I looked to 2000, has happened a few times. Most recently in 2011, April 4.. 43/86.
Dulles actually has 5 above 50 but not that shocking for its location I suppose.
4/11/1977 87 33 54
4/3/1981 86 34 52
1/28/1987 35 -17 52
3/23/1994 83 32 51
4/18/1985 84 34 50