Oil prices firmed near $52 a barrel on Monday as a blast of cold, snowy weather in the U.S. Northeast threatened to tighten already strained heating oil supplies in the world's largest energy consumer. U.S. light crude futures CLc1 rose 26 cents to $51.75 a barrel on the New York Mercantile Exchange after striking a fresh four-month high of $52.28 in open-call trade. London's Brent crude LCOc1 rose 35 cents to $50.06 a barrel on the International Petroleum Exchange. U.S. demand for heating oil was expected to rise about 14 percent above normal this week as a major winter storm ran the length of the East Coast, leaving snow and frosty temperatures in its wake, according to the U.S. National Weather Service. U.S. inventories of heating oil are already running more than 7 percent below year-ago, even as the stockpiles of gasoline and crude swell more than 8 percent percent higher than last year, according to government figures.