By Evan Bush and Hal Bernton, Seattle Times

It’s a forecast so hot that it left some seasoned meteorologists initially in disbelief.

Weekend temperatures are expected to approach 100 degrees in Seattle, top 109 in Portland and reach 115 in Eastern Washington — threatening to topple historical records and upend people’s lives.

“Is this just the models being wonky, or is this a real deal?” said Joe Boomgard-Zagrodnik, a postdoctoral researcher in agricultural meteorology at Washington State University, describing his reaction to initial temperature readouts.

When he assessed the data himself, “it was jaw-dropping.”

Climate scientists and meteorologists say the forthcoming heat wave — which could persist into next week — is a manifestation of climate change and a concerning signal of what they expect more frequently in the Pacific Northwest, which is poorly adapted to extreme heat.

“This is pretty early in the season to be experiencing so many days where temperatures are record breaking. It’s worrisome. It’s just June,” said Deepti Singh, a climate scientist and associate professor at WSU Vancouver. “This should be a warning sign for us that we’re experiencing the impacts of climate change right now.”

The science of heat

The weather pattern bringing scorching hot temperatures to the Northwest is the result of a large ridge of high atmospheric pressure sometimes called a heat dome.

High pressure systems suppress storms, offering clear skies with full sun, and they act as a cap and trap heat near the surface.

“Air is sinking and it’s warming as it sinks,” Boomgard-Zagrodnik said.

This weather pattern itself is extreme, but not unprecedented, said Nick Bond, an atmospheric scientist at the University of Washington who also serves as the state’s climatologist. He does not predict that patterns of pressure will change in the coming decades, though he acknowledges that research is still developing.

What has changed is that the region has warmed nearly 2 degrees since 1900, according to the 2018 national climate assessment by U.S. Global Change Research Program, crafted with input from 13 federal agencies.

“Now, when you have heat waves, when that baseline has moved up … it’s that much more severe,” Bond said.