For a few weeks, it looked like the U.S. consumer might have gone cold. December retail sales came in flat despite the usual holiday rush as spending across categories like apparel, furniture and restaurants all softened over the month, according to data compiled by the Commerce Department. Then came Winter Storm Fern. The last week of January brought the coldest end to the month since 1995 and the most snowfall in 60 years, according to the retail weather analytics firm Planalytics. Mall