IIRC, I read once that drunk people are less likely to be injured in car wrecks than their sober counterparts, and that when they are injured, their injuries are often less severe than those of sober people. The explanation behind this was that drunks' minds and bodies both have delayed reaction times, and their bodies are therefore often "limp" at the critical point of the wreck, which allows their bodies to better absorb the impacts (thus minimizing the damage.) If there's any truth to that, then getting sh!tfaced could actually increase your chances of surviving a tornado...
I'm guessing the actual sheltering area might be the big ol' beer cooler, in back. More than once, walk-in freezers/coolers, and bank vaults, have been the only things that survived a large storm.