The raid happened on Saturday evening at at the Co-op in Bomere Heath.
The woman, who was wearing grey trousers and a parka-style jacket with a fur hood, entered the shop at around 7.30pm and threatened staff with a gun. It is not known whether the gun was real or imitation.
The woman then made off with a quantity of cash in the direction of Sefton Drive.
No-one was injured during the incident.
Officers are carrying out enquiries and are keen to speak to the person in the CCTV as she may have information that can help with the investigation. If anyone recognises the person in the CCTV or if anyone saw any suspicious activity before or after the incident took place they are encouraged to get in contact.
The woman is described as approximately 5ft 7 to 5ft 8ins tall, of a regular build, aged in her mid-twenties. She was wearing a black parka coat with a fur line hood that she was wearing up, grey coloured tracksuit bottoms and carrying a small black rucksack. She also had a scarf covering her lower face and was wearing thin-rimmed, round-shaped glasses.
Information can be provided to West Mercia Police on 101 quoting reference 617s 301119 or alternatively information can be passed to Crimestoppers anonymously on 0800 555 111.