[Update: Red Flag Warning Issued] Slight Chance of Dry Thunderstorms Possible Tonight Through Tuesday

A slight chance of dry thunderstorms could bring new fire starts and gusty winds to Northwest California starting this afternoon, according to the Humboldt County Sheriff’s Office.

The office said there is a low, 10 to 15 percent chance of thunderstorms across the interior starting this afternoon. Chances rise to 15 to 20 percent Tuesday afternoon in Trinity County, which has the highest risk in the region.

Information from the National Weather Service in Eureka indicates monsoonal moisture is expected to move over the area Monday and Tuesday, bringing cloud cover and a chance of isolated showers or thunderstorms. Forecasters said instability in the atmosphere is limited, but a stray thunderstorm cannot be ruled out.

Dry surface conditions will likely keep most rain from reaching the ground, forecasters said, which raises the risk of dry lightning sparking new fires.

The sheriff’s office urged residents to go indoors when thunder roars, stop outdoor activities during storms, and seek shelter inside a building or vehicle.

Hot temperatures are expected to continue through the forecast period, with highs in the 90s across most interior valleys and some areas possibly topping 100 degrees, according to the weather service. Coastal areas will stay cooler, in the high 50s to mid 60s, with overnight fog expected to partially clear by afternoon.

Update: 

The National Weather Service in Eureka has issued a Red Flag Warning for Trinity, northeast Humboldt and southwest Siskiyou counties, in effect from 1 p.m. Tuesday to 2 a.m. Wednesday.

Forecasters said isolated to scattered dry thunderstorms are expected during that window, along with erratic, gusty winds that could reach 50 mph or higher. The combination raises the risk of new fire starts and could cause any fires that do ignite to spread quickly.

The highest thunderstorm chances are in Trinity County, northeast Humboldt County and southwest Siskiyou County, but isolated storms are possible across the wider interior, including Mendocino, Lake and Del Norte counties, according to the weather service.