A constant flow of tropical moisture associated with Tropical Storm Alberto will usher in another couple days of showers and thunderstorms across much of the Southeast. There won’t be much of a storm system responsible for this rain, although there will be a slowly-deepening upper-level low over the northern Gulf Coast that will enhance the rain and make it more widespread. This will also pull in more deep moisture from the Caribbean Sea. For midweek, it will be more low instability and mild temperatures that will drive the precipitation. It’s not until the weekend when a tropical or subtropical cyclone moves onshore and brings a few days of widespread rain.
On Thursday, conditions will be quite similar, although there will be an uptick in the aerial coverage of the precipitation. In the morning, a few spotty storms will be found across the southeastern US. It’s not until the afternoon when storms will begin to blossom and impact the region. Scattered showers and thunderstorms will be the common theme Thursday afternoon and evening, some of which may drop heavy rain. The greatest rainfall totals are expected to be seen across the Florida Peninsula, due to the higher moisture content. The greater the precipitable water, as shown in the European model image below, the better the chance for heavier rain, as there will be more water available in the atmosphere.
As we head into Saturday, the rainfall will begin to become more widespread along the Gulf Coast from Louisiana through Florida. Isolated and scattered storms in the morning will evolve into widespread showers and thunderstorms for the latter half of the day across the Southeast. Once you get up toward the Mid-Atlantic and Ohio River Valley, conditions will be much drier.
Rainfall through Friday night will be heavy in some areas, but not as heavy as the weekend. Widespread totals of one to two inches can be expected, which will lead to flooding in some areas. The risk for flooding is especially high for the towns that have already received over half a foot of rain so far this month.
By the weekend, the heavy rain will move in. We detail this rain in our tropical update article on Invest 90L here, as well as in our Memorial Day Weekend forecast here.