Two Reasons Parts of Washington State Have Been Unusually Warm

I am not the only one who noticed Washington has been really warm this week. Turns out there are two reasons for this, but both could be ending soon.

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I live in the Tri-Cities area, and we have had multiple days in the 70's, pretty close to 80°. A post from Cooperative Institute for Research in the Atmosphere explains why.

The “Heat Dome” Effect is Over the West

The idea behind it is pretty straightforward once you break it down. A strong high-pressure ridge is sitting over the western U.S. and is acting like a lid on the atmosphere. Air sinks under high pressure, and as it sinks, it compresses and then heats up.

That is why these ridges are often tied to record-breaking heat. They also block clouds and storms, letting sunshine heat the ground, making the heat situation even worse.

Adding to the issue, the jet stream, the fast-moving river of air that steers weather systems, gets pushed north into a big arch around the northwest. That keeps the hot, stable air locked in place for days or longer.

Washington's Rain Getting Redirected North and East

That same ridge not only generates heat; it also acts as a barrier. Storm systems coming in from the Pacific can’t move straight inland like they normally would. Instead, they are forced to go around the ridge of high pressure.

This time, “around” means north.

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Moisture-rich systems, like an atmospheric river, get steered into places like the Pacific Northwest and British Columbia instead. An atmospheric river is basically a long, narrow band of concentrated moisture in the atmosphere.

It is one connected pattern, not two separate events. And when it lines up just right, you get that combo of unusual heat to the south and soaking rain to the north.