Early March storm to raise flood risk in Northeast US, southern Canada
Temperatures will climb, rain will pour down and a lot of snow will melt in the northeastern United States and southeastern Canada, which will raise the risk of major flooding in the first week of March.
After a cold start to March in the Northeast, temperatures will rise just in time for thunderstorms and rain to arrive.
A major storm will swing from the south-central United States to southeastern Canada during the first week of March and unleash drenching rain as temperatures climb. Major flooding may unfold during the thaw and could be made worse in areas where deep snow from recent winter storms melts rapidly, AccuWeather meteorologists warn.
Any time there is a deep snowpack in spring, there is the potential for a quick meltdown that can lead to flooding. In the high elevations of the West, this tends to be rare. Where deep snow lays in low or intermediate elevations, especially in the humid regions of the East, the stakes are raised significantly in situations where storms have access to Gulf and Atlantic moisture.
FILE - This March 10, 1992 aerial photo shows floodwaters from the North Branch of the Winooski River in downtown Montpelier, Vt. (AP Photo/Jim Cole, File)
The area from northern New England and upstate New York to southern portions of Quebec and Ontario can experience quick meltdowns and flooding. Unfortunately, there is the potential for rapidly melting snow combined with rain during the middle of this week.
As the big storm tracks from the central Great Lakes and into southeastern Canada Wednesday, it will tap Gulf and Atlantic moisture in the form of drenching rain and pull warm air northward.
The quick flip to warmer air sent temperatures well into the 30s, 40s, and 50s F on Tuesday, raising the snowpack's temperature.
Snow cover is currently deep in portions of central and northern New York, northern New England, southern Quebec and southeastern Ontario, ranging from 1 to 3 feet, with locally greater amounts, AccuWeather Senior Meteorologist Joe Lundberg said.
In some areas, the snow cover contains 5 to 10 inches of water.
"With the potential for 1-2 inches of rain to fall from the upcoming storm, combined with melting snow, that can add several to many more inches of water being released, runoff will accelerate into small streams and progressively larger rivers, and can lead to major flooding," Lundberg explained.
Flooding on small streams will be rapid. The surging water may take a couple of days to reach some of the larger rivers in the region, such as the Mohawk, Connecticut and Ottawa.
"Where some streams and rivers are frozen, ice jam flooding may also develop and become a serious concern," Lundberg added.
Residents in Eastlake, Ohio, are still reeling from the flooding and damage caused by an ice jam in the Chagrin River.
Some communities have mountainous piles of snow along streets and highways, and some are blocking storm drains. As a result, significant urban flooding is possible, including in the metro areas of Montreal, Quebec City, Toronto, and Ottawa in Canada, as well as Burlington, Vermont; Plattsburgh, New York; and Caribou, Maine.
Enough rain may pour down to lead to incidents of urban flooding throughout New England, the mid-Atlantic, the central Appalachians and the Great Lakes region. This includes the major metro areas of Boston, New York City, Philadelphia, Washington, D.C., and Pittsburgh in the Northeast. Runoff from an inch of rain can also lead to a moderate rise in small streams.
Farther southwest, there is concern that enough rain may fall on portions of Kentucky, Tennessee, Ohio, Indiana and West Virginia to bring renewed flooding. Some stream and river levels remain high from the deadly deluge that occurred in mid-February.
Travelers should expect delays to increase into Wednesday as the rain arrives and areas of fog develop. River flooding, mainly along the secondary rivers in the St. Lawrence Valley, may take several days to a week to recede.
Factors that could limit runoff from the storm include a storm that tracks farther south, which would limit the amount of warming in part of the critical deep snowpack zone. Lighter or more sporadic rain than anticipated could also help mitigate the flooding potential. It is also possible that a wedge of cold air may hang on during most of the storm, which could keep the snowpack temperature lower for a longer period of time.
Additional storms, some with drenching rain, are forecast as March continues, so periodic problems with surging stream and river levels may occur in the coming weeks.
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