Melbourne Grand Prix day 2019. MEL TAF screams fog in all but the letters "FG" from at least 18 hours before.
Depart LAX for MEL with usual reserves plus a top-up to MTOW but not enough for a planned alternate other than ability to go to AVL.
4 or 5 hours out of MEL every aviator reading the MEL TAF or TTF except the BoM TAF and TTF writer knows MEL is about to fog in.
70nm abeam SYD TTF released "MEL 400m FG"….unfortunately AVL was also below Alt Minima and would probably be worse by the time we got there.
Divert to SYD via well south of CBR and landed in arguably even worse weather in Sydney - vis 2000m in pouring rain and a strong, gusty south-westerly. F/O did a great job!
A couple of hundred pax didn't make the GP as all the domestic flights were full and not enough standby A380 cabin crew in SYD so our jet went empty to MEL - but that's another story.
It often amused me that the BoM operators could be incredibly conservative in forecasting non-critical weather (eg: INTER 5000m in RASH when there'll likely not be a cloud in the sky) but then be reluctant to forecast critical weather like fog and thunderstorms.