We’re closing out the month of October with a lot of rain across Western Washington.  It has been nearly a year since we have been this wet in Seattle!  We have to go back to November 22, 2011 to find a day with this much rainfall at Sea-Tac Airport. 

As of 10 p.m. Tuesday evening, Sea-Tac recorded 1.15” of rainfall.  That blew the old daily rainfall record of 0.87” out of the park.  The old record was set in 1997.  Check out some of the other rainfall totals from Tuesday.  Some of the heaviest rain fell over the Kitsap Peninsula and along the coast.  Bremerton, Hoquiam, and Forks all saw over 2 inches of rain. 

The satellite image to the left tells the story.  A storm system is spinning off the coast, tapping into a lot of warm moist air.  This moisture is coming from the subtropical Pacific Ocean, just north of the Hawaiian Islands.  That plume of moisture is an atmospheric river; a narrow band of water vapor that transports steady rainfall into the area.  It’s also known as a “pineapple express” because of its tropical origin. 

As this warm moist air comes in from the southwest, it brings snow levels up and drops heavy rainfall over the mountains.  All of that rain makes it into our local rivers, causing them to rise.  The Skokomish River in Mason County is under a Flood Warning with minor flood forecast as it crests on Wednesday.  A Flood Watch continues for rivers in Whatcom, Skagit, Snohomish, King, and Pierce Counties.  The rivers most likely to experience minor flooding are the Skokomish, Stillaquamish, Skagit, Nooksack, White, and Puyallup Rivers.  They will be cresting over the next 24 to 36 hours. 

A Rainy Halloween

 This storm system will continue to pump steady rain our way for Halloween.  Another 0.5” to 1.5” of rainfall is forecast Tuesday night through the day on Wednesday across Puget Sound. 

If you’re dressing up as the Wicked Witch from the Wizard of Oz and don’t want to melt in the rain, there is a little hope Halloween night.  After 5 p.m. the latest computer models coming in are showing the steady rainfall turning over to scattered showers.  We’ll likely see some dry breaks when it’s time for trick-or-treating.  It’s won’t be completely dry, but temperatures will at least be fairly mild with mid 50s. 

Have a safe and Happy Halloween! 

-Sam Argier, KIRO 7 Meteorologist