PHILADELPHIA - The National Weather Service has issued Flash Flood Watches taking effect overnight ahead of a coastal low that could develop into a tropical depression or storm.The Flash Flood Watch will be in effect from midnight tonight through Friday afternoon.According to the National Hurricane Center, the area of low pressure is located near the North Carolina Outer Banks this afternoon has a 90-percent chance of becoming a tropical depression or storm as it moves north-northeastward along the Mid-Atlantic coast.Heavy rain associated with that coastal low is expected to start late tonight and continue through Friday evening.For South Jersey and Delaware, widespread amounts of 1 to 3 inches are likely with locally higher amounts.