"But it still requires that certain atmospheric conditions are present, all of which can be forecast."
I am glad you said "can".
It is very common along the south coast - my pet theory is it is getting commoner.
It is often forecast - rarely very accurately in terms of time or duration - and often forecast just before or even after it has occurred.
I do agree however no particulay good reason to be caught out by it though as you can see the wall of fog from some distance and are already likely to be above it. If you happened to be routing along the coast I suppose it might well "blow in" around you if you were relatively low level. IMO this would be another very good example of the right occasion to climb above - totally safe because you know it is only a few thousand feet at most, and the weather will remain as predicted north in shore.