For most of New Jersey, the big December storm that pelted the region from early Sunday through Monday morning brought a few inches of rain. But in some parts of the state, cold air swept in at the tail end of the storm, turning the rain into the biggest snowfall of the season. As much as 5 inches of snow fell in High Point State Park in Sussex County — the state’s highest elevation — in a few hours Monday morning, according to the National Weather Service. Almost 2 inches of snow coated the ground in the Green Pond area of Morris County, and almost 1 inch of snow was measured in Holland Towns…