It'll cost some money, but I recommend that you get some dedicated winter tires for your trip! You can't put a price on your safety!

I just had some Bridgestone Blizzak's installed yesterday and it's a Night and Day difference in how the truck drives on snow! Well worth the money spent because now if my wife takes the X anywhere, I know that she's in good, capable hands! I Definitely wouldn't say that with the 20's on, but then again, it was safe for her to drive as long as she didn't leave the garage!

There were a couple of people on this forum that had gotten winter tire setups for their X5's and swayed me in that direction, so I'm trying to pass that on (Thanks for your posts PolePosition and King and C's Bimmer )!

I drove ours with the 20's on it in the snow and while it went forward alright, it didn't brake and slid all over the place in turns! As a matter of fact, I kept it in the garage until the winter package came in and just drove our other car! There's a good chance that you won't be able to get my butt out of the seat as far as driving in the snow since it's gotten it's new kicks!

Good Luck and Please Have a Safe trip!

Here's the video that they were talking about:

YouTube - Tire Rack Tire Test - All-Season vs. Winter Tires