A forecast for Hurricane Irma has shifted the trajectory of the mega-storm slightly westward, which may mean direct hits on the Florida Keys and worst-case scenarios for the cities of Naples, Fort Myers and possibly Tampa.
As of late Friday East Coast time, modeling from the NBC Weather Unit now expects catastrophic wind and storm damage in the Keys early Sunday morning. Marco Island, Naples, Cape Coral and Fort Myers are likely to be struck later on Sunday.
A shift west would still mean that the east coast of Florida sees hurricane gusts and damage, NBC said, but it makes catastrophic effects less likely from Miami northwards.
Irma, one of the most powerful Atlantic storms in a century, strengthened and made landfall on an island chain in Cuba as a category 5 storm, according to a late Friday night tweet from the U.S. National Hurricane Center (NHC).
The NHC also extended hurricane warnings northward along the Florida peninsula.
Earlier on Friday, the “extremely dangerous” hurricane was downgraded from a category 5 to a category 4, but it still packed winds as strong as 155 miles per hour at that time, the NHC said in an advisory.
Irma has already lashed the Caribbean with devastating winds and torrential rain, leaving behind at least 21 deaths and a swath of destruction.
Dozens of cities and counties in increasingly-northern regions of Florida are issuing mandatory evacuations that have affected millions of residents. Some highways have ground to a halt from congestion as evacuees flee the most dangerous hurricane areas.
Florida Governor Rick Scott is scheduled to deliver an update on the storm on Saturday morning from Sarasota.
A mandatory evacuation on Georgia‘s Atlantic coast was due to begin on Saturday, Governor Nathan Deal said.
— NBC News’ Bill Karins, and CNBC’s Kevin Breuninger and Spencer Kimball contributed to this report
