Flash flood risk increases late week as tropical moisture surges into Florida
A surge of tropical moisture will produce rounds of heavy rainfall and increase the risk of flooding for the Panhandle and North Florida by the weekend.
Earlier Wednesday, surface analysis depicted a stalled frontal boundary that was draped across the Mid-South. This feature is forecast to gradually push south through the week, acting as a focus for shower and thunderstorm development. Along the stalled frontal boundary, models indicate the development of a cutoff area of low pressure in the northern Gulf of Mexico by late week. The nearly stationary front in conjunction with a slow-moving area of low pressure will contribute to the potential for rounds of heavy rain and flooding as atmospheric moisture surges across northern and central Florida.
High resolution model guidance suggests that bands of heavy rain will develop as early as Thursday, especially from the Emerald Coast through the Nature Coast. This area will be most susceptible to the risk for flash flooding over the next five days, as heavy rainfall has inundated this region for several weeks. Since early August, parts of the Panhandle and locations north of I-4 have seen a rainfall surplus of more than 8 inches, with a few locales receiving more than a foot of rain.
The Weather Prediction Center highlighted an area from Pensacola to Tampa to Jacksonville with a "slight" risk for flash flooding by Friday. On a 1-to-4 scale for flash flood potential, this level is a 2 and represents at least a 15-percent chance of exceeding flash flood guidance within 25 miles. Outside of that region, from Fort Myers to Orlando, a "marginal" risk for flash flooding exists. This is a 1 on the 1-to-4 scale for flash flood potential and indicates at least a 5-percent chance of exceeding flash flood guidance within 25 miles.
Widespread forecast rainfall amounts over the next seven days could approach 3 inches, with pockets of more than a half-foot possible from the Forgotten Coast to the Sun Coast. These rain totals will likely not occur at once, but rainfall rates in the heaviest bands of convection is likely to lead to some flooding through the weekend. Stay weather aware over the next seven days, especially in areas that are prone to flooding.