Forecast Discussion – March 30, 2023 – Bimodal Severe Weather Outbreak Expected Tomorrow

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For educational purposes only. If you live in the affected areas, please stay tuned to your local National Weather Service office for the most accurate and up-to-date information.

March 30, 2023: A bimodal outbreak of significant severe weather is expected tomorrow (Friday, March 31) from the Midwest to the Mid-South. The SPC has outlined two Moderate risk (level 4 of 5) areas, one across southeast Iowa into western Illinois and one farther south along the Mississippi River delta in northeast Arkansas, western Tennessee, and the Missouri bootheel. A strong closed upper low will migrate into the region, coupled with a deepening surface low. A broad warm sector will be in place from Iowa south to the Gulf Coast states. Semi-discrete supercells will initiate ahead of the surface low/cold front across central Iowa by early afternoon Friday with mostly a large hail threat. The (strong) tornado threat will increase farther east amid very favorable thermodynamics and strong low-level shear/vorticity along any surface boundaries. However, the amount of time that storms will remain semi-discrete may be somewhat short, limiting the strong/long-track tornado threat due to a quick transition to a more linear mode. Farther south, both the cold front and a prefrontal trough should initiate semi-discrete supercells in and around Arkansas. Intense wind profiles will be in place; if robust instability can be realized, strong/long-track tornadoes are possible.

My video on cold-core tornado environments: https://www.youtube.com/watch?v=W00SxO2UcYo

Contents
0:00 Introduction
2:07 Current observations
7:24 Model analysis (NAM, CAMs)
39:28 Analog – March 28, 2020
44:22 Analog – April 9, 2015
47:09 Summary

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45 thoughts on “Forecast Discussion – March 30, 2023 – Bimodal Severe Weather Outbreak Expected Tomorrow”

  1. Thanks for this. I’m in the St Louis area and, while it looks like we might not be in the super high-risk area, I’ll definitely be keeping an eye on things. Safe chasing if you go!

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  3. Ok now that I am well rested from the overnight shift now I got a better look at this. Hehe yup your right more daytime threat for prime stuff. Lets say 14 hour shift then loooking at model not a smart call when tired. 😉

    Anyway this is gonna be so nutty… As mentioned before it's been so long since I can remember seeing 2 moderate rest areas and it's really crazy that these areas have the potency as high as they do. Like we are already trending to be in a very very active tornado season and in general just severe season overall as we're transitioning into the El nino. As one pointed out out these transition seasons can be very very wild at times if they happen to hit at the right time of year like this is it seems.

    I mean the stuff that's up in Iowa is just gonna be bonkers as far as how high the ceiling is before everything among the entire line lines out into potentially the big D word. Hodographs are nuts. I just really really really hope that if chasers aren't able to get any of the tornadoes that would form in the window that these storms will be discreet before they completely line out into a ridiculously big duration online that I just really really really hope that if chasers aren't able to get any of the tornadoes that would form in the window that these storms will be discreet before they completely line out into a ridiculously big derecho line that we see some nice shelf cloud pics. Like I really like my soft cloud videos and shelf cloud photos as mentioned because we usually just get that majority that time during severe storms appear in Albany so I'm used to seeing them and just enjoy filming them compared to most to actively live in the plains or Southeast or in general just chase so much more stuff.

    Trey not sure which of the 2 MDTs you'll do but…Northern mode I like Williamsburg, IA right on I-80….Southern mode I would favor Carlise, AR. Hehe though in all honesty someone will get something this entire event….I mean it is wild that you basically are getting chasers across the U.S….even some Northeast people flying into IA to meet up with people to chase this event….I will wait till Jine as usual with my friends. 😉

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  6. I think the HRR has been terrible at the convective out, I think it tends to show more supercells than there actually will be and should be taken with a pinch of salt 90% of the time

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  7. As someone learning this stuff and who likes pattern recognition, Do you even look at the, "Potential Hazard Type" designation when looking at Hodographs?

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  8. Are you going to be chasing the southern mode or northern mode. It would be really helpful to spot the ones in the south due to the higher moisture content while the northern one usually is more photogenic and the people up their will see it but its up to you on where you want to go

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  11. The best bet will be which moderate risk area is less likely to fail mode… Not suggesting either would be a bust, but perhaps not pan out to expectations as you pointed out the potentially problematic issues in both areas. This is a tough bet for any chasers driving a considerable distance to not pick the "wrong" moderate-risk area. Dang lol.

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  13. ty bro for your videos, you always put a ton of effort in discussing these outbreaks and i really appreciate it! my hometown in the quad cities is one of the places in the moderate risk zone (i dont live there anymore) and im in the enhanced risk zone, so im a bit worried, but staying informed is super important and helps me feel a bit more prepared and safe! once again tysm for these 🙂

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  16. Truly the best severe wx setup and post-event analysis work available. Tremendous. Likely beyond the scope of the comments section, but very interested in why 'convective allowing' models (HRRR etc.) are named as such, and why you tend to discount their solutions somewhat vs the, I guess you'd say, 'non-convection allowing' or standard models i.e. standard NAM. Absolutely understand if too involved to get into here, and can easily enough find out from my own research, but always interested in your explanations of such things. I've been fascinated by weather since I happened to take a freshman met 101 class as a science category fulfillment lib arts degree course and loved it (which was just a FEW years ago lol…) You're gifted indeed at imparting complex specialized information and it's meaning in ways the layperson can easily understand, and learn ever more about the incredible atmosphere we live in and under. Thanks for the time and effort so clearly put into the work you share.

