Sales uncertainty is a central problem for marketing management. Marketers tend to focus on expected sales, rather than short-term time-varying oscillations. With long supply-chain streams, the Bullwhip effect can turn retail sales volatility into a major problem for upstream companies. While it has been recognized that conditional expected sales change through time (for a review see Dekimpe and Hanssens, 2000), marketers have not yet started to modeling explicitly time variation of sales’ conditional variances. In this paper we focus on this issue, modeling and forecasting time-varying retail sales and marketing mix volatility and their crossed effects within brand, and between competitive brands. We analyze up to 6 product categories sold by Dominick’s Finer Foods, finding volatility and co-volatilities in all of them. We discuss managerial implications for brand management and competitive strategy.