Retailers expecting to ring up sales in the days after Christmas may have to intensify discounts after a weekend snowstorm slammed the East Coast.

Parts of New York and New Jersey got as much as 2 feet of snow over the past few days, keeping many shoppers at home. Spending may shift into January, according to Marshal Cohen, chief industry analyst at NPD Group Inc., a research firm based in Port Washington, N.Y.

“It’s like throwing a party and nobody comes because the focus has gone from post-holiday shopping to post-holiday travel,” Cohen said in a telephone interview. “Look for sales to be repeated by retailers. They’re going to be more aggressive. They’ve got to throw another party.”

The day after Christmas is one of the five busiest shopping days of the year, and it may take retailers two weeks to capture sales lost Sunday, Cohen said. At the same time, shoppers may lose their enthusiasm as the holiday season wanes, he said.

Despite the weather, some shoppers soldiered on to get deals. Ten minutes before the store opened at 10 a.m. Monday, an employee at Bloomingdale’s flagship Manhattan store let 30 or so early-bird shoppers into a heated vestibule so they could warm up.

“It’s Christmas, so that means we’re shopping,” said Ed Hutlas, 68, an engineer from Dallas visiting the city for the holidays, who stood inside the vestibule with his son and granddaughter. Hutlas said his first purchase would be a new heavy winter coat for his granddaughter.

Home Depot Inc. and Lowe’s Cos. sold out of snow blowers, and shoppers bought more shovels and ice melt, said Craig Johnson, president of Customer Growth Partners. The storm also likely will give online sales “a slight bump” Sunday and Monday, said Johnson, whose retail consulting firm is based in New Canaan, Conn.

Consumers may temper their spending if the storm’s aftermath stalls shopping for several days and the frugality of New Year’s resolutions kicks in, said Michael Dart, the San Francisco-based head of private equity at the New York consulting firm Kurt Salmon Associates.

“You’re moving into an environment where the consumer is going to be pulling back,” Dart said. “Retailers don’t want to lose too many of those shopping days. If it’s just today, it’s not a big deal. But the longer the weather remains bad, it becomes problematic for retailers.”