I actually flew back from Crete into Manchester about 2 hours before THE storm hit later in the day Tuesday. There were enormous cumulonimbus the length of Italy, and we skirted past at 36000ft of one around Venice, possibly a little further North (Just inland from the Adriatic sea) We did a right turn to avoid going over the top, then a left turn to continue towards the UK via France, however we had not a drop of turbulence the entire flight. Incredibly smooth the whole way. I was amazed.