Stock summer tires in light snow ?
 

I'm taking my S5 from Phoenix to Yosemite this weekend. Looks like there'll be light snow (2 - 3 inches) while I am there. I'm currently riding on stock continental summer tires. Do you think I can get away with it if I drive slow and leave plenty of space? I used to live in PA and I'd have snow tires on my car for winter, so I know the importance of tires. Has anyone with the stock summer tires driven in any light snow? If so, how do they perform?

They perform like crap. You'll still get going but good luck turning and stopping.

Do a search on "glass transition," the temperature where a summer performance tire's grip/slip performance changes dramatically. This means the summer performance tires that provide predictable traction in warm to hot conditions will be found to be very challenging to drive in cold to freezing temperatures. They can also get micro cracks and end up in the dumpster.

I took my stock contis to Brian Head Utah in light snow conditions last spring, they were not great at all. Be careful and don't expect the Quattro to save you with them. Stopping / steering can be crappy. I made it fine, but next time I'm going to the occasional snow I'm running cables on the tires.

No. No. No, and if I haven't made my self clear, definitely NO.

Seriously, summer tires have almost NO traction on snow, no matter how light. Aside from the rubber compound that turns hockey puck rock hard at cold temps, the tread pattern on a summer tire has no bite at all. You will spin your tires trying on anything but flat level ground, you will have no steering response and your stopping distances will be determined only by how far out in front of you the object you will hit is. I once made this exact mistake in a previous S4 when I got caught out in an unexpected early season snow. I honestly don't know how I made it home in one piece but it left a lasting impression on me. Never drive summer tires in the snow.

Don't risk wrecking your car, let alone your personal safety.

This video probably answered my question.

Wasn't their a post about a guy who drove with summer tires in light snow and slid into a curb and totaled his one day old Audi?

I'm probably going to drive a different car with all-season. It's a bummer I don't have a set of winter tires to put on the S5... My S5 has never seen rain let alone snow.

Make sure the tread on the A/S tires is at minimum 5/32 inches.

I plan on using winter tires in the winter, but how should I store my summer tires to avoid micro cracks? Never heard of this before...