PROVIDENCE, R.I. — A weekend storm bearing down on the Northeast on the first day of spring is expected to dump up to a foot of snow on some parts of New England, making for a very messy Monday morning commute, but could leave behind only a couple of inches and clear skies in some mid-Atlantic cities. In southern New England, forecasters are predicting heavy, wet snow and accumulation of 6 to 8 inches in Massachusetts and Rhode Island, said Stephanie Dunten, a meteorologist with the National Weather Service in Taunton, Massachusetts.