Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0745 PM CDT Tue Apr 21 2026 Valid 220100Z - 221200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE SAN JOAQUIN VALLEY OF CENTRAL CALIFORNIA... ...SUMMARY... Isolated strong thunderstorms are possible in the San Joaquin Valley of central California early this evening, capable of isolated severe gusts and perhaps a tornado. ...San Joaquin Valley... Latest water vapor imagery shows an upper-level low just off the coast of far northern California. A mid-level jet is wrapped around the southern edge of the system. Within the left exit region of the mid-level jet, a couple of strong to severe thunderstorms are ongoing in the San Joaquin Valley. Strong lift is present along the northern gradient of the mid-level jet, which is coincident with a pocket of instability, with the RAP showing MLCAPE in the 250 to 500 J/kg range. Over this area, the mid-level jet is creating deep-layer shear exceeding 85 knots. This environment will continue support a marginal severe threat. Isolated severe wind gusts and perhaps a tornado will be possible for another hour this evening. ..Broyles.. 04/22/2026Read more