Antony Saglianiaccuweather.comA plume of moisture surging northward from the Gulf of Mexico and Caribbean Sea will bring widespread tropical downpours across a large part of the Southeast on Wednesday into the Fourth of July.Some of the areas that have the highest potential for flooding include Tampa, Fla.; Tallahassee, Fla.; Atlanta, Ga.; Athens, Ga.; Greenville, S.C.; Knoxville, Tenn. and Charleston, W.Va.Accuweather.com meteorologists are especially concerned for dangerous flash flooding in the higher elevations of the southern Appalachians, such as Andrews, N.C.; Asheville, N.C. and Greenville, Tenn.While widespread river flooding is not likely from this event, there is considerable concern for rapid, dangerous flash flooding of low-lying areas, urban areas, areas with poor drainage and areas that are near smaller creeks and streams.Numerous blinding downpours will cause severe restrictions to normal driving speed as low visibility and water-logged roadways bring the risk of hydroplaning.Those traveling I-81, I-85 or I-40 in the southern Appalachians will likely see significant delays this afternoon and evening. The same can be said for I-10 across the Florida Panhandle.Arrival and departure delays at major airports like Atlanta’s Hartsfield International may also be common, especially as drenching storms engulf the region in the afternoon and evening hours.This situation has the potential to be particularly dangerous in some areas. It is important to remember that flash flooding can be life-threatening. Not every location will have flash flooding, and some areas may not receive much rainfall at all, but that will not be the case in other, less lucky locations.Tremendous rainfall in a short amount of time can cause flooding of areas that you might not even think can flood. Yards and basements can become more like lakes and swimming pools. In towns with hilly terrain, streets can easily be turned into rushing rivers.It only takes a few inches of swift-moving water to sweep a person from his feet, and only 18 inches to lift a vehicle and wash it away.The threat for excessive rainfall and flash flooding will slowly shift to the west on Wednesday night into the Fourth of July. Alabama, Tennessee and Kentucky will be the areas with the highest risk.