At approximately 8.10pm, a masked male entered the shop in Moss Park brandishing a metal tool in front of a staff member.
The male made comments towards the staff member before trying to get behind the counter.
A female customer in the shop tried to stop him before he jumped over the counter, grabbed an item and ran away.
The suspect wore a green hooded top, with the top pulled up, black trousers and dark shoes.
His face was fully covered with a black mask.
Detective Sergeant Ballentine said: “This was a brazen act that was really distressing and shocking for those impacted, in particular the female staff member who was left badly shaken.
“This was a despicable crime.
“Fortunately, at this time, we have no reports anyone was physically injured during the course of this despicable crime.
“We are appealing to anyone who was in the area at the time who believes they saw a male matching the description of the suspect, who saw him enter the shop or run off.
“We would also ask anyone with CCTV or doorbell cameras to check footage between 8:00pm and 8.15pm.”
The number to call with information is 101, quote reference 321 of 12/09/23.
Information can also be provided to Crimestoppers anonymously on 0800 555 111, or online at www.crimestoppers-uk.org.