By Lisa Baertlein and Ben Klayman

LOS ANGELES/CHICAGO (Reuters) - U.S. retailers' final weekend sales push before Christmas was under threat as a severe winter snowstorm struck the East Coast, forcing store closures and keeping shoppers at home on "Super Saturday."

The last Saturday before Christmas typically accounts for about $15 billion in retail sales, and analysts said the U.S. Northeast contributed around 30 percent of that amount.

It often vies with Black Friday, the day after U.S. Thanksgiving, as the biggest single sales day of the holiday season, and some analysts say a weak result could force retailers to slash prices in the run-up to December 25.

By Saturday evening, the storm blanketed the Baltimore-Washington area with snow and forced the closure of many stores and at least one area mall. It could bring blizzard conditions to other major shopping areas like New York and Boston. The National Weather Service warned of "extremely treacherous" travel conditions throughout the region stretching from the mid-Atlantic to the Northeast.

Only half of the stores in Taubman Centers Inc's <TCO.N> three Virginia malls were open because bad road conditions prevented staff from getting to work. One of those malls, in the Washington suburb of Fairfax, will close at least five hours early due to weather, said spokeswoman Karen Mac Donald.

"The one thing a retailer doesn't want is a major snowstorm on the Saturday before Christmas," said Marshal Cohen, chief industry analyst at the NPD Group.

"The weather this year is like Bernie Madoff last year. A terrible ending to a terrible year," said Shawn Kravetz, president of hedge fund Esplanade Capital. "The timing is brutal."

SHOVELS, SALT

Trend spotter Marian Salzman said she saw empty streets and parking lots as she checked stores at midday in Connecticut.

At a Wal-Mart <WMT.N> store in southwestern Connecticut, snow shovels and ice salt were in greater demand than holiday gifts, said Salzman, president of Euro RSCG Worldwide PR.

"Yesterday and today we did see increased demand for weather-related products like shovels and ice melt in our stores in the Northeast," said Walmart spokesman David Tovar, who declined to comment on specific sales data.

Analysts said the severe weather could depress sales on Saturday at retailers with a large presence in the Northeast, including Saks Inc <SKS.N>, Macy's Inc <M.N> and American Eagle Outfitters Inc <AEO.N>.

They expect some shoppers will venture to stores on Sunday, while others will settle in at home and shop online.