Surprise spring storms spew hail, snow

A rare bout of late spring thunder, lightening and hail moved across parts of the Bay Area Sunday, pushed along by a low-pressure system that also brought snow to the Sierras.

The system powered up early Sunday afternoon as a line of thunderstorms developed over central Napa County, according to National Weather Service meteorologist Will Pi.

The storms materialized along a line that stretched from roughly Santa Rosa to Calistoga and began moving southwards towards Solano County from there, Pi said.

The chaotic weather system is the result of low pressure and cold temperatures in the upper atmosphere that mingled with the relatively warm surface temperatures to create “a very unstable air mass,” according to Pi.

The most heavily impacted areas can expect sustained winds of up to 25 mph and gusts up to 40 mph, in addition to more thunder, lightening, rain and maybe hail.

Rain totals of up to a quarter of an inch are also expected in the hardest hit areas.

Pi said:

“It’s rare for this time of year. … Sometimes you see it in April and May.”

The system moved inland across Contra Costa County, and the region had a chance of catching more showers until about midnight.

As the storms move quickly to the east, Sierra elevations above 5,000 feet may see from 5 to 10 inches of snow and a winter weather advisory is in effect for areas around Lake Tahoe, Pi said.