I also like watching the HRRR every hour and see it produce these little unexpected convective bursts every now and then that don't appear in previous runs...
I bet Doug Heady jumps like this during big snowstorms too. I did the exact same thing last night, though.
https://www.facebook.com/MeteorologistDougHeady/videos/2470748913199639/
Not sure, and it's the NAM so I wouldn't worry about it. The exact track of everything is going to weeble-wobble from run to run. I wish it wasn't as narrow, but the system is positive tilted.