08/26/2012 06:58 am ET Updated Aug 27, 2012

Tropical Storm Isaac Forecasts, Path And Updates: Sunday (VIDEO, PHOTOS)

Tropical Storm Isaac did not strengthen into a hurricane while passing through the Florida Keys, though it is still expected to do so.

The center was about 75 miles west-southwest of Key West at 11 p.m. Sunday, churning west-northwest into the Gulf of Mexico at 14 mph with maximum sustained winds of 65 mph.

Isaac is now expected to become a hurricane "in a day or two" while approaching the northern Gulf Coast on Tuesday, said the latest National Hurricane Center advisory. A hurricane warning was extended west along the Louisiana east coast to include Lake Pontchartrain and metro New Orleans, where the mayor declared a state of emergency.

Though Isaac's tropical storm-force winds extend 205 miles from its center, there were no major reports of damage in Miami-Dade or Monroe Counties, and hardy Keys residents described Isaac as "just a summer day in Key West."

Still, more than 15,980 people were reported without power in Miami-Dade and Broward counties, and almost 600 flights were grounded in Miami and Ft. Lauderdale.

National Weather Service meteorologist Robert Molleda told the Miami Herald that though fast-moving squall lines could still move through South Florida Sunday, tropical storm-strength gusts should clear South Florida by midnight.

Hurricane, tornado, and tropical storm watches have been canceled for Miami-Dade County.

Tropical Storm Isaac Heads To Florida