Tire + pothole = flat tire
 

So I had a flat tire lastnight(second flat this winter) and I'm guessing its from a pot hole. My question is how does it happen? Does the pot hole push the air out of the valve stem, (I had no cover on it) or does it put a small to large hole/cut in the tire?

Most pothole flats are the result of too little air in the tire allowing the impact to tear the rubber and break the belt inside the tire. It can also bend the rim and let the air out there. Did you locate the leak point?

It can break the bead loose from the rim if you hit hard enough.

I haven't really looked for where the leak is And it had 35 psi in the tire, also the rim doesn't look bent.