Residents of the upper Central Valley were told to seek shelter immediately Tuesday afternoon as a turbulent weather system moved across Northern California and triggered the first tornado warnings of the year for the region, the National Weather Service said.

The weather service’s offices in Sacramento and Hanford issued tornado warnings about 12:20 p.m. and then again about 1:45 p.m. A funnel cloud was spotted above Turlock but no one witnessed it touch down, said NWS forecaster Brooke Bingaman.

The storm dropped up to three-quarters of an inch of rain in 30 minutes at one point, flooding streets in downtown Sacramento. Lightning exploded a tree and damaged three homes, Bingaman said.

⚠️ Take Cover! Tornado Warning including Winton CA, Cressey CA, Snelling CA until 1:45 PM PDT pic.twitter.com/CObjVyFwne — NWS Hanford (@NWSHanford) March 21, 2017


California averages about 10 tornadoes a year, most, if not all, on the low end of the Enhanced Fujita scale that goes from 0 to 5, officials said.

The tornado warnings come as the state transitions out of its traditional rainy period into the warmer spring, Bingaman said.

That transition is fraught with turbulence, she said.

“We still have cold winter storms moving over California and those storms have very cold air up above. But we have sunshine and the surface air gets really warm,” she explained. “Warm air wants to rise, cold air wants to sink. That makes the atmosphere topsy turvy.”


In Oakdale where lightening hit a tree and caused a fire. Three homes damaged. Power out in the area. pic.twitter.com/Gda1ZEWPqG — Erin Tracy (@ModestoBeeCrime) March 21, 2017

Hail the size of marbles was reported in Oakdale and wind gusts were clocked above 40 mph in the Sacramento Valley, the weather service said.

Another storm series is expected across the region over the weekend that could drop as much as a foot of snow in the Sierra Nevada and several inches of rain in the valley and foothills. But because the last two weeks have been relatively dry, the storms shouldn’t flood low-lying communities as did storms in previous months, Bingaman said.


California is in the middle of its wettest year in decades and possibly its rainiest year on record. The state has been hit with more than 30 so-called atmospheric rivers, warm storms from the Pacific that carry massive amounts of rain that have saturated much of the state and built up the snowpack in the Sierra Nevada.

joseph.serna@latimes.com

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