Only three QNH's are given on a 12 hr TAF. One for now, four hrs in, 8 hrs in.
Incorrect. Chimbu is right in the first place.
Jepp Met 11.16.3 Up to four (4) forecast values of QNH are given, valid at three (3) hourly intervals commencing at the beginning of the validity periods of the forecast.
Where I fly, 99% of the TAF's are valid for 12 hours. We always get four QNH's and Temperatures for the reason above. You will also find that area QNH's on an area forecasts are also only valid for three hours.
