I've done 60-mile round-trip commutes year round before but sans the snow and ice. It was a good three and a half to four hours a day on the bike depending on equipment and exertion level. I've backed it down to the mimimal 50-mile RT for times sake.

I've heard that the Virginia/Maryland area has ice under the snow. In that case, you may need studded tires if the ice is persistent. Being from the south, I'm way out of my league and have only ridden in flurries and sleet but I would humbly recommend, based on the distance of your commute investing in a 'cross bike that can handle 35 mm tires. If you can get a disc-version, all the better. There are several nice 700c studded tire options in 35 mm sizes available from Peter White. I have a disc-cross bike now but with road-width rims. I can get away just fine with skinny tires since we don't get much frozen precipitation, but I will be testing out some larger tires later this winter.

Unless your MTB is a hard-tail, I wouldn't recommend trying to do that distance unless you don't mind spending 5+ hours a day on the bike. But if you've got the engine, go for it! Give it a try but build up your mileage slowly and watch for fatigue and be careful with lack of sleep. I've found the more my ride time goes up, the more I need to sleep at night, approaching nine hours if I've put 3+ hours on the bike.