The National Hurricane Center in Miami says a large low pressure system located near the northern coast of the Yucatan Peninsula has a 70 percent chance of developing into a tropical cyclone within the next 48 hours.
Heavy rains and localized flooding are possible across South Florida through Saturday.
There's 70 percent chance of rain on Saturday, 60 percent on Sunday and 50 percent on Monday.
An Air Force reserve aircraft is scheduled to investigate the system on Friday afternoon.
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