Winter Storm and Heavy Snow in Pennsylvania, October 29, 2011

An unprecedented winter storm for late October not only dropped heavy snow across most of Eastern Pennsylvania, but caused widespread power outages and road closures as many deciduous trees still had foliage. Nearly one million utility customers in Eastern Pennsylvania lost power and power was not fully restored until November 6th. Eight people lost their lives (one directly) because of the winter storm. Except for Philadelphia and Delaware Counties, accumulations averaged 6 to 12 inches with some larger amounts over higher terrain locations. Accumulations in Philadelphia and Delaware Counties averaged 1 to 3 inches. The hardest hit areas included the Lehigh Valley, Berks County and Bucks County. Shelters, warming stations, showers and ice distribution locations were opened in the hardest hit areas. Many hotels were booked solid in those areas.

Precipitation started as snow during the early morning of the 29th in the Poconos and remained as snow throughout the event. The snow fell at its heaviest during the afternoon and ended that evening. Across the Lehigh Valley, Berks County and the northwest Philadelphia suburbs, precipitation initially started as rain during the early morning of the 29th, but as the precipitation intensity increased, it changed to snow between 8 a.m. and 9 a.m. EDT in most places. The snow fell heavy at times between 10 a.m. EDT and 4 p.m. EDT. As precipitation became lighter, it mixed with some sleet and rain, especially toward Philadelphia that evening. Precipitation ended late that evening. In Philadelphia and Delaware Counties, precipitation type was intensity driven. Precipitation started as rain during the early morning of the 29th. As waves of heavier precipitation passed over the counties, precipitation type changed back and forth between snow, rain and sleet. As the intensity lessened during that evening, precipitation changed back to rain and ended around Midnight EDT on the 30th.

In Berks County, in Temple (Muhlenberg Township), an 84-year-old man was killed when a snow covered tree fell through his house and killed him while he was sleeping on his recliner. In Lehigh County, a 60-year-old man died of carbon monoxide poisoning after using a charcoal grill to heat their home in Emmaus. A 17-year-old boy died from an all terrain vehicle accident in the snow in North Whitehall Township. In Bucks County, a pair of traffic accidents claimed the lives of four people. A 27-year-old male and a 26-year-old male were killed in a one car crash on the morning of the 29th on a snow covered road in Middletown Township. On the morning of the 30th, a 25-year-old male and his 31-year-old female passenger died in Bristol Township after the vehicle slid through a guard rail on Interstate 95, plunged down the embankment onto the shoulder of the Pennsylvania Turnpike. Another male and female passenger were injured in the same crash. There was a 25 vehicle crash overnight on Interstate 95 in Bucks County, but no additional serious injuries were reported. In Monroe County, a 57-year-old woman passenger died after the Sports Utility Vehicle she was a passenger in crashed into a car on Pennsylvania State Route 611 in Stroud Township.

The combination of the heavy wet snow and trees still with leaves on them caused nearly one million customers in Eastern Pennsylvania to lose power. For Pennsylvania, Power and Light, the 400,000 customers that lost power was the third worst outage in the utility's history. The utility had to use helicopters to survey the damage. Metropolitan Edison reported that about 285,000 of its customers lost power. PECO Energy reported that 250,000 of its customers lost power, its worst October outage ever. Bucks, Montgomery and Chester Counties were hit the hardest. Over 100 roads were closed in Eastern Pennsylvania because of the downed trees, 65 roads were still closed on November 1st and 34 roads were still closed on November 2nd. Most of them were in Berks and Lehigh Counties.

The Lehigh Valley was one of the hardest hit locations. Some schools and universities were closed through November 2nd. Two-thirds of the Borough of Emmaus lost power. Boil water advisories and shelters for pets were opened. Leaf collections were suspended. About 6,100 customers still did not have power as of November 3rd. In Berks County, hotels were solidly booked and some schools were not in session until November 3rd. In Bucks County, about 25 roads were blocked by fallen trees and tree limbs. The snow caused about 85 flights to be cancelled at the Philadelphia International Airport on the 29th.

Representative snowfall included 16.0 inches in Huffs Church (Berks County) and Springtown (Bucks County), 14.0 inches in Salisbury Township (Lehigh County), 13.5 inches in Summit Hill (Carbon County), 13.3 inches in Tobyhanna (Monroe County), 12.0 inches in Albrightsville (Carbon County), 11.5 inches in Bossardsville (Monroe County), 10.0 inches in Perkasie (Bucks County), 9.5 inches in Bushkill Township (Northampton County), 9.4 inches in Macungie (Lehigh County), 9.1 inches in Elverson (Chester County), 9.0 inches in Pocono Summit (Monroe County), 8.0 inches in Boyertown (Berks County) and Lehighton (Carbon County), 7.0 inches in Leesport (Berks County), 6.8 inches at the Lehigh Valley international Airport, 6.5 inches in Nazareth (Northampton County), 6.1 inches in Montgomeryville (Montgomery County), 6.0 inches in Trappe (Montgomery County), 5.2 inches in East Stroudsburg (Monroe County), 5.0 inches in Furlong (Bucks County) and Exton (Chester County), 4.0 inches in Wayne (Delaware County), 2.4 inches in Wynnewood (Montgomery County), 1.0 inch in Drexel Hill (Delaware County) and 0.3 inches at the Philadelphia International Airport.

The unprecedented winter storm was caused by an intensifying low pressure system that moved from Georgia on the evening of the 28th northeast to Cape Hatteras, North Carolina at 8 a.m. EDT on the 29th. From there it took a turn more toward the northnortheast and was off the Delmarva Peninsula at 2 p.m. EDT on the 29th. The low pressure system started moving to the northeast again and passed southeast of Montauk Point, New York at 8 p.m. EDT on the 29th and just southeast of Nantucket, Massachusetts at 2 a.m. EDT on the 30th. While the storm track would be ideal for a winter time snow, for an event like this to occur in late October, it needed assistance from a high pressure system that left dry air initially in place and made it easier for a process known as evaporational cooling to take place and make it cold enough for snow. Once the precipitation intensity became heavier, another process known as dynamical cooling (heat is removed from the air mass to melt the snow) more than compensated for the warm air that was moving in from the Atlantic Ocean.

The 6.8 inches of snow that fell at the Lehigh Valley International Airport was the heaviest snow to ever fall during the month of October more than tripling the previous record from 1925. This was only the fourth time since 1884 that measurable snow fell in Philadelphia in October and the first time since October 10, 1979.