Canada, US: Adverse weather forecast across parts of southeastern Canada and the eastern and northeastern US through at least early Dec. 21

Severe weather is forecast over parts of southeastern Canada and the eastern and northeastern US through at least early Dec. 21. A strong storm system will move northward from the Mid-Atlantic in the US into the northeastern US and southeastern Canada Dec. 18-19, bringing heavy rainfall, strong winds, and possible thunderstorms across the region over the coming days. Rainfall totals of over 10 cm (4 inches) are possible across parts of the affected area, as well as winds gusting over 100 kph (62 mph). Strong winds will generate rough seas in coastal areas. Heavy downpours could trigger flooding in low-lying areas, and strong winds could cause property damage and power outages.

As of early Dec. 18, Environment Canada has issued red rainfall warnings (the highest level on a three-tier scale) across parts of New Brunswick, western Newfoundland and Labrador, Nova Scotia, and eastern and southern Quebec. Red wind warnings are in place for parts of southern New Brunswick, eastern and southern Newfoundland and Labrador, Nova Scotia, Prince Edward Island, and eastern Quebec, as well as storm surge warnings for parts of southern Nova Scotia and eastern Quebec. A special weather statement for strong winds and heavy downpours is in place for parts of northern Newfoundland and one for heavy rainfall in parts of southeastern Ontario.

The US National Weather Service (NWS) has issued flood warnings, watches, and advisories across parts of central and eastern North Carolina, eastern Virginia, Maryland, Delaware, New Jersey, eastern Pennsylvania, central, eastern, and southern New York, Vermont, and central New Hampshire. Flash flood warnings are in place for parts of eastern Virginia and southeastern Maryland early Dec. 18. High wind warnings and advisories have been issued across much of the Mid-Atlantic and northeastern US. Coastal flood and high surf warnings and advisories are in place across many eastern and northeastern coastal areas, as well as marine warnings for strong winds and rough seas for offshore coastal waters.

The NWS's Weather Prediction Service has warned of a Slight Risk (level 2 on a four-tier scale) of excessive rainfall for coastal and adjacent inland areas from North Carolina northward to New England through early Dec. 18 and from New Jersey through Maine Dec. 18-19. The NWS's Storm Prediction Center has warned of a Slight Risk (level 2 on a five-tier scale) for parts of eastern North Carolina early Dec. 18.

Officials could update and possibly extend the coverage of weather alerts over the coming hours, including possibly issuing tornado warnings.

The severe weather could contribute to transport disruptions throughout the region. Floodwaters and debris flows may render some bridges, rail networks, or roadways impassable, impacting overland travel in and around affected areas. Ponding on road surfaces could cause hazardous driving conditions on regional highways. Authorities could temporarily close some low-lying routes that become inundated by floodwaters.

Severe weather may trigger flight delays and cancellations at airports across the affected region. Flooding could block regional rail lines; freight and passenger train delays and cancellations are possible in areas with heavy rainfall and potential track inundation.

Localized business disruptions could occur in flood- or storm-hit areas; some businesses might not operate at full capacity because of damage to facilities, possible evacuations, and some employees' inability to reach work sites. Strong winds could also cause power outages.