It happened last Friday inside the store located in the 1600 block of West Nedro Avenue.
Surveillance video shows the suspect storming into the store armed with a handgun.
He then jumped over the counter and through a window to the where the clerk was sitting.
The suspect ordered the 34-year-old female clerk to stay put as he cleaned out the cash register.
The man then jumped back over the counter, put his gun in his waistband, and checked for witnesses before walking out of the store.
The clerk was not hurt.
If you have any information about this crime or this suspect, please contact: Northwest Detective Division (215)686-3353/335