At the time of the Global Precipitation Measurement (GPM) Core Observatory overpass (April 1, 2017, 0550 UTC), the storm's center of low pressure was south of Long Island. At the mid-levels of the atmosphere, the circulation was centered over northeast Pennsylvania. This led to a classic overrunning, warm conveyor setup, which happened when the counterclockwise low level flow drew in cold air out of the north/northeast (hence "Nor'easter") from Canada.
For six weeks in Ontario, Canada, scientists and engineers lead a field campaign to study the science and mechanics of falling snow. The datasets retrieved will be used to generate algorithms which translate what the GPM Core satellite "sees" into precipitation rates, including that of falling snow. Ground validation science manager Walt Petersen gives a summary of the GCPEx field campaign. Field campaigns are critical in improving satellite observations and precipitation measurements.