CaT - I believe Stockton area had a tornado on Wednesday that touched ground. As I recall the first in 7 years or so for the area (possibly the entire county, but I don't recall all of the details).
Here is the report for that event from the Storm Prediction Center's website for Wednesday.
4 W FRENCH CAMP Tornado Report
County, State: SAN JOAQUIN, CA
(marker location is approximate)
Lat.: 37.88, Lon.: -121.34
Time: 2012-04-11 20:00 UTC
PRELIMINARY STORM SURVEY REVEALS AN EF1 TORNADO OCCURED NEAR THE INTERSECTION OF HOWARD ROAD AND SOUTH ROBERTS ROAD
"4 W" = 4 miles west of". "EF1" is the Enhanced Fujita scale of tornado strength based largely confirmed damage reports after the fact. The scale ranges from EF0 to EF5, with EF0 being the weakest.
CaT