sentences:  The 1997 storm was a classic example of a "rain on snow" event, during which a warm tropical storm melted existing snowpack at lower and middle elevations, effectively doubling the volume of runoff.Prior to the New Year's storm, the winter of December 1996 had also been one of the wettest ever recorded, saturating the ground and depositing a considerable amount of snow.The Bureau of Reclamation's Safety of Dams Program determined the risk of flooding in the Sacramento area made it one of the most at-risk communities in the United States.