Up to 10 Inches of Rain Expected in Southeastern Florida

A confluence of storm systems developing in the Gulf of Mexico and off the east coast of Florida was set to drive a consistent pattern of heavy rainfall in the Miami area Wednesday into Thursday, which could lead to flash flooding, potentially exacerbated by the high tides.

There is a moderate risk of widespread excessive rains of three to eight inches, which could lead to flash flooding from the Florida Keys through Miami and Fort Lauderdale and up to Boynton Beach. The computer forecast models show that there could be significant rainfall within the confines of the Keys on Wednesday morning, extending north in the afternoon, forecasters with the Weather Prediction Center said.

Some uncertainty in the forecast

Even though the flooding rains were imminent Wednesday morning, forecasters with the National Weather Service in Miami said there was still some uncertainty regarding the timing of the heaviest precipitation and the exact placement of the highest amounts. It depends on how fast the storm system develops off Florida’s southeast coast, but their best indication is that the bulk of the rainfall will be Wednesday afternoon through early Thursday morning.

Despite these deviations, forecasters with the Weather Prediction Center said the models show a solid 90 percent probability for five inches of rainfall or greater across the upper Keys into a zone stretching from Homestead up to Miami, giving them confidence the heavy rain will fall.

High tides and saturated soils could make it worse.

Much of this region already has saturated soils from recent rain, especially in Broward and southern Palm Beach Counties, where three to six inches of rain fell on Tuesday. The ground acts like a sponge: If you keep adding water to it, eventually, it can’t hold anymore.

It all depends on the timing, forecasters with the Weather Office said, but if heavy rain also falls around periods of high tide in some coastal communities, the water will have trouble receding. The tides aren’t relatively as high as they have been as the king tides peaked last month, but with the new moon and a strong onshore breeze, they will be moderately high Wednesday.

When will it end?

This will most likely last only 24 hours. As the storm system moves past the area and up the coast, things should begin to subside Thursday evening. Conditions should gradually improve with drier air filtering in cooler air pushes through the region.

As of Wednesday morning, it was too early to tell if the system will bring significant rain along the East Coast as it moves north in the coming days.