The HRRR has been quite consistent in developing scattered thunderstorms later on. Supercell is a far stretch but should see some strong storms I think.
I was thinking alot about that potential last night. I recall a very similar scenario last year (was it with Isaias?...it had to be) where there was alot of aggressiveness towards supercells and tornado potential and it did not materialize at all.
Both times featured (what you would think) pretty impressive llvl CAPE/shear...but nothing really came about it. Unfortunately these type of setups/events aren't very common so it's difficult to do hardcore research. But my thinking is when you have an airmass that is so capped with so much going on (convection, showers), it's very difficult for what develops to fully utilize the ingredients available. Yesterday though...the llvl shear may not have been strong enough yet to produce...that Danbury cell was close.
The window in these setups is small b/c what develops initially has a very short window before convection just blows up...and what happens is everything materializes into a widespread strataform rain shield. Perhaps a combination of too much strong isentropic lift and and not enough capping.