The utility of a stormscope (I have the WX500 too, driving a KMD550 MFD) for avoidance of hazardous wx while flying in IMC is limited.
It should stop you flying into something that is going to take your wings off, because the biggest updraughts are claimed to generate the most strikes, but anything below that level of turbulence is pretty variable in its electrical visibility.
If I was in IMC and totally stuffed, with TS activity around, I would use the scope to get out of there, but it's not good enough for routine use enroute.
Wot you need is a plane with a decent operating ceiling to do the enroute section in VMC, which means oxygen or pressurisation
and some web resources to estimate the cloud tops before you go flying.
Also, speaking of a "cloud" with a top at 13k, that was probably a reasonably mean CU/TCU and one can get quite adequately shook up inside one of those, anywhere. You need to play a long game enroute and avoid all that stuff.
It is also quite feasible for a buildup to go "electrical" quite suddenly. A friend of mine was flying along (in IMC
) and reportedly within a few seconds the whole scope lit up like a xmas tree - all around him. A few seconds later he was in severe turbulence.