We went Sunday and it was quite dreary/rainy. The crowds were still pretty big, but very manageable. We arrived at maybe 7:00-ish, used a FP for Mickey & Minnie and then went to ride the safari. We went straight from the there to Pandora, used the mobile app to order some food, ate and then went to NRJ for our fastpass ending at 9:00. It was still very crowded at this point and raining so we went to Flame Tree BBQ to wait out the weather and watch the backside of ROL. After it finished my hubby and daughter ran off to ride EE and I took my son to Triceratops Spin. We headed back to Pandora with what felt like a huge crowd of people for EMH. We left Pandora at 12:30 and the crowds had finally started to thin but there were more people than I expected that late.
Admittedly, I spend as little time at AK as possible because it's my least favorite park but I would call the crowds average. (By average I mean crowded, but not slammed) I think on a prettier evening/ afternoon it would be much more crowded.
Soooo long story short, I would expect fairly high crowds... especially if the weather is nice.