"Some areas (we don't know where) could get up to 25 inches of rain. That's a real problem," National Hurricane Center Director Ken Graham said.
He says widespread areas could see 15 to 20 inches of rain.
"It is really important to remember that if it is a tropical storm or becomes a hurricane, it won't matter... because really we are looking at a lot of impacts associated with the rainfall."
National Weather Service New Orleans Meteorologist in Charge Ben Schott agrees that rain is the greatest concern.
"Rainfall and flooding is going to be the number one threat with this," he explained.
Schott says they are issuing a warning now, which is not normal.
"We have a high risk for extreme rainfall, and that is something that we don't issue we usually especially three days out. That is what we have done today."
He says the New Orleans metro is in the crosshairs for flooding rain.
"The heaviest rainfall will be on the eastern side of this storm, and right now New Orleans and Southeast Louisiana are on the eastern side of this storm."
Schott noted, however, the track remains somewhat uncertain... so that could change.
The current forecast track calls for a landfall Saturday near Morgan City, Louisiana as a minimal hurricane.