Which group of information in a TAF supersedes all previously forecast weather?

The "From" (FM) group in a TAF (Terminal Aerodrome Forecast) represents a significant forecast change that indicates a new weather condition will begin at the specified time. This group supersedes all previous forecast weather information because it marks a clear transition to a different weather scenario that is expected to take place. When the FM group is issued, it essentially establishes a definitive weather state that takes precedence over earlier portions of the TAF.

In contrast, the other groups serve different purposes. The "Temporary" (TEMPO) group is used for short-term weather fluctuations that are expected to last for a limited duration and do not replace the overall forecast but rather provide additional details. The "Becoming" (BECMG) group indicates a gradual change in conditions over a period of time, rather than an immediate shift. Lastly, the "Probability" (PROB) group is often a contingency forecast that indicates the likelihood of specific weather occurrences, but it does not provide a definitive forecast like the FM group does.

Thus, the FM group is the clear choice as it denotes a change in the forecast that overrides all previous weather predictions contained in the TAF.