A Wet September Storm

It’s already been a wet a cool September. And we have another wet storm on the way.  A few notes:
  • Usually storms in September are weak, bringing only very light rain. This upcoming weekend storm is much stronger than normal for mid September. 
  • The storm is also moving rather slowly, giving most locations about 24 hours of rainfall.
  • The track of the storm is on a line from around Salem, OR to Spokane. 
All of these factors mean a wetter and more widespread rain event. Even folks in the Basin will see decent amounts of rain.  In fact, it’s possible that the driest locations in the state could get the most rainfall. 

Here’s a few of the historically most accurate weather computers and their rainfall forecasts for this event. 






What should jump out at you is that they’re all pretty similar. We’ve seen other events where the computers are all over the place. Not this time. When the computers all agree like this, confidence is very high. 

Here’s a zoomed in forecast from an average of all the other computer forecasts. 




Over 1/2” for just about everyone in eastern Washington, and around an inch predicted for folks in Yakima and Wenatchee.  Portland and Everett are expected to only see about 1/4”. 

Here’s the timeline for the rain. It will start Saturday evening and end Sunday evening. Nearly 100% of the computers agree on this, which is rare.



After this storm, you can see that things dry out considerably. The second half of September probably won’t look like the first half. 








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