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
Winter weather advisory Snow Advisory, specific for when snow and blowing snow were the only hazards expected in the advised area. The Winter Weather Advisories for Snow, for Sleet, for Blowing Snow, and for Snow and Blowing Snow, respectively, have since replaced them. Because of the changes with the 2008-09 winter storm season, several varieties have been noted throughout the US. Also to be noted: Winter weather advisory A Winter Weather Advisory is issued by the National Weather Service of the United States when a low pressure system produces a combination of winter weather (snow, freezing rain, or sleet) that presents a hazard,