Offshore wind farms are normally lighted with high intensity beacon as per aviation regulations. Even in poor weather they are clearly visible when flying.
Unless of course the cloud base is below the nacelle - but such weather can't really be called VMC.
In regards of the radar signatures, they should be easy to filter out since the wind turbines aren'r really moving anywhere.
Personally I think it makes much more sense placing them out to sea than on land. They are more efficient and don't disturb the neighbours.
Well, just my thoughts.
RD