I think this may be an "Audubon's" Warbler--- one of the two races of Yellow-rumped Warbler. It is the more western race, and is probably a future "split" by the AOU. Recent studies suggest that Audubon's has different dietary needs, along with known differences in vocalizations. The observation is significant in MN, where Audubon's is likely casual in occurance. It would be worth reporting on the MOU website, and posting your photo there as well.
Thanks for sharing the photo!
Drew Smith, Eagan MN