I'd just watch the weather reports and plan to sit for 24 hours if I-81 gets hit by snow. VA and PA do a pretty good job of clearing roads, you won't have long to wait. it would be my choice to wait rather than try to drive I-95 with its traffic and tolls.
"I usually take I 81 down to I 77 and cross over to I 95." I think you're going out of your way if traveling Florida to Massachusetts. I-77 runs from Cleveland, OH to Charleston, WV, Charlotte NC and then south.
From MA I use I-84 to Scranton, PA then S on I-81 to Middletown VA and I-66 to Exit 26 then US 17 until in joins I-95 S of Washington, DC. You avoid all major traffic and tolls, and the stretch of I-81 isn't too bad except for Harrisburg, PA. All the states your traveling through also have websites on highway conditions so you can know before you take off each day what you're going to encounter.
Bob & Donna
'98 Gulf Stream Sun Voyager DP being pushed by a '00 Beetle TDI