While traveling down MD 121 yesterday just west of the road for Black Hills Park, Montgomery County, I saw an unusual raptor fly across the road. It passed in about 100 yards in front of us approximately 20' off of the ground and my first impression was buteo. It proceeded across a newly plowed cornfield toward the tree line offering us a rear view. The bird then banked and continued parallel to the road at a distance of about 50 yards. The bird was colored much like a junco, solid dark gray above and clear white below. The tale seemed short, reminding me of a black vulture in comparative dimension, was held pointed slightly down and fanned, and was a dark reddish brown from above. Flight was a number of flaps, and then soaring. We only saw the bird for between 10 and 15 seconds, and lost it behind a hillock as it continued to fly low. 
 
I know what I think this was, but as there are no state records, I was wondering if anyone could suggest something obvious that I am not thinking of?