SUNDAY, DECEMBER 17, 2017
U.S. East Coast Winter Storm
1/25/2016 5:30:00 PM
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First Posting 1/25/2016 5:30:00 PM  
Summary
Posting Date: 1/25/2016 5:30:00 PM

The powerful storm that impacted 20 states in the eastern U.S., from January 22–24, delivered record-breaking snow totals, and produced hurricane-force wind gusts. Storm surges that exceeded those from Hurricane Sandy occurred in several areas. The storm shut down the nation’s capital and New York City over the weekend, forcing flight cancellations at major airports and causing power outages, roof collapses, and severe flooding in several states.

Record-Breaking Snow Levels

By Friday, the storm had already dropped several inches of snow along with freezing rain and sleet in the southeast, from Oklahoma to Tennessee and Kentucky. By the time the snow had stopped, eastern Kentucky had received 22 in (56 cm), and 8 in (20 cm) fell in Nashville, where “thundersnow” was also observed. The storm dropped 2 in (5 cm) in Mississippi and spawned two tornadoes that damaged homes and power lines in Lamar and Simpson counties.

More than a foot of snow fell in 20 states, with West Virginia receiving the most, at 42 in (107 cm) in Glengary. Philomont, Virginia, received 39 in (99 cm) while 38.3 in (97 cm) fell in Greencastle, Pennsylvania. Record snow totals were reported in several cities, including: 31.9 in (81 cm) in Allentown, Pennsylvania; 30.2 in (77 cm) in Harrisburg, Pennsylvania; 30.5 in (78 cm) at New York John F. Kennedy Airport; 29.2 in (74 cm) at the Baltimore-Washington International Airport, Maryland; and 27.9 in (71 cm) at both New York LaGuardia Airport and in Newark, New Jersey. The total snow depth of 26.8 in (68 cm) in New York’s Central Park was the second highest on record. Philadelphia and Washington, D.C. both received their fourth highest snow totals on record. Philadelphia collected 22.4 in (57 cm) and Washington, D.C. (at Reagan National Airport) received 17.8 in (45 cm).

snow_totals_air_cocorahs.png 

Total snow depths as of January 24 (Source: AIR and Community Collaborative Rain, Hail and Snow Network)

Fierce Winds and Damaging Storm Surges

The wind gusts from the storm reached hurricane strength in several areas early Saturday. Wind gusts of 85 mph (137 km/h) were recorded on Assateague Island, Maryland, which also reported sustained winds of 57 mph (92 km/h). Wind gusts of 75 mph (121 km/h) occurred on Block Island, Rhode Island, and Dewey Beach, Delaware. Sustained winds of 59 mph (95 km/h) occurred in Lewes, Delaware, while winds exceeding 55 mph (89 km/h) were recorded in other areas of Virginia and Delaware.

The storm coincided with a full moon and high tide, which increased the tidal effects of coastal flooding from Delaware to New Jersey. At Lewes, Delaware, a storm surge of 4 feet (1.2 m) above normal tide levels broke the water level on record for the area. One of the hardest-hit places was Cape May, New Jersey, where water levels reached 4 to 5 feet (1.2 to 1.5 m) above normal tide levels.

Reported Damage

The storm is responsible for at least 15 deaths. The accumulation of heavy, wet, snow has caused roof buckling in several states; large or long-span roofs that are flat or have a low pitch are particularly vulnerable. Roof collapses were reported in the Philadelphia metropolitan area, York County and other areas of Pennsylvania, as well as in Maryland, Virginia, New Jersey, Kentucky, and elsewhere. Some of the buildings that were damaged by roof collapses include a grocery store in New Jersey, a bowling center in Virginia, and other buildings with large roofs that are flat or have a low pitch.

The snow accumulation has also increased the risk of ice damming, as snow melts on the roofs of homes and refreezes. This has caused damage due to water leakage under roof shingles and over flashing, and has blocked gutters and drainage pipes. The weight of the dams can cause cracks and deformation in the wall/roof interface, allowing water to infiltrate ceilings and walls.

Flood damage has been reported in several residential and commercial buildings in Ocean City and other areas of Cape May. Damage is also reported in many areas of Long Beach Island. In several coastal areas, from Delaware to New Jersey, coastal flooding exceeded the levels seen during Hurricane Sandy in 2012. Streets in Ocean City, New Jersey, were flooded with three feet of standing water.

Disruption

By Friday, government offices across the southeast were closed along with schools and businesses. In Washington, the federal government offices were closed at noon on Friday. As of Monday, many areas, including Washington, are recovering with continued closures, transit disruptions, and delayed or canceled flights.

Travel has been greatly hampered due to treacherous roads and shuttered rail, bus, and subway systems. The Washington Metropolitan Area Transit Authority (Metro) suspended operations from Friday afternoon through Sunday, cancelling buses, rail, and the second-busiest subway system in the U.S. A travel ban was issued for New York City and the Southeastern Pennsylvania Transportation Authority halted bus, trolley, and rail service in Philadelphia. A massive seven-mile (11 km) backup on the Pennsylvania Turnpike blocked about 500 vehicles for nearly 24 hours, causing emergency situations due to lack of heat and food. Other motorists were stranded up to 19 hours along a vast stretch of Interstate 75, in Kentucky.

More than 12,000 flights were canceled at several major airports over the weekend, affecting flights internationally. Most of the cancellations were in North Carolina and Washington; in Philadelphia all flights through Saturday were canceled. Rail service was canceled or operated on a modified schedule.

Power outages were widespread as wind and heavy snow downed power lines. By early Friday afternoon, Duke Energy in North Carolina and Dominion Virginia both reported power outages. Through the weekend, power outages eventually affected about a quarter of a million people.

Exposure at Risk

The damage caused by snowfall is due primarily to the weight of the accumulated snowpack rather than to its depth. Therefore property damage is determined by snow load, which is the estimated weight of a snowpack. The snow load depends on the amount of water in the snow that is absorbed by the snowpack, increasing its density.

Heavy, dense snow can also down trees, causing damage to structures and automobiles, as well as downing power lines and causing power outages. Areas with long-duration power outages and lack of heat may experience frozen pipes.

Water equivalent snow totals in this storm would result in snow loads of 10 to 20 pounds per square foot on flat roofs, but this calculation does not account for snow drift, which can significantly increase loads. The risk of roof collapse is particularly acute for light metal, long-span roofs (such as on warehouses or hangars). Engineered structures must conform to high load tolerances and damage to these structures would be expected to be less. The roofs of marginally-engineered structures (such as small businesses and convenience stores) can collapse under large accumulations of snow, particularly if their roofs have not been well-maintained.

In the Mid-Atlantic and Appalachian Highlands, design snow loads are on the order of 15 to 20 pounds per square foot. Many old buildings may not meet the current code requirements, however, which can increase their vulnerability. Other building elements—porches, carports, awnings, and gutters—often do not receive any specific design attention and are vulnerable to heavy snow loads and significant ice dams. 

U.S. East Coast Winter Storm
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