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  21. Please do not ignore southern Missouri . The only reason weatherman talk about jonesboro is cause it's a larger city. Largest till u go up to st Louis and over to memphis. Just as many people live in this rural area. We need the info. No weather help from larger city stations. No warnings reach the more rural areas .

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  25. 19:16 let me see if I understand. So because of the wind shear, it causes tubes of air at the surface. Because of (thermodynamics? Instability ) the t-storms can ingest those much easier, and when they do that leads to mesocyclones/ tornado genesis?

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  27. Another superb breakdown Tre! I'm learning a ton as I follow along with your graphics & explanation. Kudos!👍👍 Wishing you & your chase buddies safe travels, and a successful chase tomorrow! 🙏

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  28. I live in iowa where the moderate chance is located. Got my wine for tonight Xanax for tomorrow and hopefully my soul sticks around. I'm probably one of the most scared ppl of tornadoes that any of my family knows of. Got my weather stations phon number programed in my phone. Plotted my basement safe spot in my head. Tomorrow possibly packing valuable items to take to basement save my kids then my cats then I should be ready.

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  31. As per usual, fantastic breakdown Trey, really digging in yet again, and I can't get enough of learning more about all these little bits of nuance. Thank you, and as always here's a wall of text with my notes/thoughts on the event!

    Well the event has been getting hyped for a while, and it has all the potential to deliver on the hype for sure. There's some questions in each of the two main regions, but if those questions resolve we have some fairly obscene parameter spaces. Areas of 250+ 3CAPE up north, areas of 500+ SRH down south, both of which are incredibly potent for different reasons.

    Up north especially looks like a "snap your picture, get your 30s video, then get the hell out of dodge" kinda day. With the incredible speed of those storms, it'd be very easy to get caught if you're not careful. Hopefully no more unfortunate storm chaser mistake stories come out of that one. The 3CAPE across the board is very frightening, even up into Southeastern Wisconsin where there's still some favorable winds, just a bit more early-day showers to potentially keep things at bay. But I think the moderate risk needs to go a bit further into WI. Also the northern extent is not particularly streamwise with its vorticity because the winds jet off to the right on the hodograph very quickly. I doubt it will matter that much with the insane low-level instability that ANY vorticity is getting stretched into the vertical easily, but it might be a factor in limiting the ease of rotation in the updrafts.

    Down south the main thing I'm looking at is the weak capping potentially filling up that instability in the morning and early midday hours a bit more than the models are showing right now. There's some semblance of an EML, albeit a very shallow one, that might work to pressure cook the area just a little bit. The pre-frontal trough is very concerning, as you and the SPC both mention, and I'm even seeing a small kink in the flow in Northeastern Arkansas at 500mb on the NAM, along with ample diffluence aloft over Southern Missouri. I honestly would not be surprised if the combination of weak forcing and low instability makes the event MORE potent in the southern section simply because there won't be as many explosive updrafts that run into the frankly obscene and horrifying wind profiles. There are some sections potentially seeing over 600 m2/s2 of effective SRH and very streamwise vorticity. Whatever updrafts form are going to be spinning like a top from the moment they appear. The low instability may stop them from exploding fast enough before a more linear mode takes over, but I am extremely concerned about how much spin is going to be in the low levels.

    I also think East Texas and Northern Louisiana need to keep a close watch on things even though they're currently a bit outside the enhanced zone. There's some concerning patterns showing up at a synoptic scale that if the CAMs happen to be right and storms fire that far below the trough, they might end up seeing some potentially severe weather as well. I'm seeing all the right parameters for tornadic supercells if the cap does, in fact, manage to break that far south.

    All-in-all, another one of those events that's an obvious "not a slam dunk" and can easily be a huge bust on both fronts as the north is potentially going to be contaminated by early day rain and potentially not see enough of a wind profile to spin things, and the south may end up not seeing enough instability to erupt the updrafts to the degree needed for severe tornadoes. But just as I said last weak, with the parameter space in place, there's some frightening potential here. To see the type of thermodynamic profiles we're seeing that far north feels very abnormal to me this early in the season, as well. Very wide reaching moisture returns and low-level instability in spades. Either way, I hope anyone that lives within 100 miles of the Mississippi river is keeping an eye on the weather tomorrow!

    As always, thanks again, and stay safe out there! Gonna be a very fast day!

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  32. Me and Mother Nature are gonna play catch Friday afternoon. I live in NE IA, and need to go to a family reunion in North Central IA, so if i time the commute just right, i might get to wave at a tornado as it speeds by…. 😂 I may have to detour a bit south, we'll see🤔.

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  43. I think the worst part is now all the 10% chance is considered hatched, it's also grown a lot, very concerningly large area of the midwest is now under a 10% chance of EF2 or higher (hope and pray that we can get through this unsctathed, because all we can do is pray)

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