The suspect entered the store at about midnight, said police. He started swinging a butcher knife at the two clerks and demanded money.
He then fled on foot, dropping the knife on the sidewalk as he left.
Officers contained the area. The canine unit was called out for a track, but the suspect was not located.
The suspect is described as 5-10 with a slim build, wearing a black balaclava, black hoodie, jeans and lighter-coloured gloves.