The woman was walking alone on Roseville Avenue when the man approached her with his genitals exposed. He did not speak to the woman.
He is described as white, aged mid thirties, around 5ft 8ins tall and had facial stubble. He was wearing blue jeans, a black jacket and a black cap with white rim.
Officers have made extensive enquiries since the incident which happened on Tuesday, January 3 at around 9am.
As well as conducting house-to-house enquiries, police are appealing to members of the public who may have further information.
If you have any information, contact North Yorkshire Police on 101, select option 2, and ask for Dominic Holroyd (collar number 811).
Quote the North Yorkshire Police reference number 12170001363.