Dunlop SP Winter Sports (either M2 or M3s).........one of the few high performance winter tires recommended by Porsche.....think of these as the winter/snow equivalent of the stock STi tires.
Good performance in snow/slush/dry conditions when temp drops below about 40F (check out reviews at
www.tirerack.com). Irregardless of whether you live in the snowbelt you really should swop-out the stock STi tires if the winter temps were you live are frequently below 40F......
Have run 225/40s on 18" rims over the past several years (and it snows here a lot) and they work like a charm.