Don't look for a hard and fast opening date at Mad River Glen, as this one-of-a-kind area relies on natural snowfall to cover its trails, but the plan is to open as soon as possible and at the latest to be up and running by Dec. 15. Mad River's Eric Friedman said the area hopes to open around Thanksgiving, which is the traditional start of the New England ski season, but that the date is entirely weather dependent. The dedication of the "new" single chair will occur Dec. 15, he said, snow or no. Many Mad River die-hards already are skiing on snow that has fallen heavily there and elsewhere across the higher elevations of Northern New England.