What if you don't have the TTF? We will have to wait and see what the time line shows but there is no requirement to update TTF's if you departed with a valid TAF. If the crew considered that the safer option was to continue to ADL (if it had CAT III) rather than to divert to an airport OCTA and that they were unfamiliar with then they would be ok
Reality is you would be given the update through ATC so even if you didn't go looking for it you would end up with a new TAF. As soon as that happens you would have to do some recalculations.
There is also a requirement to have the most current TAF on you if you can't get or use the TTF.