Strong winds, heavy snow, flooding predicted for east coast

Eastern Canada and the U.S. were getting heavy snow Friday morning, with AIR Worldwide warning of the possibility of collapsing roofs, power outages and frozen pipes in the U.S. northeast.

 “The combination of heavy snow and intense winds means that drifting snow could be a problem over the watch area, increasing the possibility of roof collapse for light metal structures with large roof areas,” AIR Worldwide stated in an alert on its website.

The U.S. National Weather Service was calling for an accumulation of two to four inches (five to 10 cm) of snow during the day and up to 20 inches (about half a metre) of snow Friday night in Boston. The wind in Boston was forecast at 22 to 29 mph (35 to 46 kph), with gusts of up to 55 mph (88 kph).

 Meanwhile, Boston-based AIR Worldwide, a Verisk Analytics Inc. unit that makes catastrophe modelling software, noted design snow loads in the U.S. northeast are “on the order of” 20 to 50 pounds per square foot, adding 10 to 20 inches of snow can produce loads of about 15 to 30 psf on flat roofs.

 “Other building elements-porches, carports, awnings, and gutters-which often do not receive any specific design attention, are similarly vulnerable under the forecast conditions,” AIR Worldwide stated. “It should also be noted that there are many old buildings in the Northeast that may not meet the current code requirements, which may further increase the total damage.”

According to the National Weather Service, as of 3:00 Friday morning, a low pressure system was beginning to intensify as it moved northeastward off the coast of North Carolina. Another low pressure system was moving east across northwestern Ohio.

“A Texas low has tracked northeast to Ohio and will follow a path over Lake Erie into Western New York State later today,” according to the Environment Canada website. “The storm centre will move away tonight and merge with another winter storm forecast to affect parts of New England and the Maritimes.”

As of 10:51 Friday morning, Environment Canada was forecasting that the system off the North Carolina coast will track south of Nova Scotia Saturday morning, bringing heavy snow and winds gusts of 80 to 100 km/h in the province Friday night and into Saturday.

“Total snowfall amounts of 20 to 30 centimetres are expected throughout the province however there is a possibility of 30 to 40 centimetres over inland areas,” Environment Canada said of Nova Scotia. “The snow will become mixed with ice pellets along the south shore Saturday morning.”

Environment Canada is also predicting higher water levels and pounding surf along the south shore of Nova Scotia from Halifax County to Shelburne County in the southwest.

“There is a risk of some coastal flooding due to the very rough sea and the resulting elevated water levels especially around high tide Saturday morning,” Environment Canada said in its warning for Yarmouth County.

Further west, Environment Canada issued a blowing snow warning for Montreal. In Ontario, the weather service forecast 15 to 25 cm in Toronto, and 25 cm for the suburbs southwest and west of Toronto, as well as Hamilton, London, Sarnia and the Kitchener-Waterloo-Cambridge area.

“The heaviest snow will occur during the morning rush hour along the highway 401 corridor from London across the Waterloo region and the Greater Toronto area,” Environment Canada stated. “Heavy snow will spread quickly east during the day to affect Kingston through Brockville to Cornwall. Strong and gusty northeasterly winds will whip up the freshly fallen snow and result in very low visibility at times in blowing snow.”

Blizzard warnings were also in effect for Saint John, N.B. while St. John’s, Nfld. and the Avalon Peninsula were under a winter storm watch.

“Further complicating the scenario is the possibility that rain and sleet may fall as mixed precipitation in southeast Massachusetts and Rhode Island,” AIR Worldwide scientist Tim Doggett stated in a press release. “If this happens, then there will be more weight added to the snow, and the damage potential will increase. The accumulated snow, together with winds, may also cause downed trees across the region, causing damage to structures and automobiles. 

Doggett also warned of down power lines in the eastern U.S. suggesting a lack of heat may cause pipes to freeze.