Early discounts offered this month by chains seeking to extend this year's shorter holiday season saw a dip in the numbers lining up at stores across the country, according to consultants and analysts making spot checks on the ground.

"We've seen many merchants start their promotions pretty much right after the trick-or-treaters have gone to bed," said Lauren Bitar, head of retail consulting at analytics firm RetailNext.

Jennifer Yen pulls to shopping carts full of items at Wal-Mart Supercenter in Denver, Colorado.

Sales made prior to Thanksgiving and Black Friday could erode "the spike that we have seen in sales dollars historically," Bitar said.

The day after Thanksgiving has been America's biggest shopping day, and this year more than 165 million people are expected to take part over the weekend, according to the National Retail Federation (NRF).