The National Hurricane Center says Tropical Storm Gordon made landfall late Tuesday night just west of the Alabama-Mississippi border.
The Miami-based forecasting center says Gordan, which formed Monday morning near the Florida Keys, was packing maximum sustained winds of 70 mph when it hit land. It never achieved hurricane status.
Authorities warned of possible flash floods. Pensacola International Airport reported more than 4 inches of rain Tuesday night, the heaviest total so far along the Gulf Coast.
The storm was forecast to quickly weaken as it moves inland across Mississippi, Louisiana and into Arkansas through Thursday.
Governors of Alabama, Mississippi and Louisiana declared states of emergency to better mobilize state resources and National Guard troops for the storm. Mississippi shut down a dozen Gulf Coast casinos. Workers on at least 54 oil and gas production platforms were evacuated.
As of 4 a.m. Wednesday, Gordon was some 20 miles northwest of Hattiesburg, Miss., moving northwest at 14 mph. Its maximum sustained winds were down to 40 mph.
The National Hurricane Center discontinued all Gordon-related tropical storm and storm surge warnings and tropical storm watches.
Gordon was expected to diminish to a tropical depression later Wednesday morning.
Still, forecasters say Gordon's remnants could cause flash flooding across parts of seven states - as far north as southern Iowa - in coming days.
The Hurricane Center said, "Gordon is expected to produce total rain accumulations of 4 to 8 inches over the western Florida Panhandle, southwest Alabama, southern and central Mississippi, northeastern Louisiana, Arkansas, Missouri, southern Iowa and Illinois, with isolated maximum amounts of 12 inches through early Saturday. This rainfall will cause flash flooding across portions of these areas."
Tropical Storm Gordon spawned multiple possible tornadoes as it came ashore late Tuesday. The National Weather Service issued several tornado warnings in south Alabama and the Florida panhandle after radar indicated possible twisters associated with the storm.
There were no immediate reports of damage.
The Associated Press contributed to this report.