US, Canada: Major winter storm to impact the eastern US and Canada through at least Dec. 17 /update 2

Event

A major winter storm will continue to bring heavy snowfall, ice, and strong winds to portions of the Mid-Atlantic and Northeast regions of the US, as well as far southeastern Canada, through at least Dec. 17. The affected areas in the US include the Blue Ridge and Allegany mountain areas from western Virginia northward into western Maryland; central and northern Maryland, northern Delaware, Pennsylvania, northern and central New Jersey, and New York, as well as most of southern and central New England. Impact areas in Canada include far southern Ontario, southern New Brunswick, Prince Edward Island, and Nova Scotia. As of the late afternoon of Dec. 16, snow has arrived in southeastern New York, western Connecticut, northern and central New Jersey, Pennsylvania, western and central Maryland, and eastern West Virginia. Sleet and freezing rain are being observed near Interstate 95 in northern Virginia and central and eastern Maryland, northern Delaware, and southwestern New Jersey; rain is falling farther south and east.

Forecast models indicate that, by the evening of Dec. 16, snow will become heavy across central Pennsylvania, northern Maryland, and northeastern West Virginia, while light-to-moderate snow falls in eastern Pennsylvania, northern and central New Jersey, western Pennsylvania, southeastern New York, and southwestern Connecticut. Mixed precipitation will continue to fall near the I-95 corridor from southern New Jersey to northern Virginia while rain falls farther south and east. Heavy snowfall will continue across Pennsylvania and Maryland, spreading toward northern New Jersey, southeastern New York, and Connecticut overnight, eventually arriving in Rhode Island, Massachusetts, Vermont, and New Hampshire. The snow will become heavy across southern New England early Dec. 17 as the system departs the Mid-Atlantic region. Snow will arrive in Atlantic Canada by the afternoon of Dec. 17 and persist through early Dec. 18.

Some uncertainty remains in the forecast and projected snow and ice accumulations are subject to changes over the coming hours.

Government Advisories
As of the evening of Dec. 16, the US National Weather Service (NWS) has issued winter storm warnings for eastern West Virginia, northern and western Virginia, northern and western Maryland, all but northwestern Pennsylvania, northern New Jersey, central and southeastern New York, Connecticut, Rhode Island, Massachusetts, southern Vermont, southern New Hampshire, and southern Maine. Additionally, Environment Canada maintains snowfall warnings for portions of Nova Scotia. Authorities will likely issue new alerts or update/rescind existing advisories as the winter storm transits the region over the coming days.

In advance of the storm, states of emergencies have been declared in Pennsylvania, Virginia, and New Jersey.

Hazardous Conditions
Forecast models indicate that widespread accumulations of 30-50 cm (12-20 inches) will occur in an area encompassing northeastern West Virginia, central and northeastern Pennsylvania, northwestern New Jersey central and interior southeastern New York, western Massachusetts, and northern and central Connecticut. Locally higher amounts of up to 76 cm (30 inches) are possible in the hardest-hit areas, including central Pennsylvania. 15-30 cm (6-12 inches) are expected in western Pennsylvania, southeastern Pennsylvania, central and northern New Jersey, southern Maine, southern Vermont, southern New Hampshire, southern Connecticut, Rhode Island, and eastern Massachusetts in the US, as well as Nova Scotia, New Brunswick, and Prince Edward Island in Canada; this area includes Boston and New York City. Lower amounts of 7.5-15 cm (3-6 inches) are expected farther southeast, including Long Island, central New Jersey, far southeastern Pennsylvania, western New York, eastern Ohio, central Maryland, and northern Virginia. This area includes Philadelphia. Little to no snow is expected farther south and east where the snow will mix with sleet and rain for prolonged periods. However, there is still some uncertainty associated with snowfall totals due to sleet and freezing rain mixing with the snow for locations near the I-95 corridor including the New York City, Philadelphia, Baltimore, and Washington metropolitan areas. Additionally, ice accumulations of 0.25-0.64 cm (0.1-0.25 inches) are expected in the Shenandoah Valley of Virginia and central Maryland.

In addition to the heavy snow, strong wind gusts could lead to periods of blowing and drifting snow. Blizzard conditions are possible, especially in areas closer to the coast. Snowfall rates may reach 7.5 cm (3 inches) per hour in the heaviest bands.

Transport
The inclement weather will likely cause widespread and prolonged ground and air transport disruptions across the affected area through at least Dec. 17. Weather conditions should gradually improve from southwest to northeast Dec. 17. Traffic and commercial trucking delays and closures are expected along regional highways including the I-68, I-70, I-76, I-78, I-79, I-80, I-81, I-83, I-84, I-86, I-87, I-88, I-89, I-90, I-91, I-93, I-95, and I-99 corridors in the US, as well as the Trans-Canada Highway. Difficult and potentially dangerous driving conditions are also likely on secondary and rural roadways in the affected states as maintenance crews prioritize clearing major routes. Authorities could close stretches of a highway if driving conditions become too hazardous. Gusty winds may threaten to topple high-profile vehicles throughout the affected area. Heavy wet snow and strong winds could bring down power lines and trees with foliage. Flight delays and cancellations are likely due to ground stops and deicing operations at regional airports including those serving Baltimore (BWI), New York City (JFK, LGA), Newark (EWR), Philadelphia (PHL), Pittsburgh (PIT), Albany (ALB), and Boston (BOS).

Advice

Monitor local media for updated weather information. Verify road conditions before driving in areas where heavy snowfall is forecast. Allow extra time to reach destinations in these areas and carry an emergency kit and warm clothes if driving is necessary, especially on secondary or rural routes that could become impassable. Plan accordingly for delivery delays if routing shipments by truck through the affected area through at least Dec. 17. Confirm flights. Charge battery-powered devices in the case of prolonged electricity outages.

Resources

National Weather Service
US Road Conditions
Meteorological Service of Canada