Tropical storm Sally upgraded to a Category 2 hurricane on Monday, a day before it is set to make landfall on the U.S. Gulf Coast. The National Hurricane Center (NHC) forecasts that Sally could become a Category 3 hurricane once it hits on Tuesday.

On Monday, the storm shifted east, placing the coasts along the states of Alabama and Mississippi in its direct path. Hurricane warnings have been issued in both states. The same warnings have also been issued in areas stretching from Morgan City to Florida. Weather experts have also issued warnings of possible storm surges and flash floods along the storm's path.

Coastal areas between Louisiana and Florida are expected to see storm surges of up to 8 feet. Coastal areas between the Mississippi River and Ocean Springs are forecast to experience storm surges of up to 11 feet.

The NHC warned that the storm is expected to strengthen over the next 24 hours before it makes landfall. In a process called intensification, the NHC explained that wind speeds have increased by around 40 mph over the last 12 hours. As of today, the storm's wind speeds have reached more than 100 mph.

The National Weather Service pointed out that apart from the wind, the main concern is the storm's sluggish final approach. The agency also stated that the storm is expected to remain strong for a longer period of time as most of its circulation will be over water.

U.S. President Donald Trump has approved emergency declarations across the affected states. The White House has also already ordered the Federal Emergency Management Agency (FEMA) and the Department of Homeland Security to remain on standby to provide necessary assistance to the affected states.

In Mississippi, government officials are still deciding whether they should issue mandatory evacuations. For now, Governor Tate Reeves has urged residents to prepare for prolonged outages and heavy rains. Shelters across the state have also been opened for evacuees.

In Alabama, Governor Kay Ivey has issued a state of emergency with an order to close down all beaches and establishments close to the coast. The governor also issued a recommendation for all non-residents to immediately evacuate from low-lying flood-prone areas. In a statement, Ivey warned that the coming storm should be taken lightly.