A snowstorm which arrived early this morning dumped up to 10 inches of white stuff on parts of the Pocono Mountains and left 47,000 PP&L customers in Northeastern Pennsylvania without power. What began as rain accompanied by thunder and lightning in the Carbon and Schuylkill area, developed into the first major snowstorm of 1977 with accumulations of three to five inches reported in the Panther Valley-Tamaqua vicinity.