Yep, the cold stays hoverin' with us, the sun shines for perfect riding, and South finally opened for the civilians (season passholders got to ride it first). Hey, we're there on 26 trails and the snowmakers' eyes are glazed over as they keep those guns roaring. And this... if you're near The City Thursday, head over to Union Square for NYC's first pro-snowboarding event, giving props to some of the urban origins of riding. Things start at 3 p.m. and go through 8:30 p.m. Looking for Hidden Valley doings? How about a skier- boardercross event on Saturday.