The storm could inundate more than one-fourth of that coast's dunes, causing flooding behind the protective dune line, said Kara Doran, leader of the USGS Coastal Change Hazards Storm Team.
At 11 a.m. ET (1500 GMT) on Tuesday, Michael's center was about 335 miles (535 km) south-southwest of Apalachicola, Florida, heading north at around 12 mph (19 kph), the NHC said.
Michael gathered greater strength over warm Gulf of Mexico waters throughout the day on Tuesday as it jumped from a Category 2 to Category 3 on the five-step Saffir-Simpson wind scale. The National Hurricane center says the Florida Panhandle should prepare for life-threatening storm surge, destructive winds and heavy rainfall.
Damaging wind gusts in the area could reach up to 60+ miles per hour during the overnight period Wednesday into Thursday. Residents in these areas should follow advice given by local officials, and keep tabs on live updates, which are available from CNN.
The last major hurricane to hit the Panhandle was Hurricane Dennis in 2005, according to hurricane center data. "It looks like another big one", he added. We handle them very well. It never ends but we are all prepared and hopefully it won't be as bad as it's looking.
Scott has already declared a state of emergency in 35 counties, and the Florida National Guard has activated 1,250 troops for planning, logistics and emergency response.
In a 5 p.m. update on October 9, the National Hurricane Center (NHC) said Michael has strengthened to a "major hurricane" and has life-threatening storm surge, hurricane-force winds, and heavy rainfall.
Georgia Governor Nathan Deal on Tuesday issued a state of emergency declaration for 92 counties in the state.
Tallahassee's Democratic Mayor Andrew Gillum, who is campaigning to succeed Scott as governor in next month's elections, suspended his campaign and returned to the state capital to oversee storm preparations.
NHC Director Ken Graham said Michael represented a "textbook case" of a system growing stronger as it drew near shore, in contrast to Florence, which struck North Carolina last month after weakening in a slow, halting approach.
It made landfall on the coast as a Category 1 hurricane on Sep 14 and drenched some parts of the state with 40 inches of rain.
Hurricane Michael is intensifying now in the Gulf of Mexico, but its impact on eastern Virginia is still uncertain.
Much of the state saw the "real thing" past year, when Hurricane Irma force more than 6 million evacuations, flooded cities and left millions without power. We can rebuild your house, but we cannot rebuild your life.