low clouds especially near and east of the Pass. Light flurries possible. Becoming overcast with increasing high clouds in the afternoon. Moderate SE Pass level and ridgeline winds.
Wednesday
Night
Cloudy. Periods of moderate SE Pass level and ridgeline winds.
Wednesday
Areas of low clouds especially near and east of the Pass. Light flurries possible. Becoming overcast with increasing high clouds in the afternoon. Moderate to strong SE Pass level and ridgeline winds.
Wednesday
Night
Cloudy. Moderate SE Pass level and ridgeline winds.
Wednesday
Partly sunny higher terrain near Washington Pass, cloudy further east. Occasional light flurries. Becoming overcast with increasing high clouds in the afternoon.Periods of moderate ridgeline winds.
Wednesday
Night
Cloudy. Periods of moderate ridgeline winds.
Wednesday
Cloudy with periods of light flurries. Periods of moderate ridgeline winds.
Wednesday
Night
Cloudy. Periods of moderate ridgeline winds.
Wednesday
Cloudy with periods of light flurries. Periods of moderate ridgeline winds.
Wednesday
Night
Cloudy. Periods of moderate ridgeline winds.
Wednesday
Moderate ridgeline winds, occasionally strong foothill gaps and west side of the mountain.
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).