Authorities were warning people in a handful of towns outside of New Orleans to get out early Thursday ahead of a storm surge brought on by hurricane-turned-tropical storm Isaac as it dumped more than 20 inches of rain in some areas. The warnings for residents in Washington Parish followed news that the Bogue Chitto River was expected to rise by 14 feet overnight, while National Guard troops looked for people stranded in St. John Parish after thousands were forced to flee when the surge forced water over the banks of Lake Pontchartrain.