The downpours/storms are very localised.
At the 24hr Le Mans yesterday afternoon a sudden downpour localised on one small section of the track had cars spinnining all over the place.
Meanwhile further west where I was flying the visibility was super although there were convective clouds rising fast. The glider pilots loved it. Bit bumpy in patches between 1500’ and 2000’ especially in the ULM. It (le pompe) would suddenly make the a/c roll left and rise and then it would be smooth for a while.
Yesterday two hours after landing at Liverpool in absolute CAVOK.
It gets more interesting if you are crossing the Alps, with the tops in front of you, around your level, a wide wall of them, and rising at about 50fpm, at FL160, ISA+10 
Nice one just after departure this morning… as a friend replied, if nothing goes right, go left
