A blizzard in the Northeast this weekend postponed about $1 billion in holiday retail sales by keeping shoppers out of stores in the days after Christmas, research firm ShopperTrak said on Wednesday.

The snowstorm shut roads and canceled flights in New York City and created havoc across the Northeast, where shopper traffic was 11.2 percent below ShopperTrak's expectations for Sunday December 26 and off 13.9 percent on Monday December 27.

The firm said sales for the entire November and December holiday period are on track to be up 4 percent, helped by strong sales in November and December 23, a particularly heavy day for shopping before Christmas.

It expects consumers who stayed home because of the snowstorm will venture out and shop more in the coming days.

While we do think there will be some retail strength later this week and into the weekend as folks begin to dig out, it will be interesting to see if levels recover in time to boost December sales and the overall holiday shopping season, ShopperTrak co-founder Bill Martin said in a statement.

Other analysts agreed that the blizzard, which dropped 20 inches of snow on Central Park in New York City and more in suburban areas, should only put a small dent into holiday season.

International Council of Shopping Centers chief economist Michael Niemira told Reuters the snowstorm could lower the December sales growth rate by 0.5 percentage point, though some purchases may show up in January.

Scott Bernhardt, the chief operating officer of Planalytics, put the hit at 0.25 percentage point, saying that people will eventually go to malls to redeem gift cards and exchange gifts, which they normally do on December 26 and the following days.

While the gift cards themselves don't generate new sales, customers often end up buying more items when they redeem gift cards or exchange gifts they didn't like.

Shares tracked by the Standard & Poor's Retail Index rose 0.4 percent on Wednesday, slightly better than a 0.3 percent increase for the wider stock market. The retail index is trading close to a 3-1/2 year high reached earlier in December on hopes a strong holiday season will add momentum to consumer spending into 2011 and propel an economic recovery.

Most analysts and research firms are expecting holiday retail sales to improve from 2009's sales.

The National Retail Federation sees holiday sales up 3.3 percent, compared with a 0.4 percent increase last year and a 3.9 percent fall in 2008 due to the financial crisis.

Online sales were up 13 percent to a record $30.8 billion for the November 1 to December 26 holiday period, data company comScore said later on Wednesday.

SALES OFF BEFORE BLIZZARD

U.S. retail sales fell 4.1 percent in the week ending on Christmas Day, according to ShopperTrak, largely because December 26 fell on a Sunday this year and was not included in the week's sales.

December 26 was the third biggest shopping day a year ago. The day could be as low as 10th in sales this year, ShopperTrak said.

ShopperTrak said that the start of inclement weather in the Midwest, Northeast and South regions likely lowered spending for the week too.

ShopperTrak noted that December 23 was the season's biggest shopping day after Black Friday, the day after the U.S. Thanksgiving holiday in November and the unofficial beginning of the holiday spending rush.

Americans spent $7.86 billion on December 23, while Black Friday accounted for $10.69 billion in sales, ShopperTrak said.

(Reporting by Jon Lentz and Phil Wahba. Editing by Robert MacMillan, Derek Caney and Bernard Orr)

Christmas Blizzard