January 31 – February 2, 2011 North American blizzard fell as freezing rain in the Philadelphia suburbs, a mixture of sleet and freezing rain in Berks County and the Lehigh Valley and mainly a snow and sleet mixture in the Poconos. Overnight colder air moved in aloft in over the Poconos and precipitation changed back to all snow for a few hours. Toward sunrise on the 2nd, this process started to reverse at both the surface and aloft. Warmer air was moving north again and the freezing rain changed to plain rain across the Philadelphia suburbs and Berks County around 8 a.m. EST and the Lehigh Valley around 9
Hail spike rain core. Since hail cores are most intense at higher elevations, hail spikes usually appear at the levels aloft that accompany the most intense hail. Because of this, hail spikes are usually not seen at lower elevations. Another restriction to detection is that the signal of the radar beam has to do multiple reflections, each time weakening it, and are therefore usually noticeable only in extremely large hailstone cases. In rare cases more than one hail spike has been documented with a single storm in one volume scan. This indicates that more than one hail core exists in the same