A passing disturbance ushered in cooler air from the interior on E and NE winds Thursday night. It didn't have much moisture, and the only reported snowfall was a trace in Zigzag, just west of Mt. Hood. The reinforcing shot of cold air dropped temperatures 5-10F in most areas on both sides of the Cascades. The coldest air remains within the cold pool east of the Cascade Crest, but over the next 24 hours, this cold air will be less decoupled from the rest of the atmosphere. Because the low-level E winds are partially driven by temperature contrasts, the E flow through the mountain gaps has decreased. Meanwhile, ridgeline winds increase into the light to moderate ridgeline range throughout the day Friday for areas near the Cascade Crest in Washington State, then Mt Hood from mid-morning through the evening hours.
Friday night, E winds ease throughout the region, then switch N, before switching WNW on Saturday. This wind shift allows a weakened offshore ridge to raise freezing levels first for the Olympics and then for the southern Washington Cascades Friday night through Saturday. Meanwhile, a thickened cold air pool insulates areas near and east of the Cascade Crest from the gradual warming trend.
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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Friday
Sunny.
Friday
Night
Clear skies. Increasing temperature inversions.
Friday
Sunny. Colder.
Friday
Night
Clear skies. Increasing temperature inversions.
Friday
Sunny. Colder.
Friday
Night
Clear skies. Increasing temperature inversions.
Friday
Sunny. Much colder and breezier in areas near the Cascade Crest.
Friday
Night
Clear skies. Increasing temperature inversions.
Friday
Sunny. Cold. Light to moderate ridgeline and light E wind at the Pass.
Friday
Night
Clear skies. Increasing temperature inversions. Light ridgeline and E wind at the Pass.
Friday
Sunny. Cold. Light to moderate ridgeline and E wind at the Pass.
Friday
Night
Clear skies. Increasing temperature inversions. Light ridgeline and light to moderate E wind at the Pass.
Friday
Sunny. Cold. Strong temperature inversions.
Friday
Night
Clear. Cold. Strong temperature inversions.
Friday
Sunny. Cold. Moderate temperature inversions. Moderate ridgeline wind gusts.
Friday
Night
Clear. Cold. Moderate temperature inversions.
Friday
Sunny. Cold. Moderate temperature inversions. Moderate ridgeline wind gusts.
Friday
Night
Clear. Cold. Moderate temperature inversions.
Friday
Sunny. Cooler. Ridgeline winds increase into the moderate range.
Friday
Night
Clear. Decreasing light to moderate winds in the evening become light.
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).