Slippery Oil, High-Yield Warnings Could Challenge Stocks' 'Santa Rally'

Sinking oil prices sapped what was shaping up to be sharp weekly gains for the broad stock averages early last week, leaving the major averages essentially flat when the final bell clanged. Commodities volatility isn’t likely to fade from the trading picture any time soon, especially as traders look to a holiday-shortened week ahead that could introduce bouts of spiking, low-volume volatility.