A state of emergency has been declared in New York City as strong storms have brought flash flooding. Torrential rain caused flooding that closed roads, and disrupted subway service as “dangerous and life-threatening” rainfall surged across the  New York City.   Many of the city’s subway systems, streets, and highways have flooded, while at least one terminal at LaGuardia Airport closed on Friday.     Up to five inches of rain fell in some areas overnight, and as much as …