(CNN) Tropical Storm Barry presents New Orleans with an unprecedented problem, according to the National Weather Service.
The Mississippi River, which is usually at 6 to 8 feet in midsummer in the Big Easy, is now at 16 feet, owing to record flooding that's taken place this year all along the waterway.
In the meantime, Barry is spinning away in the Gulf of Mexico, threatening a storm surge of 2 to 3 feet at the mouth of the river, said Jeffrey Graschel, a hydrologist with the weather service's Lower Mississippi River Forecast Center in Slidell, Louisiana.
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The unusual confluence of factors adds up to a forecast that has the river cresting Saturday at 19 feet, a level not seen since February 1950 and about 2.3 feet shy of the record set in April 1922, the weather service said Thursday.