(CNN) - Beachgoers heading to the Gulf Coast this week could be greeted by the first tropical system to threaten the United States this year.
A tropical depression is expected to form late Wednesday or early Thursday from a broad area of low pressure moving slowly west over the northern Gulf of Mexico, the National Hurricane Center said.
The center upgraded the chance that the tropical depression forms within the next 48 hours from 50% to 70%.
A tropical depression is an area of thunderstorms that produces a circular wind flow with maximum sustained winds below 39 miles per hour.
If maximum sustained winds strengthen to 39 to 73 mph, the system becomes a tropical storm. And if they strengthen to 74 mph, we'd have a hurricane.
It's too early to pinpoint where this system would strike the worst or how intense it would be.
But a "general westward movement is expected as the system most likely tracks toward the Louisiana or Upper Texas coast over the weekend," CNN meteorologist Dave Hennen said.
High tides and strong winds also threaten southeast Louisiana or coastal Mississippi, especially if the system develops quickly and gains strength, the National Weather Service's New Orleans office said.
Although the storm's impact on production is expected to be minimal, Shell has evacuated all nonessential staff in the eastern drilling rigs in the Gulf of Mexico out of precaution, spokeswoman Cindy Babski told CNN.
Further action may be taken as monitoring of the storm continues, she said.
But what if the tropical depression doesn't happen? Coastal cities will still get hammered.
"Even if the system doesn't fully develop, very heavy rains are forecast along the Gulf Coast region, with up to 10 to 15 inches of rain possible along the future path of the storm," Hennen said.
CORRECTION: An earlier version of this story incorrectly said tropical depressions are assigned names.
CNN'st Monica Garrett and Michelle Lou contributed to this report.
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