Across California, the warning means there will be power outages for thousands

Potentially dangerous weather will prevail across much of California over the weekend, with gusty winds, red flags and the threat of additional power shutoffs – already in effect for thousands – to prevent deadly wildfires from starting.

From Redding to Riverside, forecasters are warning of strong offshore flow through at least Saturday, with gusts of up to 40 and 50 miles per hour drying out much of California and triggering utility shutoffs in the most vulnerable areas. In Southern California, conditions give rise to the infamous Santa Ana winds, which are often the cause of some of the region's most dangerous late-season fires.

According to a Red Flag Warning issued for Southern California, “if a fire ignites, conditions will be favorable for rapid fire spread and extreme fire behavior that would endanger life and property.”

Across Northern California, Pacific Gas and Electric initiated a public safety shutdown Thursday afternoon, with about 13,000 customers shut off and 7,000 still under consideration for additional shutdowns Friday, PG&E's latest update said. The shutoffs were initiated throughout the northern Sacramento Valley, along the inland Bay Area and even into Santa Barbara County, according to the utility's outage map.

Southern California Edison, which provides power to about 15 million people in the Southland, said it was considering similar power shutoffs for more than 120,000 customers in seven counties, including Los Angeles, Orange and San Bernardino. About 400 customers in Inyo and Mono counties have already been disconnected “due to the increased risk of wildfires,” the company reported.

The state's three major investor-owned utilities, PG&E, SCE and San Diego Gas & Electric, have pursued a strategy over the last decade of shutting down their lines where there is a risk that their equipment will fail in high winds, causing one Start a fire. Many of California's deadliest and most destructive fires were started by utility equipment.

Diane Castro, a spokeswoman for Southern California Edison, said shutdowns were possible through Saturday afternoon. PG&E said the shutdowns are expected to be required through Saturday.

Late Thursday, winds began to increase across the state as a low pressure system moved across the state from the Pacific Northwest, particularly in Northern California, where the weather service reported gusts of 63 mph at Mt. St. Helena and 45 mph in Los Vaqueros recorded reservoir and 48 mph at Mt. Diablo.

Much of the Bay Area and Sacramento Valley will remain under an advisory through Saturday evening, with wind gusts of up to 55 and 65 mph expected along some of the highest peaks and sustained winds of up to 25 to 35 mph, according to the weather service .

“Despite recent cool weather and high humidity, we expect a widespread and persistent offshore wind event that will likely result in fuel drying out very quickly,” the region’s alert said.

While offshore flow will cause overnight temperatures to rise slightly, displacing any influence from the marine layer, overall temperatures in the region will not rise, said Joe Merchant, a meteorologist with the National Weather Service in Monterey.

“Typically, people associate fire weather concerns with hot temperatures … (but) temperatures will feel relatively normal for this time of year,” Merchant said. “That doesn’t mean we can’t have critical fire weather concerns.”

He said plants and bushes in the area had record low moisture levels, meaning a fire could spread quickly.

Read more: The airport fire destroyed his house. Did the help arrive on time?

On Thursday, wind gusts peaked at 56 miles per hour in northern Los Angeles County at Lake Palmdale, with high winds recorded along the Central Coast and into the Antelope Valley, the weather service said. Conditions were expected to worsen on Friday.

The Santa Ana wind pattern is causing red flags in the mountains and valleys of Los Angeles and Ventura counties Friday and Saturday, the weather service warned.

“Gusts between 30 and 45 mph will be common across much of Los Angeles and Ventura counties, with isolated gusts up to approximately 50 mph,” the red flag warning said. “The wind will be strongest in the valleys and mountains.”

These strong winds coupled with low relative humidity “will promote rapid fire growth and erratic fire behavior,” the warning says.

The valleys and mountains of San Bernardino and Riverside counties are also under an advisory through Saturday.

In Orange County, the Santa Ana Mountains are facing similar wind conditions, but forecasters said the recent airport fire destroyed much of the available brush, making the area less vulnerable to fire spread.

Further east, parts of Southwest California aren't necessarily facing these critical fire conditions, but gusty winds – also gusts up to 50 and 60 mph – are still expected through Saturday. A wind advisory for the Mojave Desert, Coachella Valley and interior warns that tree limbs could fall, unplanned power outages are possible and driving could be difficult, especially for high-profile vehicles.

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This story originally appeared in the Los Angeles Times.