Bread wasn't the only thing rising at Panera (PNRA) today: The stock rose at the open and quickly expanded its gains to 3.5% by 12:30 p.m. EDT. Analysts at Raymond James upgraded the stock from "underperform" to "market perform," marking the second positive move this week after Deutsche Bank analysts added the bakery chain to its short-term buy list on Monday.

Panera has done a good job of following the trend toward healthier eating options, with numerous reviews citing it as the healthiest option for fast food in America. Even as many restaurant chains have had to cut back on their menu offerings due to high input costs, Panera has expanded its menu, incorporating pasta in order to appeal to its high-end customer base. Even fellow health-focused chain Chipotle Mexican Grill (NYSE: CMG) hasn't been able to duplicate Panera's success in keeping a lid on its food expenses, as Panera's decision to keep bread-dough production in-house has produced big rewards. By maintaining an emphasis on premium quality, Panera is able to avoid the margin-destroying moves that weaker competitors have had to make.

In many ways, Panera has learned its lessons from coffeehouse giant Starbucks (SBUX 1.00%). Like Starbucks, Panera has worked hard to make its restaurants inviting with Wi-Fi service and a comfortable setting encouraging customers to treat each Panera location as a second home. Panera has also reached out to the communities it serves with initiatives like the Panera Cares pay-what-you-can locations for needy people seeking food.

What's really supporting Panera's stock?
As easy as it is to point to analyst upgrades as a reason for prices to make short-term moves, Panera's success over the long run depends on two key factors: its ability to keep giving its customers the products and dining experience they want and customers' willingness and capacity to keep rewarding a much-loved restaurant chain with their business. Positive signs on both fronts have been evident for a while now: Growing same-store sales, more productive per-store weekly sales, and ambitious expansion plans all point to favorable prospects for Panera. As long as the company keeps seeing such good results, today's pop in Panera stock will be just the tip of the iceberg for long-term investors.