The National Weather Service Saturday afternoon upgraded a fire weather watch to a red flag warning, which will be in effect Sunday morning through Monday for the Santa Lucia Range and Los Padres National Forest as well as for interior of Monterey County including Pinnacles National Park due to the possibility of thunderstorms.
A surge of monsoon humidity could bring thunderstorms and a risk of dry lightning across the Central Coast and Bay Area Sunday through Monday, according to the National Weather Service.
“Thunderstorms will be a mix of dry and wet, but given the dry fuels, any lightning strikes will be problematic,” the weather service wrote in the warning. “The threat of thunderstorms lessens Monday afternoon as the humidity moves north.”
The warning will be in effect from Sunday 11 a.m. to Monday 5 p.m. A red flag warning was also issued for the Santa Cruz Mountains, Diablo Range, East Bay Hills and North Bay Mountains from 5:00 p.m. Sunday to 5:00 p.m. Monday.
A severe storm system moved through the San Francisco Bay and Monterey areas in August 2020, packing a combination of dry lightning and high winds that sparked several devastating wildfires across the region, including the River Fire south of Salinas and the CZU, LMU and SCU August lightning complexes, destroying thousands of homes and burning nearly a million acres. While a red flag warning means critical fire weather conditions are present, the weather service does not expect to see the same results as last year’s lightning-triggered wildfires.
“It has nothing to do with the August 2020 event,” said National Weather Service meteorologist Drew Peterson. “It is possible that we will see new fire starts if we receive these lightning strikes. However, we do not have the same prerequisites.
Specifically, it was hot and dry during last summer’s event, which made it easier for the fires to start and spread, Peterson said, adding that Tropical Storm Fausto also played a role.
“Yes, we are in a drought and the fuels are dry; however, it’s July and we’ve had a marine layer on the coast almost every day,” Peterson said. “It brought drizzle and cooler temperatures which would make it harder to start fires along the coast. And we don’t expect a massive burst of heat or dry conditions when we get this lightning.
Monsoon events typically impact the Bay Area every two to three years, Peterson said. They occur when a high pressure system forms over the Four Corners region, where Arizona, Colorado, New Mexico and Utah meet. The system rotates clockwise over the Gulf of Mexico, northern Mexico, Arizona, New Mexico and southern Texas, and at times there is enough humidity that it reaches California.
“What we’re dealing with is just one of those cyclic-type monsoon events that can generate isolated but potentially scattered high-base thunderstorms,” Peterson said. “And with that, we could see in the order of one to 20 lightning strikes. It could be more or we couldn’t see any.
Peterson said he wouldn’t be surprised if lightning starts fires, but absent the hot, dry conditions that prevailed during the event last summer, they won’t spread as quickly.