high temp overshoot

Freaky Deaky... Okay, novice smoker here, never had this happen to me and I hope those w/more experience can shed some light on the whys and wherefores... Smoking an 8 lb butt, picnic, 7 lbs. after trimming, set on the bottom rack of my 14.5" WSM. There's a rack of pork spare ribs cut in two...