Monday, August 21, 2017

Severe Storms Threaten Plains, Midwest and Northeast Early This Week

Brian Donegan
Published: August 21,2017

Severe thunderstorms with damaging winds and large hail are possible early this week from the Plains and Midwest into the Northeast.
(MORE: Tornado Central)

Current Radar, Watches and Warnings
Strong winds aloft, associated with a maximum in the jet stream, will be in place over the Plains and Midwest into Monday evening, while a potent late-August cold front sweeps through at the surface. A warm and humid airmass will also engulf the regions, providing additional fuel to the atmosphere which will aid in thunderstorm formation.
By Tuesday, the jet stream maximum will shift toward the Ohio Valley and interior Northeast, where thunderstorms should flare up during the afternoon and evening hours ahead of the potent cold front. Hot and humid conditions will also be in place in those regions, which will increase the risk for severe weather due to extra moisture in the atmosphere.
(MORE: View National Interactive Radar Map | Difference Between a Watch and a Warning)
Below is our latest forecast thinking on the timing and magnitude of the severe threats early this week.

Severe Weather Forecast

Into Monday Evening
  • Forecast: Scattered severe thunderstorms are forecast to impact parts of the mid-Missouri Valley east-northeastward into the mid- and upper Mississippi Valley into the evening.
  • Threats: Damaging wind gusts and large hail are the main threats, but an isolated tornado cannot be ruled out. Flash flooding is also possible, especially where storms stall or move slowly over the same areas for a period of an hour or more.
  • Cities: Madison, Wisconsin | Des Moines, Iowa | Omaha, Nebraska

Thunderstorm Forecast into Monday Evening
  • Forecast: Severe thunderstorms are possible across much of upstate New York and Vermont southwestward into central and western Pennsylvania and the Ohio Valley, as well as parts of the mid-Mississippi Valley, during the afternoon and evening. Showers and storms could reach parts of the heavily-populated Interstate 95 Northeast corridor later Tuesday evening or overnight, but the risk for severe weather will be minimal as the storms weaken after sunset.
  • Threats: Damaging wind gusts are the primary threat, though large hail and an isolated tornado can't be ruled out. Flash flooding is also possible, especially where storms stall or move slowly over the same areas for a period of an hour or more.
  • Cities: Buffalo, New York | Pittsburgh | Cleveland | Cincinnati | Indianapolis

Tuesday's Thunderstorm Forecast
Following the early-week severe weather, a much cooler airmass will build in behind the cold front over the Plains, Midwest and Northeast for the second half of the week.
Highs will generally be 5 to 10 degrees below average for late August, as the muggy 80s and lower 90s are replaced by temperatures in the 70s and lower 80s.
(MAPS: 10-Day Forecast High/Low Temperatures)

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