Another round of relentless, hazardous heat forecast across the West

Another round of significant heat across California’s interior is expected to bring potentially dangerous conditions back to the state, with weather officials warning of “relentless” heat risk over the Southwest beginning this weekend.

The National Weather Service warned of a mid-July heat wave building across the western United States — including the majority of inland California, most of Nevada and parts of Arizona, Oregon and Idaho — with “hazardous heat” expected from Saturday through at least Tuesday.

The “multi-day nature of this event will create dangerous conditions,” the weather service’s alert said.

“We just got done from a very significant heat wave the past two weeks, and unfortunately we do see a warming trend again,” said Alex Tardy, a National Weather Service meteorologist in San Diego. It’s not as severe, Tardy said, “but still a significant warming trend.”

A heat dome — a ridge of high pressure in the upper level of the atmosphere — will take shape in the next few days, Tardy said, causing dramatic warming as that high-atmosphere pressure essentially traps hot air.

“Thursday and Friday, it starts to build in over our region,“ Tardy said, with the heat dome expected to peak over the weekend as its center settles above inland California.

The length of this heat wave isn’t yet clear, but the Climate Prediction Center warned that “above-normal temperatures are likely to persist across much of the West and Great Plains into early August.”

An excessive heat watch has been issued for much of inland Southern California, warning of “dangerously hot conditions with temperatures up to 95 to 110 possible” from Friday through next Wednesday. Overnight low temperatures are generally not expected to drop below the 70s, the weather service warned.

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In the Mojave Desert, a heat watch has also been issued for Saturday and Sunday, where highs will range from 110 to 115; Death Valley National Park can expect temperatures above 120, the warning said.

The hot, dry period will again bring increased fire risks, officials said.

“Hot temperatures, dry fuels and occasional gusty winds are likely to maintain an enhanced wildfire risk for parts of the Pacific Northwest, Great Basin and California,” the Climate Prediction Center warned.

The last heat wave, which dragged on for more than a week in much of California, fueled a surge in wildfire activity across the state, engulfing several buildings, prompting evacuations and causing the first fire death of the year.