* WHAT. Minor saltwater flooding will continue across the Florida Keys overnight through Wednesday afternoon, especially around the times of high tide. Major saltwater flooding of 1 to 3 feet above ground level at the lowest elevation areas and shoreline is expected Wednesday evening through Thursday evening, with strong southeast to south winds impacting the Florida Keys as Tropical Storm Helene moves northward through the eastern Gulf of Mexico and intensifies into a major hurricane. * WHERE. The Florida Keys. * WHEN. Until midnight EDT Thursday night. * IMPACTS. Through Wednesday afternoon, minor saltwater flooding of low elevation streets and lots is likely, with little relief during low tide. Some storm drains will overflow, and some seawalls and docks will be overtopped. Boaters can expect less clearance under fixed bridges. Motorists should remember that persistent puddles around the times of high tide are almost certain to contain a mix of saltwater. For Wednesday evening through Thursday evening, storm surge flooding will cause numerous roads to be closed. Low lying property including homes, businesses, and some critical infrastructure will be inundated. Flooding may extend over streets and low elevation properties a few blocks from the shoreline. Some shoreline erosion will occur. * ADDITIONAL DETAILS. The initial storm surge flooding threat will be primarily on the oceanside beginning Wednesday evening, with a possible Gulf side surge occurring on Thursday into Thursday evening as winds shift to south or southwest.