2025-04-02 EVENT: OK/TX/LA/MO/IL/IN/OH/KY/MS/AL/TN/MI

[Jesse Risley]

On the heels of Sunday's system after a brief return to quasi-zonal flow a very potent trough just coming ashore as I write this takes aim on the central and southern CONUS on Wednesday. Powerful southwesterly flow aloft begins in earnest on Tuesday as Gulf moisture once again begins to surge northward. By 12z/02 (WED) the 500 mb low looks to be situated over the Dakotas as the 100+kt H5 jet core of a negatively tilted trough noses over the mid-Missouri Valley. A very potent 75kt S-SW LLJ will overspread a large region from the eastern Red River Valley to the western Great Lakes as a sub-990 mb surface low moves from south of OAX to western Lake Michigan by 00z/03. The main surface forcing mechanism looks to be a pronounced SW-NE oriented cold front that is positioned from near DFW to Dubuque, IA by late morning WED as a warm front looks to lift northward into NE IA and SC WI. SBCAPE values AOA 1500 J/KG look plausible at this juncture across large parts of the open warm sector with values AOA 2000 J/KG possible largely south of the Ohio River valley. 0-6 km shear values up to 80 kt, favorable lapse rates, and ample speed and directional shear look to favor all modes of severe weather. However, the system is just now coming ashore and is just now coming into range of the shorter-term and late medium-range model suite. There are some signals for remnant convection TUE night into WED that could linger into WED morning or early afternoon especially north of lower Missouri River valley. The extent of any cloud cover, remnant convection, and residual OFBs will not be resolved this far out. This could impact convective parameters across northern portions of the risk area WED afternoon and WED evening especially for locations closer to the mid and upper-Mississippi River valley. Nonetheless, there are strong convective signals by late Wednesday from eastern MI to northeastern TX. Storm modes may be messier north of the Ohio River valley owed to more straight-line hodographs above the near surface layers whereas clockwise, curved hodographs are more pronounced across the southern portions of the risk area where slightly better instability parameters look poised to reside. There's still a lot to be worked out over the next 36-48 hrs but it looks to be a rather potent severe weather setup from the western Coastal Plains into the Great Lakes region WED and WED night,

 

[Matthew Crowther]

Probably sulling the trigger on the first chase of the season for us. Target seems to be NE Arkansas or SE Missouri- hopefully in the more open areas east of the Ozarks. Then the same general area for Thu-Sat. Maybe messy, but the cabin fever says go chase, especially since the following week looks quiet.

 

[Matthew Crowther]

My biggest worry is that storms may have trouble forming where the significant parameters are. The new 3KM and 15 NAM show just linear junk along the stalled front. The failure mode could be the lack of forcing under the building mid-upper ridge.

 

[Jesse Risley]

Further north, i.e., north of the Ohio River valley, the models seem to be depicting lesser instability owed to overnight convection and lingering cloud cover potentially modulating the thermodynamic environment across this region. That seemed evident on both the 12z/31 ECMWF and 18z/31 HRRR. They're also struggling with storm mode a little bit, although that's not really to be unexpected given some of the parameter space issues. Nonetheless, there will be plenty of shear and up north closer to the triple point and points east along the warm front might be an underappreciated high risk, high reward region to watch too. It could end up being that the only play across the far north in the open warm sector, outside of the potential warm front play, would be well further east towards the Wabash River valley later on Wednesday assuming instability can materialize across this region later in the day. There are also still some slight timing differences with the arrival of the cold front across western portions of the risk area too. On the other hand, residual boundaries left over by morning convection if the atmosphere recovers will also be something to watch.

 

[Dan Robinson]

The last few model runs have painted a bizarre picture of two target areas separated by 150 miles of precip and clouds, far enough apart that you will have to commit to one early. With no home area bias, I'd obviously go east of the mess of precip where there will be a better chance of pristine inflow, low-level shear and discrete storms (but in awful terrain). But that western zone in between the precip and the front has the look of one that ekes out some last-minute destabilization during the late afternoon and sends photogenic supercells/tornadoes right through my home area. Of course, going east guarantees that happens, staying here ensures it doesn't. Not much to do but wait and see how the mess evolves through the morning.

 

[Jesse Risley]

Everything that happens today and tonight impacts tomorrow. There is still quite a bit of variance amongst some of the models regarding timing of the surface features, the possible influence of a pre-frontal convergence axis, and the nature of shear profiles relative to the orientation of the surface forcing mechanism. It's still looking like the overnight and early AM convection may impact the thermodynamic environment of the northern sections of the greatest risk area so that there is mostly a threat of damaging winds and hail north of the Ohio River valley when a renewed line of initially semi-discrete storms erupts in the early afternoon east of the Mississippi River. If the atmosphere recovers and more generous instability parameters are met it would change the dynamic here although hodos still look to be more meridional than not. That seems to favor splitting cells and line segments. This looks somewhat similar to Sunday's setup. The greatest tor threat looks to lie across the lower Mississippi River Valley from AR perhaps into NC MS. That may extent eastward south of the Ohio River but that too depends on how storms initiate and what shear profiles actually look like tomorrow. I suspect remnant convective boundaries will also be in play across all areas that see some sort of convective activity tonight. I wouldn't consider upgrading any areas to higher probabilities until sometime tomorrow when all of this is more clearly delineated.

