Enhanced Risk of Severe Storms Across Illinois, Indiana, and Ohio on Thursday

On Thursday, there is a risk of thundershower activity in all of the shaded areas. The dark green represents a threat of severe storms while the yellow area reflects a greater risk. The area in orange is at greatest risk of seeing severe thunderstorms on Thursday. Image: SPC

According to the National Weather Service’s Storm Prediction Center (SPC), there is an enhanced risk of severe thunderstorms across portions of northern and central Illinois, Indiana, and portions of western Ohio for Thursday. On Friday, the active weather shifts to the Mid Atlantic but it doesn’t look like at this time there will be any widespread severe thunderstorm activity then and there.

Scattered severe thunderstorms are expected late Thursday afternoon and evening across parts of the Mid-Mississippi and Ohio Valleys. According to the SPC, very large hail, a few tornadoes, and severe wind gusts will be possible.

Several shortwave impulses are expected to migrate through initially zonal westerly flows across the Midwest and Great Lakes
region through late afternoon. tomorrow. Despite the low-amplitude nature of this environment, mid and upper-level flow will be somewhat strong, with most computer forecast guidance showing atmospheric ingredients ripe for severe weather overspreading the Mid-Mississippi, Ohio Valley, and Great Lakes region by afternoon. At the surface, a warm front will be oriented across central Iowa extending eastward along the Illinois/Wisconsin and Indiana/Ohio/Michigan border at midday. Then a weak surface low will propagate along this zone, with the front sagging southward as a cold front by late afternoon into the evening.

The SPC says that forecast soundings indicate capping could preclude warm sector convection for much of the daytime hours. In the absence of stronger large-scale ascent and surface cyclogenesis, the region will experience a broad warm advection regime, while low-level forcing along the front increases as it begins to march southward. With this set-up, supercells are expected and some may produce large to very large hail (2″+) .

“If any supercell can stay to the warm side of the surface front and maintain surface-based status, a tornado risk is also possible,” warns the SPC, adding that some strong tornadoes are possible.

With time, convection is expected to develop into a line or bowing segments given orientation of deep-shear vectors to the surface boundary. Because of this, damaging winds gusts are possible.

The severe risk should diminish with south and east extent during the nighttime hours as storms approach the Ohio River.