U.S. retailers might have lost $1-billion in post-Christmas sales due to the massive blizzard that struck the Northeast over the weekend, according to a report from ShopperTrak, the retail sales analysis firm.

Total foot traffic on December 26 (the day the snows first fell) was 11.2 percent below what it would have been expected if the blizzard hadn’t pounded the east coast, ShopperTrak estimated. On December 27 (the first day of the work-week in which many roads remained impassable and people had to contend with more than two feet of snow) total U.S. foot traffic was 13.9 percent below expectations had the blizzard not hit the Northeast.

Foot traffic in the Northwest fell a brutal 42.9 percent compared to 2009, while other regions of the country actually recorded a gain.

The 2010 blizzard throughout the Northeast halted nearly all retail visits and spending during a period that is fairly crucial for retailers, ShopperTrak founder Bill Martin, said.

Considering that retail sales estimates for December 26 and 27 were about $10 billion, ShopperTrak assumed a 10 percent negative national sales impact from the blizzard, resulting in the $1-billion loss estimate.

“And at this point the prospect of momentarily pausing a potential $1 billion in sales has the collective industry holding its breath, Martin said.

While we do think there will be some retail strength later this week 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.”