It's quite common that   mighty  is used informally as very:   mighty hot weather,  mighty fine cooking,  even,  mighty tiny  computer chips.   But I've never heard   powerfully  like that,  like in this on page 150 of Go Set a Watchman:
Can I take you to town, Mr. Finch? Â It's powerfully early, but I think I'll run down and tend to some things in the cool of the morning
Something tells me that's how it's used   all the times  in those parts,  but only in those parts.  Â
Is that usage familiar to you?
Once again, I wish there was a Google n-grams viewer for casual spoken language. If you look only at the written word, especially the edited written word, that's a distortion of what ordinary languiage is.
I suspect that in ordinary informal oral English, you'd find that powerful is more common than powerfully, despite being illiterate in Miss Grundy's estimation. It's powerful fine expressive language.
I think deaconB is right about powerful being more common but I have heard powerfully used like that many times. Another colloquialism that I like is right. As in,"This is a right nice day." Or, "I feel right fine today."
Dick said
I think deaconB is right about powerful being more common but I have heard powerfully used like that many times. Another colloquialism that I like is right. As in,"This is a right nice day." Or, "I feel right fine today."
In Just That Much Hillbilly in Me, a 40-minute long video, there is a section where a fellow is talking about right smart. I did not take the time to try to find it. Maybe one of you who does can note the timing for others reading this thread.
It's right smart? Not rat smart? Dagnabbit. time to wash the wax out of my ears!