AccuWeather meteorologists warn that as the cold front gains momentum, severe thunderstorms, many with gusty winds, will break out and roll from the eastern Great Lakes, Ohio and central Mississippi Valleys into the Appalachians and Atlantic Ocean along the coast, continuing into Wednesday and beyond.
As the storm approaches and passes through major metropolitan areas, it could trigger regional power outages and cause significant travel delays. Tree and property damage is possible in some communities.
Severe storms have wreaked havoc on parts of the interior Midwest and Northeast in recent days. Monday night alone saw hundreds of high wind and wind damage events from Iowa to Illinois and Indiana, with large, severe thunderstorms covering hundreds of miles and spawning multiple tornadoes in the Chicago area. Report.
AccuWeather meteorologists believe the complex meets the National Weather Service's definition of a derecho, which is sustained strong gusts (58 mph or greater) over a distance of at least 400 miles. According to poweroutage.us, nearly 300,000 utility customers were temporarily without power from Iowa to Illinois and Indiana after Tuesday's storm.
Although the conditions that produce severe thunderstorm complexes are changing, that doesn't mean storms won't be severe at local and regional levels.
“The front is moving into an area of very hot and humid air, so it won't take much to produce severe gusty thunderstorms, at least in many locations,” said AccuWeather Chief Airborne Meteorologist Bernie Rayno.
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Any metro area experiencing sustained heavy downpours is likely to experience brief urban flooding. Toronto was hit by several hours of heavy rain on Tuesday morning, causing some city streets to look like rivers and flooding several vehicles.
Another heavy rain hit Tuesday in east-central Missouri and west-central Illinois. Areas around St. Louis received 1 to 3 inches of rainfall. Higher amounts occur locally and push small streams out of their banks. A dam near Nashville, Illinois, southeast of St. Louis, is in danger of failure.
As the cold front continues to approach midweek, the chance of severe thunderstorms will also increase.
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The threat of severe weather on Wednesday is expected to extend from New Brunswick south into the Carolinas and northern Georgia and then west into eastern parts of Kansas and Oklahoma. Severe thunderstorms are expected in parts of the region, with moderate risk of severe weather along Interstate 95 from southern Maine to northern Virginia and further west in Virginia. Moderate risk means multiple severe thunderstorms are possible.
Similar to Tuesday, the main threat to life and property will come from strong wind gusts and frequent lightning strikes. However, heavy downpours can also hamper travel.
AccuWeather Local StormMax™ wind gusts for Wednesday's storm are 75 mph.
The overall intensity of severe weather is likely to weaken and become more sporadic on Thursday. However, there will be at least some risk of locally damaging thunderstorms, including high winds and heavy downpours, focused not only on the Carolinas but also across much of Georgia and central and southern Virginia.
Isolated severe gusty thunderstorms may also extend westward into parts of the lower Mississippi Valley on Thursday.
As storms roll through Southeastern states from Thursday into the weekend and the cold front is expected to stall, flash flooding events could increase as beneficial rainfall becomes more problematic in drought-stricken areas.
“Rainfall amounts of 1-3 inches are possible this weekend into early next week, but if the downpours continue, totals of 6 inches or more are possible,” AccuWeather Meteorologist Elizabeth Danco said.
Some severe downpours could bring 1-2 inches of rain per hour, enough to cause urban flooding problems.
Even with heavy rain becoming a major issue for outdoor plans, some storms could be strong enough to trigger locally damaging wind gusts in southeastern states during the afternoon and evening hours.
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