December is here, the time when Robert Pannuto gives his yearly snowfall prediction, and the Marshfield weather expert is warning, “Get your snow blowers and shovels ready.” He predicts a 65 percent chance this winter’s snowfall will be above the average of 42 inches. Pannuto, a retired meteorologist for the National Weather Service at Boston and an assistant professor at Bridgewater State University, has his own system, basing his snowfall predictions on October and November temperatures. Warmer than average temperatures precede less snowy winters; lower temperatures indicate more snow. Last winter, Pannuto’s system held true. After a fairly toasty October and November, winter yielded only 9.3 inches in the Boston area. This year, however, is a little trickier to interpret, said Pannuto, since October was warmer than average but November was colder. He’s basing his prediction on the later month and therefore expects a snowy winter.