ATLANTA — A rainy start to the week is triggering the potential for areas of flash flooding for millions across the South.A large area of high pressure that brought an arctic chill to much of the South and East this week is moving off Florida and now, ironically, in its wake is set to push a southerly fetch of tropical moisture from the Gulf of Mexico along into the Gulf Coast.That will bring rounds of heavy rain from Sunday into Sunday night across the Lower Mississippi Valley, with some showers bringing rainfall rates of 2 inches per hour in Southern Louisiana.A reinforcing shot of moisture arrives in the South on Monday and Tuesday from a storm currently soaking the Pacific Northwest on Saturday. Most of the rain will be beneficial amounts, but heavier and persistent showers could trigger flash flooding.NOAA’s Weather Prediction Center has given a Level 2 out of 4 flash flood risk for the central Gulf Coast on Monday, including New Orleans. The risk spreads north and east on Tuesday into the Southeast and includes Atlanta and Montgomery, Alabama.Some of the heaviest rainfall totals could reach 2-5 inches along a stalling front Tuesday.Rain totals when all is said and done across Louisiana, Alabama and Georgia will add up to a widespread 3-5 inches with locally higher amounts of over 5 inches possible.Aside from the flooding threat, this rain will be beneficial for far southeastern Texas and central Alabama, which are still in severe to extreme drought.