Originally Posted by
32LatT10
I have seen this before where the block time was extended a bit a few months out. This was a TATL flight in December if I recall correctly. I surmised they updated it once they had a better sense of seasonal weather patterns. I wouldn't think they would want to unnecessarily pad block times too much (despite improving on time performance metrics) because it impacts connections and where flights appear in search results, etc.
Seasonal wind as input to flight times is based on long-term average historical records, not predicted activity. There's not enough skill in the latter for it to be of use.