The assailant is described as Caucasian, 18-22 years old, 5'9", thin and "clean-cut looking," wearing a dark stocking cap, dark wool coat or sweatshirt, sunglasses and jeans.
Highland Park police say they stepped up patrols in the area following the incident.
Lake Forest police are also investigating a similar robbery that took place November 20.
Anyone with information is asked to call police.
