One neighbor had a weather radio app, and the NWS set off the sirens because rotation was detected "on the East side of downtown Frisco."
That's where I live.
We got to watch the rotation pass directly over our street. It was pretty loose, and broke up as it passed over us, but we did get a rare opportunity to look straight up at the first stage in the development of a tornado.
It is basically a cluster of storm clouds going around in a circle, as seen from below.
You generally don't get to see these thing develop, because they are wrapped in heavy rain. We got lucky.
Oh, and thanks Planovet for calling to check up on the dog.

CD