Tony Perkins and David Drufke and myself headed to Sioux City, IA around 10:30am. We took the Saturn Cruiser, good ride, decent ride and not horrible gas mileage. I took the scenic route through IA versus a more direct route stopping to take some photos along the way. Passed though a huge wind farm, not only were they growing corn everywhere but, they were generating kilowatts of energy. Aside the road we passed a large stack of propellers(20?), seeing them up close they are huge. We were around Cherokee, IA as MD756 was issued at 3:28pm and continued on towards the warm front. We stopped in Hinton, IA and began heading North East right around the time Tornado Watch 243 was issued(4:35pm). Two cells had popped up just over the border in NE soon to be crossing into SD near Springfield, SD. We continued N/NE as we had expected more cells to form along the boundry. Around 5:30pm we had stopped for some time looking at some nice crispy looking fresh updrafts (one after another) but, just not becomming organized. We were still expecting the line to build Eastward into better conditions, higher instabillity, and better moisture as we made our way North. Eventually blasted to intercept the nearest tornado warned cell in SD. MD759 was issued at 6:36PM. We caught up to a large cell South of Parker, SD at 7pm as the Rock Valley F2 tornado set down further down the line into IA as we had expected. The Rock Valley tornado travelled 13 miles over a 25 minute period, the tornado was estimated to be up to a quarter mile wide but, missed that one. We followed the Parker cell and watched some rapid motion at various times but, nothing highly organzied. MD762 was issued at 8:02PM followed by MD763 at 8:28PM pointing out the continued hail risk/possible Severe Thunderstorm Watch from near Sioux Falls, SD to the Twin Cities. Photo to follow..