After two days of severe weather that included deadly tornadoes, more violent storms will erupt over Nebraska and Iowa, while potentially damaging storms reach more than a thousand miles to the east to new ground in the mid-Atlantic.
There is a risk of tornadoes developing from isolated thunderstorms in portions of eastern Nebraska, western Iowa and southeastern South Dakota Wednesday evening.
According to Senior Meteorologist Bernie Rayno, "The setup is very similar to and in the same area as Monday evening, just not quite as volatile."
Areas from Lincoln and Omaha, Nebraska to Spencer, Iowa, and Sioux Falls, South Dakota, will need to keep an eye out for rapidly changing weather conditions late Wednesday and Wednesday evening.
"The storms will then transform into a large area of heavy rain, thunder and gusty winds farther to the north and east Wednesday night centered on southern Minnesota," Rayno said.
A boundary separating relatively cool air to the north from hot, muggy air to the south has been the focus of these powerful storms during the first part of this week.
This boundary will be in a similar location over the Plains and Midwest on Wednesday, compared to earlier in the week, thus setting the stage for incidents of flash flooding.
Individual thunderstorms may also continue to congeal into storm clusters.
The weather battle zone and risk of locally severe thunderstorms will sag southward in the Eastern states on Wednesday into Thursday.
The storms can bring frequent lightning strikes, hail, strong wind gusts and blinding downpours and also can cause disruptions to daily commutes, as well as other travel and outdoor activities.
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During Wednesday, the potential for gusty thunderstorms and localized severe weather will stretch across the Lower Peninsula of Michigan but can extend to northern Indiana, northern and central Ohio, southern and western Pennsylvania, northern Maryland and Delaware.
Cities in the path of potentially severe thunderstorms include Detroit; Toledo and Cleveland, Ohio; Fort Wayne, Indiana; Pittsburgh; Philadelphia; Wilmington, Delaware; and Atlantic City, New Jersey. The worst of the storms will likely stay south of New England and much of the New York City metro area.
The storms will mark an end of the extreme heat in part of the mid-Atlantic but much of the region, as well as the Midwest and South will remain in a zone of unsettled weather through the weekend.
If you can hear thunder, you are at risk of being struck by lightning.
Because of the speed of many of the storms and the potential volatility of the weather pattern, people spending an extended period of time outdoors will need to keep an eye out for rapidly changing conditions.
Spotty storms can also pop up away from the rim of the heat within the hot, humid air mass. Most of these storms will only affect a small area.
According to Meteorologist Mike Doll, "Recent rainfall has caused record flooding on the Big Sioux and Rock rivers in northwestern Iowa."
"Both of these rivers flow into the Missouri River, which could reach flood stage in Omaha, Nebraska, this weekend."
Thunderstorms producing tornadoes erupted for the second day in a row over portions of northern Nebraska and western Iowa on Tuesday evening.
Late in the week, a push of cooler air from eastern Canada will shove storms farther south along the East Coast, but the zone of storms will hold over the Midwest, Plains and South into the weekend. Rounds of severe weather will continue over portions of the Plains this weekend.
Matthew has become a hurricane in the Caribbean and may approach the U.S. during next week.
It will feel like an extended winter for those living from the northern Plains to the eastern U.S., as cold and snowy conditions last longer than normal.
Persistent downpours will raise the flood risk in part of the mid-Atlantic into Friday night, while rain will spread over the balance of the northeastern United States into the weekend.
Millions of people across the U.S. could be exposed to drinking water contaminated with chemicals from firefighting foam, according to a recent study.
The final day of September will bring a rare lunar event that hasn’t occurred since March of 2014, a Black Moon.
The holiday weekend will start on an unsettled note, but the weather should improve by Day of German Unity celebrations on Monday.
Johnstown, PA (1993)
Light snow in the city did not accumulate but up to 3" accumulated at the airport.
Goldsboro, NC (1999)
30" of rain in September.
U.S./Quebec border (1835)
Heavy snow; Hatley, P.Q. received 10 inches. Kelkenny, NH had 6 inches.