Isn't the real problem when the TTF does not reflect the "bad news" TAF and is relied on to continue past LPSD?
Which, of course, is to hide the myth that the TTF is "good for 3 hours", when in reality it is only 'good' until the next one is issued - on the METAR cycle or if a SPECI is needed!
I agree scrubba. Hence my candid TAF vs TTF comment back in post #77. I have seen TTFs go from no fog to TTF SPECI fog here NOW - no FM period or BCMG!
Fog is a wily foe and I don't know if we are always capable of knowing what it will do in three hours...