INDIANAPOLIS, Indiana — Forecasters said the risk of strong to severe storms along the I-70 corridor was fading Sunday night, but a new round of building storm risk was expected to push through the region overnight, lasting through 3 AM ET. Radar current as of 9:57 PM ET on September 20 showed two separate storm zones on the move, one already active over Ohio and another building fast across Illinois and Indiana.
Two Storm Zones on the Move
As of the 9:57 PM ET radar update, two distinct areas of concern were flagged along the I-70 corridor.
- A Strong/Heavy Storm Risks Continuing zone stretched across central Ohio, including areas near Lima, Delaware, Newark, Columbus, Zanesville and Lancaster, where storms already active on radar were expected to keep producing locally heavy rain and gusty winds.
- A separate Building Storm Risks For Overnight zone stretched from around Springfield and Decatur, Illinois, through Taylorville, Charleston and Effingham, and into Terre Haute, Vincennes, Jasper and Olney in Indiana, where new storms were developing and expected to intensify overnight.
- A lighter band of Scattered Light Showers/Sprinkles was also moving across central Indiana near Lafayette and Danville, producing far less impactful weather than the two storm zones on either side of it.
Why the Severe Threat Is Fading But the Storm Risk Isn’t Over
Forecasters were clear that the primary risk for strong or severe storms, the kind capable of producing damaging wind gusts or large hail, had continued to decrease heading into the overnight hours. That does not mean the risk for storms ended altogether. Instead, the focus shifted toward heavy downpours capable of dropping large amounts of rain in a short period, a risk that does not require a storm to be technically severe to cause problems like localized flooding or ponding on roadways.
Storm Motion Overnight
Arrows on the radar graphic showed the building storm zone over Illinois and Indiana generally tracking east, while the storms already active over Ohio were also pushing east and southeast. That motion meant areas closer to Terre Haute and Vincennes were likely to see the newer building storms arrive first, with the risk continuing to shift eastward toward the already-active Ohio zone as the night progressed toward the 3 AM ET timeframe.
Areas Outside the Highlighted Risk Zones
Several larger cities visible on the radar map, including Fort Wayne, Toledo, Lexington and Louisville, sat outside both the continuing Ohio storm zone and the building Illinois-Indiana zone as of the 9:57 PM ET update. That did not rule out isolated showers reaching those areas overnight, but neither zone was specifically tracking toward them at the time this synopsis was issued.
What This Means for the I-70 Corridor Overnight
Communities strung along the I-70 corridor, from Terre Haute and Indianapolis in the west to Columbus, Zanesville and Lancaster in the east, were positioned to see multiple rounds of rain and storms move through before sunrise. Even without a specific severe thunderstorm warning in place at the time of this update, the combination of a continuing storm zone and a building storm zone meant overnight travel and outdoor plans along the corridor carried real risk of sudden downpours and reduced visibility.
What Residents Along the Corridor Should Do
- Keep a phone nearby with weather alerts turned on overnight, since new warnings can be issued quickly as the building storm zone intensifies.
- Avoid driving through flooded roadways, since heavy downpour risk can create dangerous ponding even without a severe thunderstorm warning in effect.
- Do not assume the threat has passed simply because the primary severe risk was decreasing, since the storm and downpour risk was expected to continue through 3 AM ET.
- Anyone traveling the I-70 corridor overnight, especially between Terre Haute and Columbus, should expect the possibility of sudden heavy rain and reduced visibility at any point along the route.
- Check the latest radar before heading out, since the building storm zone was still developing at the time of this update and its exact path overnight was not yet finalized.
