Not even a snowstorm could keep the girls away from “Mad Men” star Jon Hamm at the Diesel after-party for his new movie, “Howl,” at Sundance. “They were so eager to get their photo taken with him that they knocked one guy to the ground,” a spy reports. Unfortunately for his admirers, while Hamm did pose for photos, he was with girlfriend Jennifer Westfeldt. “Howl” star James Franco was also at the party.