The National Climatic Data Center released an interactive map showing the historical probability of a white Christmas for the lower 48 states:
Are You Dreaming of a White Christmas?
Using the interactive map, the highest percentages I could find in Ohio are in Geauga and Ashtabula County (Chardon is at 61%) and the lowest are in the very southern tip of the state, Scioto, Lawrence and Gallia Counties (Gallipolis was the lowest at 3%).
In Pennsylvania, the highest percentages are in the snowbelt south and east of Erie (Kane is 74% and Union City is 72%), but also Wayne County northeast of Scranton (Pleasant Mount is 71%) and in the highlands around Somerset and Johnstown (58%).
The lowest probability of a white Christmas in Pennsylvania is in Marcus Hook, at the extreme southeast corner of the state, at just a 1% chance of at least 1 inch of snow on the ground on December 25th.