Definitely if you are flying from Minneapolis in December you want to plan on coming in the day before. I was going to say that you would be fine arriving at 1PM but in December there most definitely could be weather delays. You will be much more relaxed on your first day of the cruise if you don't spend them whole morning worrying if you will make it on time.
We seem to sing the party line around here of getting in a day early. The is the best option. But we also understand that it is not always possible nor affordable (however, many times it makes the flight cost lower and compensates some for the extra hotel cost). Also understand that a majority of cruiser arrive on the day of the cruise. This may be a fine option (and we have done it a couple of times) for summer travel, but it is just too risky in the winter.
Carnival Cruise Lines:
Fantasy 90, Celebration 95, Victory 05, Conquest 05, Spirit 6/06, Freedom 6/08, Holiday 7/08, Victory 6/09, Valor 9/09, Dream 6/10, Splendor 8/10,Conquest 8/11,Magic 11/11,Triumph 4/12,Spirit 7/12,Freedom 11/12, Triumph 2/13 - The fire cruise
NCL Dream October 2006, RCCL Mariner OTS June 2007