NEW YORK/CHICAGO, Dec 18 (Reuters) - U.S. retailers opened their doors on Saturday to what they hope will be swarms of shoppers searching for last-minute holiday gifts, despite surging cases of the coronavirus, including the new, highly-contagious Omicron variant. The last Saturday before Christmas – dubbed "Super Saturday" – is typically one of the busiest shopping days of the year, marked by a rush to buy last-minutes gifts to tuck under the Christmas tree. The risks to shoppers this year, however, are not just that merchandise might be out of stock, but also that in-person shopping could trigger more coronavirus infections - making Super Saturday a super-spreader event. Toy store owner Katherine Nguyen says she anticipates more people to shop in person at her three Chicago-area locations compared to the last Saturday before Christmas 2020, or even the last Saturday before the pre-pandemic Christmas of 2019. "It"s like the new variant is the new normal – the environment has gotten a little used to that," she said. Foot-traffic tracking firm Placer.ai said it expects more people to visit stores this weekend than on the same weekend last year. Sensormatic Solutions, a data firm that measures store visits, cited a nearly 48% increase in foot traffic on the Friday after Thanksgiving compared to a year earlier as a sign that people would want to shop in-person. A supply chain logjam has left many people also feeling nervous about not getting merchandise ordered online in time for the Dec. 25 holiday. "Consumers have been bombarded with messages about the impact of supply shortages on the availability of holiday gifts," said David Berson, chief economist at Nationwide in Columbus, Ohio. Nguyen said her three stores never received shipments of merchandise for about 15% of their toy catalog. The toys, she says, are "sitting on a container in Long Beach, California, outside of the water waiting to come in." FedEx (FDX.N) and the U.S. Postal Service set Dec. 15 as the deadline for ground deliveries to reach homes in time for Christmas, which means that shoppers still in search of gifts may have little choice but to shop in stores if they want to avoid fees for expedited shipping. FedEx and rival United Parcel Service (UPS.N) each say they have hired enough workers to manage the holiday peak, when the number of daily packages they handle easily doubles. Unlike last year, many consumers heeded advice from retailers to shop early - easing pressure on carriers by spreading demand over a longer period of time. But online shoppers may see more delays as Christmas approaches, according to Cathy Morrow Roberson, president of consultancy Logistics Trends & Insights. Reporting by Arriana McLymore in New York and Richa Nadu in Chicago, and Lisa Baertlein in Los Angeles. Additional reporting by Siddharth Cavale. Editing by Rosalba O"Brien Our Standards: The Thomson Reuters Trust Principles.