High pressure trapped smoke, its effects over the weekend


A warm, stable air mass stuck in place over Washington

Mid-level hills are firmly anchored over Washington for the next 5-7 days, providing warm temperatures, clear skies, and light winds for nearly the entire state. When we get patterns with very little wind associated with it, the daily wind patterns are dictated by the terrain. In the afternoon, hot air along the mountain slopes tends to rise, creating slope winds. At night, the air cools more quickly in the mountains and drains through the valleys, creating steep winds. These sloping winds at night are the primary driver for bringing low-level smoke into the Puget Sound region, as well as into the Wenatchee Valley.

The Omega Block pattern is responsible for our warm, dry pattern with light winds this week

With very little wind outside the daily slope/slope pattern, smoke can easily get trapped in valleys and sewers. The worst smoke effects this weekend will be along Highway 2, spreading east from Skykomish, across Lake Wenatchee, and downhill all the way to Wenatchee City. Highly concentrated smoke will also spread west from Skykomish, down through Gold Bar and Monroe, with less intense but still impactful smoke in northern King County and Snohomish County in the Puget Lowlands. Packwood will continue to see unhealthy levels of smoke from the Goat Rocks fire, and moderate to sometimes unhealthy smoke levels are possible in the Methow Valley from the fires in the North Cascades.

Satellite imagery in the morning shows fog in Low Puget, with thick smoke along Hwy’s 2 and 12. More spreading smoke appears over the North Cascades

If you’re wondering if this weather pattern is normal, it’s definitely not. Record high temperatures were set in several locations across the state this week, with Seattle setting a record for most consecutive days above 75 degrees Fahrenheit for the month of October!

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