One of the later snowfalls in Philadelphia's modern climate history -- a trace event -- occurred on April 23rd, 1986. This slow-moving coastal storm brought rain to the region on the 22nd but as colder air drained in its wake late in the evening hours, rainfall transitioned over to a mix of rain and snow...even all snow briefly into Philadelphia as temperatures were near freezing. Flurries lingered around the city into the midday hours. Temperatures struggled to climb above 40 during the daylight hours on the 23rd, with the high in the city of 43 just missing the record for coldest high of the date (42) from the late 1800's.
they did in the Poconos. As a result, the storm dumped between ten and thirty inches of snow across the Pocono highlands (depending on which reports you read...reports vary on the snowfall...but at least a foot did fall in many spots) due to the slow moving nature of the system and the plentiful precipitation that fell across the higher terrain.
such as 5/9/1977) -- it was still a rather late season event in comparison to the "norm".