Several thunderstorms have popped up around New Jersey in the humidity of a Sunday afternoon.

Dark clouds over the Jackson Premium Outlets in Jackson (Dan Alexander, Townsquare Media NJ)

One storm has prompted the National Weather Service to issue a Flood Advisory for parts of Burlington & Ocean Counties as a storm with 60 mph winds, frequent lightning, heavy rain and hail the size of pennies dropped upwards of 2 inches of rain.

Several smaller storms have developed in Ocean & Monmouth counties with brief downpours.

Fox Philadelphia meteorologist Justin Ryan says a kind of boundry between the sea breeze off the ocean and the west winds inland is helping the storms develop around Route 9. Ryan warns the storms are slow moving and could cause street flooding.

More thunderstorms are expected to form overnight and on Monday.

The storms have caused 30 minute delays at Newark, Kennedy and LaGuardia while Philadelphia reports 15 minute delays.