I got caught out in a bit of that.
I was on Fort Friday a bit after noon time when I heard thunder coming. I decided not to continue on to the plane crash and hastily made my way back to N. Brother where there were dark clouds brewing. When I crossed through the summit area I got buffeted around by wind a good bit and just as I got below treeline the sky opened up with heavy rain, thunder, lightning and hail. It got so dark I was considering taking out my headlamp for a few minutes.
On my way home I heard new severe thunderstorm warnings coming over the radio every 5 minutes or so. Looks like I made it out just in time. I was afraid I was going to get caught out in the open on N. Brother when the lightning started.
I hiked Katahdin and the Coe/Brothers/Fort loop over Thursday and Friday. There were some badly eroded sections on the Brothers, which might have already been there. I didn't notice an unusual number of blowdowns.