As shoppers unwind from the holiday season, investors are gearing up for key reports about how retailers fared. Most chain-store sales figures for December will be released Thursday, and the numbers will shed light on which retailers scored during the holiday shopping season and which ones came up short. Analysts are weighing the impact of unseasonably warm weather, severe markdowns on electronics, and savvy shoppers who held out for late-season sales. "I think we're going to see a fairly dispersed performance curve among retailers," says Michael Appel, a restructuring specialist with Quest Turnaround Advisors. "The keys will be what kind of markdowns they took pre-Christmas in order to make their sales plan and what post-Christmas markdowns they have to take to clear out seasonal inventories." According to Thomson Financial, analysts expect an average 3% rise in same-store sales for December, below the 3.3% sales gain from a year earlier. But if Wal-Mart ( WMT) is removed from the picture, December sales are on track to increase to 4.6%, besting the comparable year-ago gain of 4.1%. Wal-Mart said over the weekend that same store-sales at U.S. stores rose 1.6% during the five weeks ended Dec. 29 from a year earlier. That was better than the company's forecast for an increase of no more than 1%. It also represents a rebound from a 0.1% same-stores sales decline for November.