The North Bay is experiencing a rare mixture of weather phenomena on Thursday as cold temperatures bring rain that turns to snow in some areas while thunderstorms are forecast for the evening.
A mixture of hail and graupel -- slushy snow pellets -- pelted Vallejo around noon and more hail was reported in Santa Rosa and Rohnert Park around 1:30 p.m. The Sonoma County coastal mountains are experiencing a peppering of snow as well.
Solano County has rain forecast for the afternoon and evening, with a possibility of isolated thunderstorms, according to Courtney Carpenter, a meteorologist for the National Weather Service.
"Because such cold air is present, any heavier snow or thunderstorm that pops up will have the potential to drop accumulating small hail or graupel," Carpenter said.
In Sonoma County, temperatures will reach freezing or below by Friday morning, according to Brian Garcia, another meteorologist with the weather service. A freeze warning is in effect from noon Thursday to 9 a.m. Friday. The Sonoma Coastal Range mountains will pick up "a couple inches likely" of snow, according to Garcia.
A winter storm warning is in effect for mountains in Sonoma, Napa and Solano counties.
The Mayacamas and Vaca Mountain ranges that span both Napa and Solano counties could see accumulated snow of up to 8 inches.
"There is an outside shot, less than about 10 percent, that the highest elevations pick up a foot or more of snow," said Garcia.
"One of the strongest thunderstorms overnight may cause a few snowflakes to get pushed down to sea level," he added, saying that there is a 10 percent chance that snow could mix with rain in lower elevations.