A tropical storm watch was hoisted Thursday afternoon for all of South Florida as a system gathers strength in the southern Gulf of Mexico.
A tropical storm watch means tropical storm-force winds of at least 39 mph are possible within the next 48 hours.
The system, dubbed Potential Tropical Cyclone One, is forecast to become a tropical depression or storm by Friday. It is expected to dump heavy rain across south Florida over the weekend, potentially as much as a foot, the National Hurricane Center said, which could lead to flash flooding.
The National Weather Service in Miami said that "it is becoming increasingly likely heavy rainfall will occur across South Florida Friday and Saturday."
"With some areas across South Florida already saturated from recent heavy rainfall, the potential for flash flooding continues to be the primary impact with this disturbance," the Weather Service said.
The Weather Service forecast office in Key West agreed, noting that "the primary impact will likely be localized flooding due to rainfall, rather than destructive storm surge or winds."
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However, strong to severe thunderstorms are also a threat, the Weather Service said, and isolated tornadoes will also be possible.
The tropical storm watch is in effect for the west coast of the Florida peninsula south of Longboat Key and for the east coast of the Florida peninsula south of the Volusia/Brevard County line, including Lake Okeechobee.
A tropical storm watch has also been issued for all of the Florida Keys.
The storm would become Tropical Storm Alex if its sustained winds reach 39 mph.
STORM TRACKER: Track the path of the storm
This article originally appeared on USA TODAY: Tropical storm watch issued for South Florida as hurricane season begins