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April 12th/13th and 15-16th Severe Weather Thread


andyhb

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As I look at tonight's NAM I'm beginning to wonder if May/June like capping may be an issue in OK and KS for Saturday at least per precip maps and simulated reflectivity. It's strange to be having a large amount of CAPE and wondering if anything will fire in mid April. Warm front looks active along I-80 corridor in the Midwest.

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As I look at tonight's NAM I'm beginning to wonder if May/June like capping may be an issue in OK and KS for Saturday at least per precip maps and simulated reflectivity. It's strange to be having a large amount of CAPE and wondering if anything will fire in mid April. Warm front looks active along I-80 corridor in the Midwest.

12z run showed the same thing. With that said, the wind profiles look extremely impressive on the 00z NAM over a large area on Saturday and the 700 mb temps do not look overly inhibiting across much of the threatened area, with the higher mid level temperatures being confined generally south of DFW. H5 temps look good too, -10 degrees or less across the entire warm sector throughout the day.

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yeah the 00z NAM, 0-1 km EHI is nuts Saturday evening/night. It goes nuts down the entire line after midnight even. CIN does increase down into OK as the night wears on. The wind profiles are pretty wild as well.

NAM_221_2012041200_F75_EHI_1000_M.png

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The only way capping becomes an issue IMHO is if the trough ejects significantly slower than what is currently progged, as Cheeznado alluded to earlier. That's probably the most likely thing that can go wrong with this setup. Although the NAM appears to have a late intiation, I wouldn't take that too literally because at least from eyeballing the synoptics and looking at the forecast soundings, the synoptic-scale forcing should be more than enough assuming the timing is close to correct. Aside from the precip output, the NAM is pretty much a textbook Plains outbreak.

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Blows up a discrete storm in southwest OK between 0-3z.

Good catch.

Either way, the period between 18z Saturday into the early morning hours of Sunday looks pretty incredible on the NAM, considering the strength of the LLJ, it clearly looks like the NAM is underdoing the LL helicity values on Saturday, the 0-3 km EHI before the map JoMo posted is already ridiculous across a large area. Any OFBs that linger in the warm sector from possible convection on Friday will locally skyrocket LL shear as well.

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The only way capping becomes an issue IMHO is if the trough ejects significantly slower than what is currently progged, as Cheeznado alluded to earlier. That's probably the most likely thing that can go wrong with this setup. Although the NAM appears to have a late intiation, I wouldn't take that too literally because at least from eyeballing the synoptics and looking at the forecast soundings, the synoptic-scale forcing should be more than enough assuming the timing is close to correct. Aside from the precip output, the NAM is pretty much a textbook Plains outbreak.

yeah just looking at hodographs..they are impressive over a large area and only get more crazy by 3z.

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Good catch.

SW OK really gets raked if you buy this run's precip output literally (which I certainly don't). Evening activity in a monstrously-sheared boundary layer both Friday and Saturday.

I'm a tad concerned about the rather significant flattening of the H5 trough compared to last run, in that if that trend somehow continues unabated for the next 48 hours, it really could start to scale back the potential for Saturday. Provided it's just part of the ebb and flow of solutions, though, it still looks incredibly ominous -- as CUmet already said.

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130-150 knot 300 mb jet over New Mexico Saturday evening on NAM is frightening to contemplate when one thinks of potential with this system.

Instability look plentiful well into the overnight hours, and with continuing favorable shear vectors, could get really bad after dark as the LLJ strengthens rapidly.

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As I look at tonight's NAM I'm beginning to wonder if May/June like capping may be an issue in OK and KS for Saturday at least per precip maps and simulated reflectivity. It's strange to be having a large amount of CAPE and wondering if anything will fire in mid April. Warm front looks active along I-80 corridor in the Midwest.

I agree, I always have thought that the Saturday SPC outlook should go at least to DMX maybe as far north as Waterloo IA, If the Nam verifies (although this is not in its wheelhouse yet,) look at the EHI Values north of DMX, it will be interesting to see what the SPC does tonight.

wrfUS_3km_EHI_72.gif

I was about to give up on severe in MN but now I'm not so sure with the 12/0z run of the Nam, but again its towards the end of its run, let see what the GFS and Euro show when they come in.

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To those going out on Saturday, I would like to caution you to be careful and even though you may want to get close to the storms, please remember we're going to likely see an ungodly amount of "chasers" out there and traffic issues are likely. I'm hoping several storms will allow for a more even spread of chasers, but it's going to be hell on earth, both in terms of the tornadoes and the overall chaser convergence.

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To those going out on Saturday, I would like to caution you to be careful and even though you may want to get close to the storms, please remember we're going to likely see an ungodly amount of "chasers" out there and traffic issues are likely. I'm hoping several storms will allow for a more even spread of chasers, but it's going to be hell on earth, both in terms of the tornadoes and the overall chaser convergence.

This.

Thankfully with a big area it should help spread people out somewhat. Just hope I'm on the best storm!!

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Yeah Saturday sure looks like a widespread threat, which should keep chase convergence down a bit compared to some notable past events. The 00z NAM makes a strong case for eastern Nebraska Saturday to me. Although you can make an argument that KS and OK look just as good. Unfortunately for me I'll be stuck at work on Sat until at least 2, so I'm pretty much screwed unless we can get a setup on Sunday.

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ICT at 00z Saturday evening, barely any CINH, low LCL heights and plenty of shear/instability, and the warm front looks big up in NE/IA, especially with that EHI map MinnMeso just posted:

Might like to see a little more CINH in fact... Best U/L support seems to be two-pronged... very good early Sat. morning, then weakening slightly through the early afternoon before strengthening again late afternoon. I'd be concerned things go up a bit ahead of that second wave, and also that CAPE underperforms due to lack of sun.

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After evaluating tonight's model data, along with the DLF (David Lazy Factor) and the CCM (Chaser Convergence Model), I've elected to play in Western Oklahoma tomorrow. The 21Z SREF actually favors that pretty well tomorrow evening. I believe that Kansas will have the higher potential for tornadoes based on overall confidence in convective initiation, but I usually end up doing well playing the southern end of a system. Less chasers, less ruckus, and a better chance of enjoying my evening verses being stuck in traffic. It also puts me in a better position for Friday.

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Might like to see a little more CINH in fact... Best U/L support seems to be two-pronged... very good early Sat. morning, then weakening slightly through the early afternoon before strengthening again late afternoon. I'd be concerned things go up a bit ahead of that second wave, and also that CAPE underperforms due to lack of sun.

GFS/NAM shows pockets of stronger capping throughout the warm sector until at least 18z Saturday afternoon.

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