 

[Brian McKibben]

How are we feeling about the high risk today? Was it warranted?

I was thinking moderate for the initial and then wait until morning model runs and pull the trigger at 1630, but they came out of the gate with the high.

 

[Jesse Risley]

How are we feeling about the high risk today? Was it warranted?

I was thinking moderate for the initial and then wait until morning model runs and pull the trigger at 1630, but they came out of the gate with the high.

I was a bit surprised by the high risk especially for a potential tornado outbreak. I get that it is a highly sheared environment with strong kinematics but given the questions about instability placement and the propensity for messier storm modes I didn't expect an upgrade at 6z.

 

[Patrick K]

SPC seemingly doesn’t let questionable storm mode impact their decision for outlook upgrades very much. This system suffers from similar question marks to other underperforming “high” risk days - storm motion close to parallel to forcing, minimally or uncapped environment, cloud cover, previous convection, and in this case very narrow favorable parameter space.

It seems like SPC is quite confident in pre-frontal supercells, with discrete/semidiscrete mode due to more subtle forcing and in spite of lack of convective inhibition.

Some of the forecast soundings are pretty concerning. I found one near Little Rock at 00z with over 1100 SRH with surface east-southeasterlies beneath upper level west southwesterlies. If inflow could remain unimpeded, we could obviously see some strong tornadoes. But likely after dark. And only if storm mode cooperates long enough for updraft organization.

I would note that forecast soundings day of are considerably more concerning than days prior, where flow was more meridional and surface winds were struggling to back from the SE. that looked more like a boundary play. Today it looks more like storms will go nuts if they can mature in proper mode.

 

[Jason N]

if they get one long track EF4, I bet they'll look at it as it warranted their decision, lol, even if I too believe the MDT was enough for this set up.

 

[Jeff House]

High risk of a QLCS. I feel like we broiled up a high risk from the RRFS. Nothing else showed that kind of Southern Discomfort scattered spaced supercells. HRRR hints at some right in front of the line, but those tend to get gobbled up. I like the 45% hatched for wind (update).

I'm still an Under on 30% tornadoes. Then we have the 14-15Z HRRR showing discrete way out in Middle Tenn. Feel like that's the typical mid-morning HRRR hiccups. Low level wind shear is very strong there, but the mid-levels are warm. I don't see just-right warm for isolated powerful. I see turkey tower warm. I could be wrong!

Meanwhile it's a tall order to keep the ongoing line discrete. Could grow upscale through the afternoon. Now if the LLJ recovers particularly well I've seen lines break up again. That would be awful for the Mid-South public because that would be 30%. My conceptual model (not NWP) is more QLCS and maybe even a couple strong - which can happen within a line so 15%.

We'll see about the high risk. I don't see anything worth chasing today. Could change quickly if trends shift markedly.

 

[Randy Zipser]

The BBC just published an article online that this synoptic event over the U.S. today will be a "once-in-a-generation" rainfall event, especially for KY/MO/TN. For those of you chasers who are watching the situation closely today, do agree with that assessment?

US storm forecast to unleash flooding rain and life-threatening tornadoes

 

[Dan Robinson]

Models have not really been handling the evolution of today well. They have, so far, far overdone storm coverage in terms of the overnight line, but despite the lack of junkvection we're still solid overcast most everywhere. That is likely to impact our low-level CAPE. Also, storms are already a couple of hours behind schedule, at least here in the St. Louis area. That gives us some more moisture advection time. I'll be staying here and moving east with the line on I-64 or I-70, as I'm not convinced the High Risk will be worth the 4-7 hour drive. If our activity up here can stay discrete, the environment in the Wabash River area looks to be sufficiently volatile just before sunset. Despite that, this feels like a rain-wrapped QLCS (possibly sig) tornado day. My expectations for something spectacular are pretty low.

 

[Brian McKibben]

We have that elevated stuff in northern LA moving into southern AR. It has struggled to get rooted into the surface. Perhaps there is some low level capping issues. It will be interesting to watch as this continues toward the NE (memphis) area.

If we can get a nice firm updrate then perhaps we will see some discrete cells ahead of the line.

 

[Jesse Risley]

The BBC just published an article online that this synoptic event over the U.S. today will be a "once-in-a-generation" rainfall event, especially for KY/MO/TN. For those of you chasers who are watching the situation closely today, do agree with that assessment?

US storm forecast to unleash flooding rain and life-threatening tornadoes

NWS Paducah is saying "significant and may be historic" in its public statements; 10"-15" of rain is a lot for that region.