Sally will become a slow-moving hurricane by Monday morning

Tropical Storm Sally is forecast to strengthen into a strong Category 1 or weak Category 2 hurricane as it approaches the Gulf Coast Monday morning. For 48 hours before landfall, the greatest danger will be the storm surge and torrential rains.

The 4:00 p.m. advisory from the National Hurricane Center places Tropical Storm Sally about 165 miles (265 kilometers) south of Panama City, Florida, and 215 miles (345 kilometers) east-southeast of the mouth of the Mississippi River.

Sally is moving toward the west-northwest near 9 mph (15 kph) and this motion is expected to last throughout the night. The storm is moving to the west-northwest at close to 9 mph (15 kph). Maximum sustained winds at 4:00 p.m. are near 60 mph (95 kph) with higher gusts. The minimum central pressure is 996 mb (29.41 inches).

On Monday and Monday night, Sally will take on a west-northwestward motion, followed by a further decrease in forward speed and a turn to the northwest Monday night and Tuesday. This decrease in speed could spell trouble for people along the coasts of Florida and on up to the southeastern Louisiana and southern Mississippi coast.

Tropical-storm-force winds extend outward up to 125 miles (205 km) primarily to the east of the center. And the eastern side of Sally will produce heavy rains, especially from the Florida Keys to Sarasota. Key West saw 4 inches of rain in one hour that caused flooding overnight and additionally, Key West observed 9.37 inches of rain Saturday, reports ABC News.

Water will be the big danger

Sally's outer bands should reach the Gulf Coast Monday morning - However, the storm will stall along the coast until Wednesday, making little progress inland. This inertia will produce up to 48 hours of storm surge and rainfall which could be a very dangerous situation.

The latest forecast now calls for up to 20 inches of rain along the Gulf Coast. As with all hurricanes, this rainfall will be heaviest east of the center and could cause major flash flooding. Storm surge is forecast to be up to 11 feet, again east of the center.

Louisiana Gov. John Bel Edwards declared a state of emergency Saturday evening ahead of Sally's arrival, and on Sunday, he said he had spoken with President Donald Trump and will submit a pre-landfall federal declaration request, reports CNN News.

"While we ultimately don't know where Sally will make landfall, much of Southeast Louisiana is in the storm's cone and the risk of tropical storm force or hurricane strength winds continues to increase. This storm has the potential to be very serious," Edwards said in a news release.

Three jails with 1,200 inmates in total have been evacuated, Edwards said Sunday, and at least one nursing home is evacuating. In New Orleans, Mayor LaToya Cantrell issued a mandatory evacuation order for residents outside of the city's levee protection system. The evacuation will begin Sunday at 6 p.m. for the areas of Venetian Isles, Irish Bayou and Lake Catherine.

So far this season, there have been 18 named storms. The average for an entire season is 12. Early in the season, forecasters called for a very active season. After Sally, there are only three names left on this year's official list: Teddy, Vicky, and Wilfred. After that, the NHC will move on to using the Greek alphabet.