The tone is usually broadcast on the county EMA frequency - at least that's how I've seen it done in other counties. In your case, it would be 155.805 - could be CSQ, or there might be a PL. Give it a listen next Wednesday at noon and see.
I know I wouldn't necessarily be able to hear the sirens if the wind was howling and being 7 miles away from the closest siren and inside my house. It would be nice to know if the sirens are activated via listening to the freq they are activated on via a handheld or mobile radio.
The last three tornado warnings, the signal on my county's EMA channel has been my first alert to it. (Not by much, though. It's maybe a few seconds before the siren starts going, and a few more seconds before the county sets off all the fire tones.)