Updated

Hurricane Michael, a "major" Category 3 storm, was becoming "better organized" and is forecast to intensify as it barrels towards Florida's Gulf Coast, where it's expected to make landfall, officials said.

The storm, moving northward at 12 mph, was about 255 miles south of Panama City, Florida, according to a 8 p.m. ET advisory from the National Hurricane Center (NHC).

With maximum sustained winds of 120 mph, Michael was forecast to drench parts of the northeastern Gulf Coast and bring "life-threatening storm surge," the advisory said. The most severe storm surge is predicted to occur from Mexico Beach to Keaton Beach, Florida, which could see as much 13 feet.

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As the storm makes landfall in the Florida Panhandle or Big Bend area, it is expected to increase to near-Category-4 strength before weakening, the NHC said.

Parts of Florida, Georgia, the Carolinas and Virginia could see “life-threatening flash flooding” as a result of severe rain, according to a tweet from the NHC.

Amid the NHC's update, Florida Gov. Rick Scott tweeted about the severity of the impending storm surge.

"Let me be clear- the storm surge that our coastal counties are facing is deadly," Scott tweeted. "DO NOT ignore warnings from local officials- this storm could kill you. We can rebuild your house, we cannot rebuild your life. If you have evacuation orders, LEAVE NOW."

Earlier Tuesday, Scott stressed that time was running out for residents to prepare.

“Hurricane Michael will be here TONIGHT. This is your LAST CHANCE to get prepared for this monstrous and deadly storm,” Scott tweeted. “The state is not taking this storm lightly and neither should any family.”

His urgent message came shortly after President Trump approved an emergency declaration in the state, extending federal resources to Florida in anticipation of the impending hurricane.

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The declaration, requested by Scott, encompasses 35 counties and “will provide important resources and assistance from the federal government, including personnel, equipment and supplies, as well as making available funding sources for emergency protective measures,” according to a news release from Scott’s office.

Scott on Monday expanded a state of emergency to a total of 35 Florida counties, the news release said.