Miami, Florida (CNN) -- The weather system known as Bonnie has been downgraded from a tropical storm to a tropical depression as it moves across Gulf of Mexico -- and there are indications it may not get too much stronger.
As of 8 p.m. ET, the system had emerged in the eastern Gulf after crossing southern Florida.
The depression was moving west-northwest at a very fast clip for such weather systems -- 17 miles an hour. It's now expected to cross over the Gulf coast, anywhere from Louisiana to southeastern Texas, late Saturday night, earlier than had been anticipated previously.
The fast pace means it won't be spending as much time over the warm Gulf water, leaving less time to build up strength.
And CNN Meteorologist Chad Myers said an area of low pressure in the Gulf has been creating some competing winds that have been pulling clouds away from the cyclone and weakening it.
Still, the hurricane center said the system may slow, and a tropical storm warning is in effect from Destin, Florida, to Morgan City, Louisiana, including Lake Pontchartrain.
And Bonnie still could bring drenching rain to Louisiana and other states along the coast and create a significant storm surge. Louisiana Gov. Bobby Jindall said his state could see up to four inches of rain and a storm surge ranging from two to five feet.
Bonnie made landfall as a tropical storm earlier Friday near Biscayne Bay in southeastern Florida, with maximum sustained winds of 40 mph. But it weakened as it crossed over the state.
Even though Bonnie has weakened, uncertainty over the weather already has hampered operations at BP's cripped well in the Gulf.
BP suspended work on a relief well to permanently seal the damaged well. And the federal official overseeing the effort, retired Adm. Thad Allen, ordered ships in the area to shore because of the choppy seas and gusty winds that Bonnie will bring. That could delay operations at the well site for 10 to 14 days. But Allen said there's enough confidence in the well's "integrity" that it will be left capped and closed during the rough weather.
Ships used to skim oil off the surface will have to come ashore as well. Hundreds have been operating off the coast.
Meanwhile, states of emergency have been declared in both Louisiana and Mississippi. The emergency declarations are intended to speed state help to local goverments that need it and allow emergency crews to respond more efficiently.
Jindal said Thursday afternoon it's "good for Louisiana" that the weather system is moving so fast, since it may not strengthen significantly and is likely to move across Louisiana fairly quickly.
Still, he said about a half dozen Louisiana parishes have called for voluntary evacuations from low-lying areas and mobile home parks.
The Louisiana Department of Children and Family Services encouraged residents Friday to prepare for the storm by pre-applying for Disaster Supplemental Nutrition Assistance Program benefits, previously known as Disaster Food Stamps.
The program offers help buying groceries for those who do not regularly receive nutrition assistance but who are affected by lost wages or damages because of a disaster. Officials said that pre-applying does not guarantee benefits but is designed to prevent long waits.
The weather system earlier drenched the Bahamas, Puerto Rico, Haiti and the Dominican Republic as it moved from the Caribbean to the Atlantic.
When it reached Florida, residents in Cutler Bay saw tree branches littering the roads as Bonnie passed through Miami-Dade County.
"It was pouring rain for four to five hours straight," said Matthew Slack, a bartender at Cutler Bay Sports Bar and Grill. But he added, "It's not that bad. It's like a regular summer storm in Miami."
The storm also slowed business in southern Florida.
"We've had a lot of people call and say they might have to cancel due to the storm," said Susie Bishop of Continental Inn Condominiums in Marathon, Florida. "I had a few people leave a few days early."
CNN meteorologist Sean C. Morris contributed to this report.