The 51-year-old victim as walking along a footpath in the direction of the Priesthill pitches when the culprit approached her and exposed himself before walking off.
The suspect is white, 5ft 8ins, aged 28 to 34 and is of medium build with fair hair which has blond highlights.
He was wearing a black waterproof jacket with a brown suede patch at the elbow, light-coloured blue heans and white trainers - one of which has a loose sole which was flapping on the ground.
Police Constable Alan Gardner said: “This has been an extremely distressing incident for a woman who was heading out to meet up with a friend.
“The incident occurred on the footpath underneath railway arches near to Priesthill Pitches, an area regularly used by local people out walking with their dogs.
“I am appealing to anyone who may have been in the area around the time of the incident or anyone who thinks they recognise the description of the man to contact us as soon as possible.”
Anyone with information is asked to call officers at London Road Police Station via 101, quoting reference number 4408 of 24 June 2017.
Alternatively, call Crimestoppers on 0800 555 111 where information can be given anonymously.