Severe thunderstorms could generate tornado threat around Great Lakes
A vigorous storm traveling eastward near the United States-Canada border will bring the risk of severe weather to parts of the Midwest into Wednesday evening and the eastern U.S. Thursday. The system could spawn tornadoes as it passes through portions of Michigan and the Canadian province of Ontario, AccuWeather meteorologists warn.
"The storm is unusually strong for summer standards and has an associated sharp dip in the jet stream that is often associated with severe weather," AccuWeather Senior Meteorologist Brett Anderson said.
The storm's greatest threat to lives and property through Tuesday night was from high winds. Since midnight local time Tuesday, the highest wind gusts in the region were reported in the North Dakota cities of Belcourt (75 mph), Manvel (71 mph) and Perth (70 mph).
Storms largely avoided the Chicago area entirely late Tuesday night and Wednesday morning, with just a few sprinkles. However, that may change significantly later Wednesday as the storm system pushes eastward.
As the storm system intersects with a surge of heat and high humidity coming up from the Southern states, the result will be an eruption of strong to severe thunderstorms Wednesday evening, according to Anderson.
"The primary risk during Wednesday afternoon and evening from southern Ontario to northern Kentucky will be from straight-line gusts and an associated line of thunderstorms, Anderson said. "But due to increasing wind shear with surging humidity, there is also the potential for a few tornadoes from the eastern part of the Lower Peninsula of Michigan to southwestern Ontario," he added.
Top wind gusts reported through Wednesday afternoon were in the metro area of Detroit (66 mph) as well as the cities of Oregon, Ohio (58 mph); Caseville, Michigan (56 mph) and Harbor View, Ohio (48 mph)
"These storms that occur farther to the north may initially form isolated discrete cells that are more likely to rotate and spawn tornadoes," Anderson said.
Wind shear is the change in speed and direction of breezes at different levels of the atmosphere above the ground. When winds shift direction and increase in speed from near the ground to a mile or two up in the atmosphere, individual thunderstorms can begin to rotate and may have more success at producing damaging wind gusts and tornadoes.
Major cities such as Detroit, Cleveland and London, Ontario, are forecast to be within the zone that could experience severe thunderstorms capable of spinning up a tornado.
Motorists from southwestern Ontario to Kentucky should be prepared for changing weather conditions that can produce sudden torrential rain and strong wind gusts that could produce near-zero visibility, meteorologists say. People spending time outdoors should seek shelter indoors at the first rumble of thunder to reduce the risk of being struck by lightning, experts warn.
"Mariners and small craft operators planning on going out on the Great Lakes should pay close attention to the weather, as storms may produce powerful wind gusts and frequent cloud-to-ground lightning," Anderson said. "Waters can transition to very rough and dangerous in a matter of minutes as the storms move in."
The storms are likely to lose intensity upon rolling eastward into western portions of New York, Pennsylvania, Maryland and West Virginia later Wednesday night.
On Thursday, the main storm system and most of the jet stream energy will pivot northeastward and reach into central and northern Quebec. AccuWeather meteorologists say some locally severe thunderstorms could also fire up from the St. Lawrence Valley to the Interstate 20 corridor through Alabama and Mississippi.
The main threats Thursday will be localized flash flooding and strong wind gusts that are forecast to reach 50-60 mph (80-95 km/h). Strong to severe storms could slice through Quebec City, Boston and Atlanta.
Any metro area in the East will be at risk for flash flooding Thursday in locations where storms rumble through. Abnormally dry to severe drought conditions persist in much of New England, despite downpours of late, according to the United States Drought Monitor.
The storms will offer a brief break from multiple days of heat in the Southeast and a building heat wave in the mid-Atlantic and southern New England.
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