March 10, 2026

A potent warm front setup was shaping up for Tuesday, March 10 across northern Illinois into Indiana. Models showed the front retreating and reinforced by a strong lake breeze coming off Lake Michigan that would further push the boundary south. I was worried cells would cross the boundary too quickly or get undercut by it, while the open warm sector did not have ideal hodographs. Still, any cell tracking near or along the front would pose a tornado threat given moderate instability in the strongly sheared environment. I noted over 2500 J/kg of MUCAPE north of the warm front as well, and with low freezing levels, anticipated these cells would be prolific hailers. Without extreme dynamic forcing or extreme instability, I wasn't anticipating huge hail, however. Convective Allowing Models showed a two round play, with an early afternoon round firing in the warm sector and tracking along the warm front toward the IL/IN border. I expected a cell in this environment to be a tornado producer as it approached the warm front, but then later transition into a tornado-warned HP hailer as it moved into Indiana where the lake breeze boundary was focused and instability levels were lower. A round two was expected near the cold front closer to sunset near the Illinois River/Peoria. That looked like the more photogenic play to me, with evening light on cells in a favorable environment. The initial plan was to get on an early cell, chase it until it transitioned HP, and then fall back to the cold front if we could make it back there in time before dark or cells congealed.

Jennifer Brindley Ubl was in for this chase, and it was great to have my regular partner back. We met up in La Salle where 80 and 39 intersect, and stashed her car at a truck stop before dropping south of the river to monitor conditions. We were sitting right on the warm front, and to me, that wzs the key to this chase: catching cells as they bumped the warm front.

Convection was bubbling on the warm front and we decided to track it on 80 east for a ways to see if it was in play. Since the sharply focused warm front was not lifting, these cells were almost immediately crossing into the cool air so we quickly saw they wouldn't be serious chase targets. In the open warm sector well to our south, however, a cell went up near Bloomington. We decided to head it off as it tracked northeast toward the warm front, intercepting probably somwhere along I-55 south of Morris. We continued down 80 and then drove south through downtown Ottawa on 23 before stair stepping east and south down to a spot northwest of Pontiac.

We got in front the cell, which was in the process of splitting to our southwest. We had a good view of the left split base, but we were looking into the forward flank rain of the more interesting right split. The cell picked up a severe thunderstorm warning which cited a motion of northeast at 40 mph. Not wanting to jump the gun with a fast motion like that, and because the warm front still seemed to be the critical intercept point, I decided we should hold here and let the cell pass by us The nearest surface observation to our north was north of the warm front, and the nearest to the south was solidly in the warm sector. The warm front was somplace nearby. We started to get into the forward flank rain and moved east to get out of the way of the core when several reports of a rapidly rotating wall cloud came in. I decided we better get in there and we boogied south to get eyes on the base. Brindley pointed out the hail core on radar, but I wasn't super concerned by it, not knowing that softballs were starting to form. We clipped the east edge of the core getting a few stones probably less than an inch in diameter.

A backlit wall cloud with lots of motion came into view. We stopped a few miles to the northeast expecting it to track to us. Small hail pinged off the van as we sat on the edge of the forward flank precipitation core, which I expected to be moving off of us momentarily. Meanwhile, the hail was growing to monstrous sizes to the west.

The storm spun up a brief, non-condensed tornado just as my phone buzzed with a tornado warning. The zoomed-in camcorder picked up the ground circulation, and Brindley pointed out the dust below the wall cloud as it was dissipating. I missed seeing it entirely while texting my niece who lives nearby that she was in the clear. What looked like little more than a gustnado from our vantage, we likely wouldn't have been able to confirm it anyway, so I'm not even going to count it.

The precipitation only increased at our position and I realized the storm was turning hard right, slowing down, and the forward flank expanding in size. We could have gotten on the base much sooner and gotten much closer. We had to drive a few miles south to get out of the rain, and then we were still in the path of the wall cloud due to the right turning motion. We had good visibility, roads, and the wall cloud was retreating so we let it approach.

The base started moving overhead revealing a large clear slot and occluded updraft.

This was my favorite moment from Tuesday’s chase. It looked like two occluded circulations up in the storm’s base. The cyclonic on the left, maybe remnants of the brief spin-up bird fart tornado near Pontiac. The tilted updraft tower with billowing convection above it shining white in the clear air. The patch of sky blue and fluffy white is juxtaposed next to this stormy teal colored eye in the dark slate cloud base, what I’m guessing was an anticyclonic bookend swirl from the rear flank downdraft. I love when you can stand outside and just watch the clouds move overhead and all around while feeling the wind. I’m taking in the whole scene, but Brindley is pointing out the tiniest little detail. The smallest snake of a funnel is poking out from behind the base. It looks like just a hair in this ultrawide shot. You can play Where’s Waldo and try to spot it if you like. I lost, and Brindley had to show it to me on her camera’s LCD.

We stair stepped east and north, throngs of chasers now moving about on the grid with multiple cars at every intersection. The updraft base on the storm started to retreat, the hook disappeared from the radar, and the tornado warning was dropped. We hit the "conga line", long lines of chaser traffic, but the Illinois road grid enabled us to keep moving without issue. The storm started to kick up a big shelf cloud and it looked like it was gusting out. We expected an HP transition, and were now questioning if we wanted to follow this thing all the way into Indiana. It would be a big gamble leaving it. The storm could reorganize as the environment remained favorable to the east. But I guessed it would continue on as an HP hailer even if it went tornado warned again. The increasing level of traffic would make it difficult to get in front of the storm again, one of the few locations with visibility. We decided to leave the storm and go after new development on the cold front near Peoria, which was still little more than bubbling showers at this point and with only an hour and a half of light or so remaining in the day.

We drove back west following the grid until picking up larger highways. Our original cell did indeed regain its tornado warning, followed by a string of tornado reports near the IL/IN border. Huge, softball sized hail was also being reported on the storm, so we were both disappointed we had left, but relieved weren't caught in the core. Meanwhile the cold front storms went up, but then relatively quickly congealed. We didn't get on the line until dusk, took one peek at the mediocre gust front, and then turned around. We blasted ahead of the line and then called it a day, stopping in Ottawa for the night as we didn't want drive home in the dark and through a bunch of weather.