Best Buy Co. Inc. forecast fourth-quarter comparable sales below analysts’ estimates on Tuesday, as the electronics retailer braces for a hit from likely product shortages during the crucial holiday shopping season. The company’s shares, which have gained nearly 40 percent this year, fell 11.2 percent to $122.55 in premarket trading. Retailers are under tremendous pressure to keep shelves stocked for the holiday season as shipping logjams, shuttered factories in Asia, and a scarcity of raw materials rip through global supply chains. A shortage of semiconductor chips used in electronic items has dented the availability of some high-demand products, including the latest gaming consoles from Sony Corp. and Microsoft Corp. Some analysts have also warned that supplies of Apple Inc.’s latest iPhones could take a hit during the holiday season. IPhones and new gaming consoles are hugely important for Best Buy as they not only sell in large numbers, but also …