He was believed to be wearing a light coloured baseball cap and a shiny royal blue tracksuit.
He is said not to have approached the woman but she left the area.
Officers said that a woman in her 50s was walking in the direction of the Welsh Bridge when she noticed a man standing close to the hedges at the bottom of Quarry View exposing himself.
Officers are keen to speak to anyone who saw the incident or anyone who was in the area at the time.
Police said the incident took place in broad daylight, close to the river path near Water Lane and New Street in the Frankwell area of the town, between 3.25pm and 3.35pm on Monday, October 2.
Anyone with information can call West Mercia Police on 101quoting incident number 473S of October 2. Alternatively, contact Crimestoppers anonymously on 0800 555111 or at crimestoppers-uk.org