2024-05-24 EVENT: IA/IL/WI

[Dan Ross]

Becoming increasingly interested in Friday afternoon's setup in eastern IA/northern IL. Should have some decent southwesterly 500mb flow associated with a negative tilt trough. Per usual for the region, an ongoing line of storms will be moving through in the morning hours, which can make or break the afternoon potential... HRRR has some consistency showing an outflow boundary stalling out somewhere near the Quad Cities. 00Z NAM on the other hand has morning convection plunging south into MO. My plan is to position just north of the boundary as things (hopefully) destabilize in west to east fashion in time for afternoon convection to thrive. Afternoon soundings in northern IL show nice hodograph curvature and 0-1km SRH 200+. There's impressive veering with height with such nicely backed winds along/north of the boundary, which should allow for slower storm motions too.

My forecasting attempts are probably overly reliant on the HRRR (especially when it's trending so good ), and I think this is my first Target Area thread. Interested to hear what others think and what I'm leaving out.

 

[Jamie H]

Feels like a difficult forecast for novices like me!

Not all models show strong flow aloft, some have better backing of winds, and only the HRRR shows storms behind the ongoing convection. I would probably target northeastern IL, but without much confidence.

 

[Blake Naftel]

Mildly caffeinated overview: Friday [today] afternoon is certainly one remain fluid with and know the boundaries in many regards, both convectively and geographically speaking.

The big SVR bow/MCS with embedded lead circulation/s that’s presently barnstorming east towards the Quad Cities at 8/8:30a EDT, 7/7:30a CDT will likely lay a boundary down “somewhere” in north-central Illinois over towards metro Chicago later, as alluded to in multiple flavors of CAMs, some more aggressive, others like the NAM 3k far less. Ample moisture already evident via obs. in S/Central Illinois that the MCS is working into.

With early/mid-afternoon mid/upper-level assistance and inbound secondary low that will likely develop and gravitate eastward towards western Lake Michigan [Kenosha, WI region] by 5p CDT’ish, there’s most certainly a risk for a strong tornado or two with any discrete supercell that can establish itself ahead of any advancing bowing storms along the initial cold front baring that scenario materializes in nature. Not seeing this as a localized tornado outbreak day, more of a dominant embedded tornado/severe wind type of storm mode/morphology -- yet one of those events that could easily pack a punch.

Downsides, lots of post morning MCS cloud cover and overall likelihood for a murk-style storm observing. Also, any storms that can/do form will encroach on the western suburban and metropolitan Chicago zones, which for chasing/observing is never one I favor or now jump at even if in close proximity to home. Traffic typically bungles all efforts and awareness of the local road networks are vital.

From all the early morning data consumed with coffee: perhaps a Belvidere > Marengo > Rochelle / US-20 east of Rockford southward and east of I-88/I-39 focus zone to start early [2/3p CDT].. merely due to likely boundary placement and assorted parameter alignments, more rural terrain [away from Rockford and west of CHI]. Southeast Wisconsin ahead of the secondary area of low pressure also has ‘that look’ of an embedded tornado/severe wind event day. Even concerned for a substantial severe wind threat all the way into the Southwest Lower Michigan/Eastern Lake Michigan shoreline region if PM storms in N. IL can get cranking. Shall see what transpires, or atmospherically fools, anyone out and about today.

 

[Dan Robinson]

Well, I missed Eldorado to chase this, so I need to not mess it up if I can. The good sign is that there is not a huge MCS plowing through eastern MO this morning. Instead, it's clear and sunny in most of the area. There are two boundaries in play today, an NNE/SSW one in central MO from the northern complex and another moving north from an MCS in the Missouri bootheel. Both boundaries are still on the move, which usually is not a good sign at 9am - normally you'd want those already stalled out. If they're moving, they're still fresh and cold and are going to take more to warm up. Although the southern boundary is already out in the sun, which is good - new storms are trying to go up on its leading edge. The southern MCS will also stunt the low-level flow for both target areas. It looks like by 00z we'll have 30kts+ flow above these boundaries. So if storms can hold off until at least 4pm, I think the chance for a supercell or two interacting with one or both of these boundaries is decent. I would favor the intersection of those two boundaries, which looks like it might end up southwest of St. Louis on the I-44 corridor.

 

[Dan Ross]

Thank you for highlighting the many uncertainties for today to counter my wishful thinking forecast! Indeed greater potential for messy/linear modes overall. My target will be the boundary across northern IL, as I live the Rockford area and wasn't planning on a big chase today anyway. Hopefully it settles out soon and we get a little clearing

 

[Blake Naftel]

With the morning caffeine now subdued and post MCS passage which, rather impressively, is still maintaining an eastward SVR threat now around Gary, Indiana... Surface obs. in the initial zone outlined earlier are really worked over in N. IL. and I don't see any earlier suggested "event" now happening. Unless more substantial convection goes along the initial CF into NW/N. IL or within the S. WI warm frontal murk zone, I would be surprised if a supercell or two now even materializes. Seems the NAM 3K may have been spot on with today's trends. Boundaries south towards N of STL and the cluster bombs of water vapor seem to be "the scene" so to speak for now.

 

[Andy Wehrle]

Multiple HRRR runs insist southern WI will destabilize in time for an evening round of severe convection, even as more garden variety storms are rolling through at 1400 local time, keeping it overcast.

 

[Diana Nevins]

I just hope any severe storms hold off until after 10 PM, and I am flying into O'Hare this evening to spend the weekend with my father!

 

[Blake Naftel]

Well, I'm surprised, but a new SVR storm has indeed formed in "recovered" surface environment in 76/62 T/Td air in easterlies.. moving towards the original focus zone outlined this morning. Could definitely have some ice bonkers as it progresses NE, of which, that storm could be "the event" as it were. Watching from a far and monitoring now n' then.

 

[John Farley]

A couple decent-looking storms on radar in the wedge of juicy, unstable air southwest of STL Pretty unidirectional shear there, though. Better directional shear appears to be southeast of I-44, likely on the cool side of an outflow boundary from the bootheel MCS Dan mentioned. Makes me wonder if storms will survive if they move into the better directional shear, but perhaps the larger dynamics of the storm system can keep them going. Chase terrain between I-44 and I-55 is terrible though. Anyone coming from the north, be on alert for flooding north and northeast of STL, as heavy storms have been tracking over the same areas repeatedly and still are.

 

[Dan Ross]

Well I wound up in northwest IL getting some close CG strikes and some pea sized hail. Looked like storms struggled to be surface-based and stayed quite disorganized. Had some filtered sunshine throughout the afternoon in northern IL but it was too little too late .

 

[Andy Wehrle]

Well I wound up in northwest IL getting some close CG strikes and some pea sized hail. Looked like storms struggled to be surface-based and stayed quite disorganized. Had some filtered sunshine throughout the afternoon in northern IL but it was too little too late .

I think we're currently getting about our fourth round of thunderstorms of the day here in the Madison area. Quite vigorous, too despite the limited recovery window behind the first two or so. I think today could have been rather significant in this area with better recovery behind the initial AM line and without any additional convection firing until about 22-23Z.