Nicholas has become post-tropical, the National Hurricane Center said.
According to the NHC's latest update, Nicholas is 40 miles south of Alexandria, Louisiana. The storm has maximum winds of 15 mph.
Continued gradual weakening is forecast during the next 36 hours with the low center eventually dissipating.
Flash flood watches are in effect along the central Gulf Coast from portions of southeast Louisiana, across southern Mississippi and Alabama, to the Florida Panhandle.