TL;DR

The NOAA Storm Prediction Center has issued a Slight Risk for severe thunderstorms from the southern Great Lakes into the Mid-Atlantic states on Friday, September 4, 2026. Damaging wind gusts are the primary threat as organized thunderstorm clusters move southeastward through the Ohio Valley and into the Mid-Atlantic this afternoon and evening. Central and eastern Ohio face the greatest potential for damaging gusts where buoyancy and wind shear overlap most favorably.

Where is the highest risk today?

The Slight Risk corridor stretches from the southern Great Lakes through the Ohio Valley and into the Mid-Atlantic states. According to the Storm Prediction Center's Day 1 outlook, "a couple of organized clusters of thunderstorms may develop across the southern Great Lakes and mid/upper Ohio Valley today through tonight, accompanied by the risk for damaging wind gusts."

The greatest potential for damaging gusts exists across central and eastern Ohio, where the best overlap between atmospheric buoyancy and deep-layer wind shear is forecast. The threat extends eastward into Pennsylvania, West Virginia, Maryland, Virginia, and the broader Mid-Atlantic region through this evening.

Cities in or near the Slight Risk area include:

What's driving today's severe weather?

Early Friday morning, a large cluster of showers and thunderstorms was already underway from southern Wisconsin into southern Lower Michigan. This cluster formed overnight due to warm-air advection across Minnesota and Wisconsin and is forecast to continue moving southeastward throughout the day.

The atmospheric setup features deep upper-level ridging covering most of the eastern United States, with a belt of enhanced mid-level flow arcing from the central Rockies through the northern Plains and into the Upper Midwest and Northeast. A weak surface front extends from southern New England through southern New York, central Lower Michigan, and central Wisconsin to a weak low over southern Minnesota.

As the morning thunderstorm cluster pushes southeastward, it will encounter a diurnally destabilized airmass—meaning the atmosphere will become increasingly unstable as daytime heating takes hold. Upper 60s to low 70s dewpoints combined with afternoon temperatures from the mid-80s to mid-90s will support moderate to strong buoyancy, the atmospheric fuel for thunderstorms.

SPC forecasters note that "reintensification and/or new development is anticipated as the ongoing cluster continues southeastward." Bowing line segments—curved sections of a squall line that produce concentrated wind damage—are expected to be the predominant storm mode.

When will storms arrive?

The ongoing cluster over the southern Great Lakes will continue moving southeastward through the morning and into the afternoon. Central and eastern Ohio will see the greatest severe weather potential during the afternoon hours as the cluster moves through the region.

For the Mid-Atlantic, the threat window opens this afternoon and continues into the evening. SPC notes that "more widely scattered strong thunderstorms east of the Blue Ridge may also pose potential for damaging wind gusts this afternoon and evening."

Timing specifics will depend on how quickly the morning cluster reorganizes and whether new development occurs along and ahead of the main line. Residents across the risk area should monitor radar and local National Weather Service forecasts throughout the afternoon and evening.

What hazards to expect

Damaging wind gusts are the primary threat today. The storm mode—bowing line segments within organized clusters—is particularly efficient at producing concentrated areas of straight-line wind damage.

In the Mid-Atlantic, vertical wind shear will be weaker than farther north, but the airmass will be exceptionally warm and moist. Precipitable water values—a measure of atmospheric moisture—will range from 1.8 to 2 inches, supporting very heavy rainfall rates.

Hail and isolated tornadoes are not the focus of today's outlook, though any organized thunderstorm can produce lightning and localized flash flooding given the high moisture content.

Yesterday's severe weather recap

The past 24 hours brought 348 wind reports and 26 hail reports across a broad swath of the Upper Midwest, Great Lakes, and Mid-Atlantic. No tornadoes were reported.

The largest hail—2.30 inches in diameter, roughly the size of a baseball—fell in two locations in Minnesota: 3 miles west-northwest of Elbow Lake and 6 miles south of Naytahwaush. Both reports came from broadcast media sharing photos of hailstones near Tulaby Lake around 2123 UTC on September 3.

Wind damage was widespread, with 348 reports spanning 15 states. Pennsylvania, Michigan, and North Dakota saw the bulk of the reports, including numerous downed trees and power lines. Washington County Emergency Management in Wisconsin reported "widespread tree damage across Richfield, including uprooted trees" with estimated winds of 60 mph.

The activity was driven by similar atmospheric dynamics to what's expected today—organized thunderstorm clusters moving through a moist, unstable airmass.

What to do now

If you're in the Slight Risk area, take these steps:

  • Monitor radar and warnings. Download a reliable weather app or bookmark your local NWS office's page. VORTEX is a free web app at vortexintel.app that monitors severe weather nationwide.
  • Secure outdoor items. Damaging wind gusts can turn patio furniture, trampolines, and trash cans into projectiles.
  • Identify your safe spot. If a severe thunderstorm warning is issued for your location, move to an interior room on the lowest floor, away from windows.
  • Charge devices now. Widespread wind damage can lead to extended power outages.
  • Avoid travel during peak storm hours if possible, especially across central and eastern Ohio this afternoon.

Tomorrow's outlook

SPC's Day 2 outlook maintains a Slight Risk across portions of the Ohio Valley, Mid-Atlantic, and into the Southeast for Saturday, September 5. The threat will shift eastward as the upper-level pattern evolves, with continued potential for damaging wind gusts. Day 3 shows a Marginal Risk across the Northern Plains, Midwest, and Southeast for Sunday.

The active early-September pattern is expected to continue into next week as moisture and instability remain in place across much of the eastern United States.

VORTEX is a free web app at vortexintel.app that monitors severe weather nationwide. Pro ($4.99/month) places phone calls to your phone when a tornado or flash flood warning is issued for a location you care about — calls can ring through Do Not Disturb once you enable Emergency Bypass for the number, unlike most third-party app notifications.