Note: This article is using the meteorological definition for fall, which is September 1 to November 30. The first half of meteorological fall is September 1 to October 15.
The weather pattern over the Western United States has been dominated by persistent upper level ridging for several weeks, leading to above average temperatures and below average precipitation values for much of the region.
Many places west of the Cascades in the Pacific Northwest observed their warmest start to fall in history as a result of this pattern. Meanwhile, the ridge by and large kept the jet stream to the north, sending copious amounts of rain into Southeast Alaska.
Both Seattle and Portland were among the cities who experienced record warmth. In Seattle, the mean temperature for the first half of fall (September 1 to October 15) was 64.0°, beating the old record set in 2020 by 0.7°. The average high for the period also set a record at 74.1° but the average low only came in 3rd.
The mean temperature in Portland was also record setting at 67.5°, beating out the 66.8° observed in 1952. The average low was 56.9° to barely set a new record warmest while the average high for the first half of fall 2022 was 78.1° to come in third place.
The northward trajectory of the jet stream has also served to keep precipitation out of the Pacific Northwest. Moderate drought conditions are now being felt in much of Western Washington on top of the preexisting drought in much of Oregon.
Easterly wind events helped to fuel fires on the west slopes of the Cascades in October, sending smoke into the Interstate 5 corridor. While there are many fires, the Nakia Creek Fire north of Camas and the Bolt Creek Fire east of Monroe are especially notable for sending smoke into the Portland and Seattle metro areas. When the wind isn’t blowing, the smoke slowly filters into lowland areas keeping the air quality poor.
A big pattern change is forecast later this week, bringing cooler temperatures and a lot more rain to the Pacific Northwest. Highs in the 50s and 60s are likely along I-5 with a couple inches of rain possible in the lowlands west of the Cascades over the next week or so.
For coverage about the upcoming pattern change for the Tri-Cities area, head over to this article from Tuesday.
