>No place for Heroics in present day
It's all about statistics and eventually the really unusual cases will crop up - if there is a 1% chance of unexpected weather at an aerodrome - and there is a 1% chance of bad weather at the alternate. Eventually you end up with 0.01% chance of both destination and alternate being unsuitable. (yes the maths probably isn't correct if there is a correlation in the weather)
At some point you've got to pick the least bad option and make the best of it. (or come up with better alternatives on the fly.)