The past 15 years have seen marked progress in observing, understanding, and predicting weather. At the same time, the United States has failed to match or surpass progress in operational numerical weather prediction achieved by other nations and failed to realize its prediction potential; as a result, the nation is not mitigating weather impacts to the extent possible. This book represents a sense of the weather community as guided by the discussions of a Board on Atmospheric Sciences and Climate community workshop held in summer 2009. The book puts forth the committee's judgment on the most pressing high level, weather-focused research challenges and research to operations needs, and makes corresponding recommendations. The book addresses issues including observations, global non-hydrostatic coupled modeling, data assimilation, probabilistic forecasting, and quantitative precipitation and hydrologic forecasting. The book also identifies three important, emerging issues--predictions of very high impact weather, urban meteorology, and renewable energy development--not recognized or emphasized in previous studies. Cutting across all of these challenges is a set of socioeconomic issues, whose importance and emphasis--while increasing--has been undervalued and underemphasized in the past and warrants greater recognition and priority today.