Red flag warnings could challenge Northern California further with lightning potential Sunday
There’s not much promising news when it comes to Northern California’s weather outlook for this weekend — for residents or firefighters.
Another round of isolated thunderstorms, “with little to no rainfall,” is in the forecast for parts of the greater Bay Area and the Sacramento Valley beginning Sunday, according to the National Weather Service.
On Saturday, for the Bay Area, fire weather watches from Monterey to Sonoma County were upgraded to red flag warnings as “dry lightning and gusty erratic” winds will come with the thunderstorms, the weather service’s Bay Area office said. The warning is in effect from 5 a.m. Sunday to 5 p.m. Monday and covers areas already charred by the massive LNU, SCU and CZU Complex fires.
That was followed by red flag warnings for a wide swath of the valley “through at least Monday evening.” The warning is for all central Sacramento Valley areas below 1,000 feet — in Butte, Colusa, Glenn, Sutter and Yuba counties — as well as national forests already ablaze from the last round of lightning strikes.
Meteorologists say the remnants of Hurricane Genevieve that spun out over Mexico’s Baja Peninsula will spread into the region Sunday, leading “to the increasing potential for isolated to scattered dry thunderstorms.” A layer of drier air beneath the storms may lead to gusty winds, the weather service warns.
It was an intense series of thunderstorms and thousands of associated lightning strikes that sparked the major, still mostly uncontrolled wildfires that continue to rage across Northern California. The largest of them, the LNU Fire, ignited Monday morning and has grown to nearly 220,000 acres as of Friday morning, sweeping toward Vacaville and Fairfield this week amid extreme fire behavior. At least four have died in the LNU Lightning Complex.
Others, including the SCU, CZU TGU and SHF Lightning Complexes, are part of more than 560 fires burning in the state, Gov. Gavin Newsom said in a Friday briefing.
The incoming thunderstorms are being caused by a moisture system that’s heading north from the Southern California coast, according to the NWS Sacramento office.
In more bad news, smokey skies and poor air quality conditions are expected to last at least into Saturday, according to the NWS, which shows a forecast of “heavy” smoke blanketing a huge portion of the valley, the north foothills, the East Bay and South Bay to start the weekend.
That includes a forecast showing a high of 99 degrees and — not sunny, not cloudy — but simply “smoke” the rest of Friday, followed by “smoke then mostly sunny” Saturday in Sacramento, the latest NWS predictions show.
Residents are urged to limit outdoor time. If you can smell smoke, that means it can be hazardous to your health.
The small nugget of good news is that it appears ultra-hot temperatures are behind us. On Friday, Sacramento Executive Airport topped out at 92 degrees, one degree higher than the normal for this time of year.
Last weekend’s unprecedented mid-August heat wave broke numerous records, and forced the state’s power grid to enact two evenings of rolling outages. Sunday’s reading of 112 degrees at Sacramento Executive Airport marked the hottest August day ever for that site.
It’ll still be several degrees above average, but Sacramento Valley temperatures are expected to drop to the high 90s this weekend and currently forecast to drop to 94 degrees by next Tuesday.
Sacramento only hit a high temperature of 88 degrees Wednesday, according to the NWS, far below the anticipated high of 105 degrees. Wildfire smoke blocking the sun could have accounted for some of that cool-down.
This story was originally published August 21, 2020 at 11:36 AM.
