It happened around 12:30 a.m. on Sunday, September 29, as the woman was walking down the stairs into the 1 train station at 86th Street and Broadway.
Police say the suspect pushed her up against a wall and groped her.
NYPD officers have been patrolling the station, and there are signs posted, warning commuters about the assault.
The individual is described as a man with short black hair, approximately 5'10" tall, and a medium build. He was last seen wearing a blue baseball hat, a white shirt, a gray jacket and gray sneakers.
Anyone with information in regard to this incident is asked to call the NYPD's Crime Stoppers Hotline at 1-800-577-TIPS (8477) or for Spanish, 1-888-57-PISTA (74782).
There is a $2,500 reward for information leading to an arrest.
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