California's utility shuts off power in 12 counties as Diablo winds increase wildfire risk

SAN FRANCISCO (AP) — A California utility has shut off power in 12 counties in the northern part of the state as a strong “Diablo wind” — notorious for its hot, dry gusts in the fall — has increased the risk of downing power lines could cause a wildfire.

About 13,000 customers woke up without power Friday after Pacific Gas and Electric shut off power.

The “Diablo Wind” According to the National Weather Service, sustained winds of 35 mph (56 km/h) are expected in many areas, with possible gusts of over 65 mph (104 km/h) on mountain peaks. Strong winds are expected to continue for part of the weekend.

The utility began cutting power Thursday to customers in 12 counties, including Alameda, Contra Costa, Napa, Solano and Sonoma in the Bay Area, as well as some customers farther north in Colusa, Glenn, Tehama and Shasta counties, PG&E said.

In total, about 20,000 customers could temporarily lose power over the next few days, PG&E said in a statement Thursday.

Meteorologists issued fire warnings through Saturday from the central coast through the San Francisco Bay Area to northern Shasta County, not far from the Oregon border.

“This could be the most significant wind event so far this year,” said meteorologist Brayden Murdock of the service’s Bay Area office. “We want to tell people to be careful.”

During a Diablo wind, which is common in the fall, the air is so dry that relative humidity drops, vegetation dries out and is ready to burn. The name – “Diablo” is Spanish for “devil” – is used informally for a hot wind that blows inland toward the coast near the San Francisco region as high pressure builds to the west.

Targeted power shutdowns were also possible in Southern California, where another notorious weather phenomenon, the Santa Ana winds, is expected on Friday and Saturday.

Santa Anas are dry, warm, gusty northeasterly winds that blow toward and offshore from the interior of Southern California, moving in the opposite direction of the normal overland flow that carries moist air from the Pacific into the region.

The National Weather Service issued red flag warnings for the valleys and mountains of Los Angeles County, parts of the Inland Empire and the San Bernardino Mountains.

Winds in the Los Angeles area will not be as strong as in the north, with gusts between 25 and 40 miles per hour (40 and 64 km/h) possible in mountains and foothills, said Mike Wofford, a meteorologist at the weather service's Los office Angeles.

The strongest winds were recorded in the Santa Monica and San Gabriel mountains, where there were gusts between 45 and 55 mph Friday and isolated gusts of up to 60 mph, he said.

“The humidity is drying out and we have winds. If we had a spark of fire, it could spread very quickly given the current conditions,” Wofford said.

Meanwhile, snowfall is forecast for the mountain peaks around Lake Tahoe, where up to 2 inches (5 centimeters) was forecast by Friday morning, according to the National Weather Service in Reno, Nevada. Wind gusts of up to 70 miles per hour (113 km/h) could occur around Lake Tahoe.

The service also issued its first freeze warning of the season along the Sierra's eastern front, effective from 2 a.m. to 9 a.m. Friday from south of Carson City north through Reno into Lassen, Sierra and Plumas counties in California, where temperatures rose to Low temperatures could drop to 20s Fahrenheit (-5 degrees Celsius).

“Frost and freeze conditions could kill crops and other sensitive vegetation and potentially damage unprotected outdoor plumbing,” the service said.