KEY MESSAGES: 1. Matthew is likely to produce devastating impacts from storm surge, extreme winds, and heavy rains in the northwestern Bahamas today, and along extensive portions of the east coast of Florida tonight. 2. Evacuations are not just a coastal event. Strong winds will occur well inland from the coast, and residents of mobile homes under evacuation orders are urged to heed those orders. 3. Hurricane winds increase very rapidly with height, and residents of high-rise buildings are at particular risk of strong winds. Winds at the top of a 30-story building will average one Saffir-Simpson category higher than the winds near the surface. 4. When a hurricane is forecast to take a track roughly parallel to a coastline, as Matthew is forecast to do from Florida through South Carolina, it becomes very difficult to specify impacts at any one location. Only a small deviation of the track to the left of the NHC forecast could bring the core of a major hurricane onshore within the hurricane warning area in Florida and Georgia. Modest deviations to the right could keep much of the hurricane-force winds offshore. Similarly large variations in impacts are possible in the hurricane watch and warning areas in northeast Georgia and South Carolina. 5. The National Hurricane Center is issuing Potential Storm Surge Flooding Maps, and Prototype Storm Surge Watch/Warning Graphics for Matthew. It is important to remember that the Potential Storm Surge Flooding Map does not represent a forecast of expected inundation, but rather depicts a reasonable worst-case scenario - the amount of inundation that has a 10 percent chance of being exceeded. In addition, because the Flooding Map is based on inputs that extend out only to about 72 hours, it best represents the flooding potential in those locations within the watch and warning areas in Florida and Georgia.