Autumn officially arrives tonight at 11:50 PM, and for the final day of summer, weather conditions will be quite beautiful. Look for high temperatures on this Friday to climb into the upper 60s to mid 70s under partly cloudy to mostly sunny skies.
Much like Friday, Saturday will feature passing clouds and sunshine with comfortable high temperatures warming into the upper 60s to mid 70s. Although a majority of the day on Saturday will feature partly cloudy skies, by the late afternoon and evening hours, mostly cloudy skies will become draped over eastern Washington and northeast Oregon.
A much more potent storm system will begin to influence the Pacific Northwest on Sunday. Areas west of the Cascades will be quite soggy to wrap up the weekend. Most of our forecast area outside of the Cascade Mountains will stay dry on Sunday, although a slight chance of rain showers exists for the Yakima and Kittitas Valleys. High temperatures on Sunday will return to the upper 60s to low 70s under cloudy skies.
An atmospheric river approaching from the south southwest will provide the Pacific Northwest with our first significant rainfall of the year on Monday. As is typically the case, areas along and west of the Cascades will bear the brunt of the rainfall with precipitation amounts potentially being measured by the inch! For eastern Washington and northeast Oregon, spotty showers will dominate the first day of the workweek with cloudy skies and highs into the upper 60s to low 70s.
Clouds will stay dense on Tuesday although showers appear as if they will be less numerous. A more robust storm system will provide the potential for more persistent rainfall on Wednesday.
Meteorologist Jefferson Donovan
KEPR/KIMA Forecast Team