I don’t know what you’re seeing. No model shows anything close to 9+ days of highs of 70+ at Atlanta to finish Dec. The largest # of days I can find for KATL is 6 days, which is on the 12Z GFS (12/24-29): 70, 73, 72, 70, 71, and 73. And as this shows, 2 of the 6 days on this barely make 70. So, getting 6 won’t be easy. Many including earlier GFS runs don’t have 70+ on 12/29 with the 5 of 12/24-28 more common for the most.
That being said, IF it were to actually occur, 6 days of 70+ within 12/20+ would obviously be a very impressive anomaly! How rare would that actually be? Extremely! It’s only occurred three times since 1878:
-2021 (warmest 75)
-2015 (warmest 77)
-1984 (warmest 74)