November, which marks the start of flood season in the Northwest, is just around the corner. And the National Weather Service says there is high potential for rivers to burst their banks from now through February.
This winter will bring what is known as a“neutral” weather pattern; we won't see the milder El Niño nor the wetter, windier La Niña this winter. But that hardly means we get a break.
A neutral winter can mean trouble for those who live or work near flood plains in western Washington as it brings the highest number of so-called “Pineapple Express” events during which an atmospheric river forms off the coast.
"Most of our significant flood events involve atmospheric rivers. They bring a lot of precipitation in a relatively short amount of time—I'm talking two, maybe three days, something like that," said meteorologist Ted Buehner.
Along with all that water at sea level and in the lowlands, Buehner says, the warm air carried in by the atmospheric river pushes freezing levels up to 7,000 feet or even as high as 9,000 feet. And that means more rain coming from the mountains as well, with little to no snow pack absorbing all the moisture.
The sustained heavy rainfalls created by those dynamics is the most frequent cause of major flooding. But it's worth noting that last year was deemed a neutral winter by the Weather Service, too, and there were no major events.
Still, the National Weather Service and local governments are urging people to prepare now by getting emergency plans and disaster kits ready. Many jurisdictions also have sandbags available for people with flood-prone properties.
