KEY MESSAGES: 1. The western eyewall of Matthew, which contains hurricane-force winds, is now moving over the northern coast of Georgia and the southern coast of South Carolina and should spread up the coast during the day. 2. Hurricane winds increase very rapidly with height, and occupants of high-rise buildings along the coast 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. 3. The water hazards remain, even if the core of Matthew remains offshore. These include the danger of life-threatening inundation from storm surge, as well as inland flooding from heavy rains from Florida to North Carolina. 4. 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.