Above is a high resolution image of the San Antonio area radar taken just a moment ago (click to enlarge/clarify). I have circled, in white, 7 strong to severe thunderstorms - any one of which could produce a brief tornado at any given moment. Such will be the situation as we progress into the overnight hours...
Rather than having conditions favorable for isolated, relatively "long" track tornado potential (as we saw earlier this evening near San Antonio), storms with the type of configuration we'll be seeing overnight (such as those shown above) tend to produce relatively short lived tornadoes, which can be difficult to detect on radar.
In many ways, the situation tonight is very similar to the one in which a tornado touched down in northeast Austin and caused extensive damage over a relatively small area in late January of this year.
So, my advice for tonight would be that if severe weather threatens your area, go ahead and seek shelter as if a tornado were taking place, even if a specific tornado warning has not been issued. If you have a basement, go there. If you don't, seek shelter in a small, interior room on the lowest floor of your residence. By all means, stay away from windows.
Damaging wind gusts and large hail can also be expected with the activity overnight, as well as very heavy rainfall which will cause flash flooding in areas proned to such a threat.
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