Although we don't believe in timing the market or panicking over daily movements, we do like to keep an eye on market changes -- just in case they're material to our investing thesis.

Six in 10 stocks ended in the black Tuesday, as markets began a shortened week of trading posting cautious gains. There wasn't much new data for investors today, and -- with the notable exception of companies reporting quarterly earnings -- this week looks to be light on economic news. For those living and working nearby Wall Street this week, bundle up! The National Weather Service issued a winter storm warning for New York City this afternoon, with estimates calling for as much as a foot of snow. The Dow Jones Industrial Average (^DJI 0.69%), in contrast with the other two major U.S. indices, lost ground today, shedding 44 points, or 0.3%, to end at 16,414.

Home Depot (HD 0.86%) shares didn't help the blue chip index Tuesday, shedding 0.7% as the services sector sold off slightly. While the weather may be cooling down, Home Depot's intense rivalry with its direct competitor Lowe's is heating up. Last week Lowe's made an interesting play, partnering with start-up Porch.com, a Seattle-based business that aims to connect consumers with contractors for various home-improvement projects. Although the upside is probably greater for Porch.com than Lowe's, you can bet that Home Depot's top brass will be keeping a close eye on how last week's move plays out. 

Bucking the bearish trend in the services sector today, Delta Air Lines (DAL 0.43%) stock soared 3.3% after fourth-quarter results topped Wall Street expectations. The company, technically speaking, netted $8.5 billion last quarter, despite logging just $7.9 billion in sales. Sure, Delta may owe this honor to an $8 billion one-time tax credit, but the coupling of rising sales, traffic, and capacity with falling fuel costs and reduced debt make this stock hard to ignore.

Lastly, shares of the online travel-booking company priceline.com (BKNG 2.05%) tacked on 2.3% Tuesday. Priceline stock reached a 52-week high during trading today, some of its gains likely due to the woes of a direct competitor, Expedia. In a story first broken by SearchEngineLand yesterday, Expedia is likely being temporarily punished by Google and its all-powerful search algorithm for boosting its search engine rank by using methods Google doesn't approve of. Priceline and other Expedia competitors should be the direct beneficiaries of Expedia's traffic losses from the incident.