d = {str(row.getValue("Column1")): (str(row.getValue("Column2")), str(row.getValue("Column3")), str(row.getValue("Column4"))) for i in arcpy.SearchCursor(xls,"[Column1] = 'Lake_Huron'")}
OR
d = {str(row.getValue("Column1")): (str(row.getValue("Column{0}".format(i)) for i in [2, 3, 4]) for i in arcpy.SearchCursor(xls,"[Column1] = 'Lake_Huron'")}