I had a difficult one to judge day before yesterday:
I was flying into Naples LIRN, coming from the NE, scanning with the Radar. From ontop there were no huge CBs, as far as I could see, just what I assume to be the mountains depicted on the radar. getting in coser (the ILS starts at 7000', A/D elev ca 300') I reduced my range, and got a huge red one right on the ILS. Somehow I didn't believe it, there was nothing indicating big TS before. I have seen Radars overdraw at close range, so I told the FO to keep on flying. He was twitching a bit in his seat, but I asked him again and again if he was still ok with the situation, or if he wanted to goaround (wich would have taken us the same way, and it would not have been smart to take a turn off the ILS, because of the high MSAs around us.
The radar indication was a clear "do not go there", but the assesment of the situation before the approach said "it's ok".
I really wasn't sure what to do - high terrain, red blob on the radar ahead, in clouds! As we didn't get hit any harder than heavy rain, I decided to continue, and so did the FO...
There was no severe Turbulence, no hail, just a lot of rain, and an uneventful landing.
Either we just got lucky, or the assesment from high altitude proved to be right (I lean towards that one) - but on an approach to another airport with easier terrain, I would have broken off, to reevaluate...
Nic