But the broad storm system is expected to bring heavy rains across the entire northern Gulf Coast starting well before landfall.
The storm's approach also triggered mandatory evacuations of some small, sparsely populated Gulf Coast barrier islands in one Florida county. Strong onshore winds may bring higher than normal water levels along the coast which could create coastal flooding. Storm surge was a bigger threat north of the Tampa Bay area, with flooding possible in and north of Crystal River, the weather service said.
The tail of Alberto shifted into the Bahamas last night, so the most intense flow of tropical moisture avoided South Florida Sunday. "Rainfall amounts of 5 to 8 inches, and possibly locally up to double these amounts are possible in this area with this event", the NWS said.
Combined with the above average rainfall we've already seen so far this spring, additional rain could create flooding issues in the upcoming week along area rivers. The black line, when selected, and dots show the National Hurricane Center (NHC) forecast track of the center at the times indicated.
Subtropical Storm Alberto - the first named storm of the 2018 hurricane season that starts June 1 - prompted Florida, Alabama and MS to launch emergency preparations Saturday.
MS governor Phil Bryant has declared a state of emergency as the storm moves toward the state's coast. According to the National Weather Service, almost half of all flash flood fatalities are vehicle-related.
"These swells are likely to cause life-threatening surf and rip current conditions", the National Hurricane Centre in Miami said in a statement.
The subtropical storm, the first named storm of the season, is expected to spread tropical storm conditions along the west coast of Florida Sunday. Because of expected deteriorating weather, the sandbag distribution points will not be open Sunday, the county said.
The slow-moving system is expected to cause wet misery across the eastern U.S. Gulf Coast over the holiday weekend.
The system was moving north at 13 miles per hour.
The National Weather Service in Huntsville said isolated rain showers on Monday morning could become more numerous by the afternoon as Alberto moves closer to north Alabama.