US, Canada: Heavy rain and storms could lead to possible flooding and potential transport disruptions in the eastern US and Canada, Dec. 5-6.

Event

A rapidly strengthening, low-pressure system will bring heavy rain and thunderstorms to portions of the eastern US and southeastern Canada, Dec. 5-6. The affected areas include northeastern South Carolina, eastern North Carolina, eastern Virginia, central and eastern Maryland, the District of Columbia, Delaware, far southeastern Pennsylvania, central and southern New Jersey, Long Island, New York, southeastern Connecticut, Rhode Island, eastern Massachusetts, Down East Maine, and New Brunswick, Canada. Forecast models initial rounds of rain will develop in North Carolina, South Carolina, and Virginia late Dec. 4 before spreading eastward toward the District of Columbia, Maryland, and Delaware early Dec. 5. The rain will become heavy across the Mid-Atlantic region early Dec. 5. The heavy rainfall will quickly spread northeastward toward New Jersey, southeastern Pennsylvania, and Long Island, New York by late morning Dec. 5. Connecticut, Rhode Island, and Massachusetts will be impacted beginning midday or early afternoon Dec. 5. Down East Maine and New Brunswick, Canada will experience heavy rain beginning late Dec. 5. The storm system will fully depart the Mid-Atlantic region of the US by the afternoon of Dec. 5 and New England and southeastern Canada by the afternoon of Dec. 6. Some uncertainty remains in the forecast track and changes could occur over the coming hours.

Hazardous Conditions
The storms will be capable of producing heavy downpours and strong winds, especially areas closer to the coast. Rainfall totals of 5-15 cm (2-6 inches) are expected in the hardest-hit areas, including New Brunswick, Canada, Down East Maine, southeastern Massachusetts, eastern Long Island, New York, and coastal locations in Delaware and Maryland. 2.5-7.5 cm (1-3 inches) are expected across the rest of the affected area with lower totals farther north and west away from the coast. Should sustained heavy rainfall occur, it could trigger flooding in low-lying communities near rivers, streams, and creeks. Urban flooding is also possible in developed areas with easily overwhelmed or a lack of stormwater drainage systems if severe storms are present. Disruptions to electricity and telecommunications services are possible if severe weather impacts utility networks.

In addition to heavy rainfall and possible flooding, there could also be severe thunderstorms in portions of the Mid-Atlantic region, especially in eastern North Carolina and southeastern Virginia. Storms could contain heavy downpours, damaging winds, and even a few tornadoes in that region. Additionally, the rain may changeover to heavy, wet snow in portions of New England, including northeastern Connecticut, northern Rhode Island, interior southeastern Massachusetts, Maine, and New Brunswick, which could lead to further disruptions,

Transport
The severe weather may contribute to localized ground and rail transport disruptions throughout the affected area. Traffic and commercial trucking delays might occur along regional highways, including the I-40, I-64, I-66, I-70, I-76, I-85, I-90, I-93, I-95, and I-97 corridors in the US, as well as the Trans-Canada Highway and Vanier Highway in Canada, Strong winds might also pose a hazard to high-profile vehicles. Hazardous weather conditions might cause sporadic flight delays at regional airports, including, but not limited to, those serving Raleigh (RDU), Richmond (RIC), Washington (DCA, IAD), Baltimore (BWI), Philadelphia (PHL), New York City (JFK, LGA), Providence (PVD), Boston (BOS), Portland (PWM), and Moncton (YQM). If flooding occurs, regional rail lines could be blocked.

Advice

Out of an abundance of caution, confirm flights, seek updated information on weather and road conditions before driving or routing shipments through areas where severe weather is forecast, and plan for potential freight delivery delays. Do not attempt to drive through flooded areas. Review contingency plans and be prepared to move quickly to shelter if tornado warnings are issued. Charge battery-powered devices in the case of electricity outages.

Resources

National Weather Service (NWS)
US Road Conditions
Meteorological Service of Canada