2024-05-06 EVENT: TX/OK/KS/NE

[Dan Robinson]

Medium-range models have shown consistency and agreement on a negatively-tilted shortwave trough ejecting over the central and southern Great Plains on Monday May 6. This is shown occurring over a large warm sector with ample moisture ahead of a dryline with a breakable cap from north Texas through Nebraska.

At this early stage in the forecast cycle, models have been wavering on the timing of the wave's ejection over the Plains. This is ranging from an ideally-timed major tornado outbreak scenario to an early ejection with storms firing at mid-day. Today's runs have trended toward the latter.

From a chase trip planning standpoint, models have been trending toward this being a single-day Plains event, with subsequent events potentially being far to the east and south in the Midwest or Arklatex. Still, strong flow and deep moisture are regionally coexisting on those days and subsequent Plains overlaps of the two may come to fruition.

 

[Patrick K]

12Z global models seem to be slowing the progression a bit relative to last night. There seems to be a lot to like about this setup in addition to just the appeal of an aptly-timed central plains negative-tilt upper trough in early May. The 12Z GFS likes a modest EML eroding by mid-to-late afternoon, with a sharp dryline extending south from a surface low. Storm motion is expected to be roughly orthogonal to the dryline and 0-2km wind profiles will provide support for what seems likely to be a line of discrete/semi-discrete supercells popping off the dryline. I think this will be in range of some of the CAMs soon which I expect to support the idea of several hours of discrete mode.

For me, items of concern are the slightly just in time dew points and predicted cloud cover. As usual, it bears watching the evolution of Sunday's convection.

If I were chasing, I'd target the dryline bulge in central Kansas. There's a lot of reasons to be bullish about this event, but maybe I'll avoid the jinx by expecting the ingredients to fall apart by Sunday.

 

[Derek Weston]

Wonder about mode on this one. Seeing rather unidirectional hodos but for some good turning below 850.

 

[JamesCaruso]

Wonder about mode on this one. Seeing rather unidirectional hodos but for some good turning below 850.

I agree with this. Definitely a chase day, but mid-level shear sucks. HP storm mode likely.

I'm biased because I can't chase anyway. Too many work commitments, especially ahead of my chase trip that begins 5/13. Wish I was the type to say screw it and head out for this. But I'm not, so I look for failure modes

 

[Dan Robinson]

As shown now, the southern Nebraska/northern Kansas zone on the northern half of the arc back into the low looks prime as long as the 60F dewpoint line can make it up there. The NAM's low-level hodographs look pretty solid most anywhere north of I-70 despite the linear look suggested by some models' simulated reflectivity. This is looking like another "trip to Salina the day before", expecting to either go north or a little west in the morning.

The meridional flow/linear mode issue is a concern now, as is the potential for early-day cloud cover. That's something that is almost always there to some degree with a big wave. But a system like this coming into the Plains in May with moisture mostly in place? "If it's May, you chase" applies with even a tenth of what's shown (especially in a year like 2024 that seems to want to produce). Meteorologically speaking, I can't see a reason to ever turn my back on a setup like this if I have the ability to be there.

 

[Jeff House]

This is a somewhat mesoscale post 60 hours out; so, take it for what it is. It needs to hold until it's at or inside 36 hours.

12Z Saturday NWP for Monday shows a secondary jet max in the southern stream, punching into OK/KS, south of the teardrop mess north of KCMO. LLJ responds from OK into southern Kansas. Related, another subtle east-west boundary is forecast to lift from OK into KS and perhaps intersect the KS DL bulge. This secondary TP would be well south of the possibly occluded mess north of KCMO.

The downside is the farther south, the closer to mega chaser convergence. Situational awareness will be critical.

 

[gdlewen]

This is a somewhat mesoscale post 60 hours out; so, take it for what it is. It needs to hold until it's at or inside 36 hours.

12Z Saturday NWP for Monday shows a secondary jet max in the southern stream, punching into OK/KS, south of the teardrop mess north of KCMO. LLJ responds from OK into southern Kansas. Related, another subtle east-west boundary is forecast to lift from OK into KS and perhaps intersect the KS DL bulge. This secondary TP would be well south of the possibly occluded mess north of KCMO.

The downside is the farther south, the closer to mega chaser convergence. Situational awareness will be critical.

Sorry--can't find station KCMO--where is that? (Thanks!)

 

[Mike Smith]

Sorry--can't find station KCMO--where is that? (Thanks!)

It is how natives describe Kansas City, MO. There are three primary wx stations in the KC area:

• KMCI = Kansas City International Airport, north of downtown KC
• KMKC = Downtown KC Airport
• KIXD = Olathe, New Century Airport, southwest part of the Metro

There are several other ASOS but those are the primary.

 

[Mike Smith]

Here are my initial thoughts regarding Monday.

If I were a lead forecaster at SPC, I'd be going moderate (15%, hatched) in the area in the sketch. I'd go enhanced (10%, hatched) north from the red outline into southeast Nebraska, include KC to MLC to ACT.

In theory, when SPC went from 3-levels (SLGHT, MODERATE, HIGH) to 5 (MARGINAL, SLIGHT, ENHANCED, MODERATE, HIGH),nothing was supposed to change w/r/t Moderate and High. In reality, SPC treats moderate like "high" in the old days.

While it doesn't matter much to me whether they go HIGH* or not, it wouldn't surprise me to see a high issued in the 11:30a or 3pm Monday outlooks.

If I chase Monday (and I may), I'll probably stay in Kansas because of the better road network and I think it could be prime for tornadoes.

Addition at 5:45p Saturday: I've been playing with the SPC climo for the past hour and, at surface, 500 and 250mb, Monday looks a lot like May 8, 2003. If it were a perfect analog, my red area should be moved about 70 mi to the NNE. Still think my outlook is pretty good but the climo is something to keep in mind and reinforcing my decision to chase in Kansas.

And, 5-8-03 was a HIGH risk day.

 

[Todd Lemery]

Interesting setup. While some CAMS show over 4000 MLCAPE in mid Oklahoma, the forcing isn’t as strong there and there’s a chance nothing goes up there at all. I think the CAPE numbers are inflated a bit, but at least a couple of storms will pop. Going farther North there’s a very real possibility that a lot of the storms in Kansas will line out before getting the chance to fully organize. That would seem to make the case for a happy medium and going to Southern Kansas. The only troubling issue I see with that is the amount of trees East of Wichita. It’s not as bad as it is East of I-35 in Oklahoma. It is a concern though. The wind profiles are good throughout the region , but a bit better in Kansas than in Oklahoma where the lapse rates look a smidge better. I’m thinking of getting some help from GOES in the morning hours and letting the best daytime heating make the call for me.

 

[Amelia Urquhart]

I might be subconsciously biased since I have a final ending at 3:30 and won't be able to make the Kansas mode, but I lean more toward the Oklahoma mode. NWP suggests that shear vector orientations will be much more favorable for discrete convection further south and less favorable north of Dodge City. Forcing is admittedly weaker, but I think the height falls from the trough ejection will still be enough to get it done. I'm currently planning to chase southwest or west central Oklahoma, and I'll take a risk of a blue sky bust in exchange for a better chance of discrete convection if storms do manage to fire.

 

[William Monfredo]

I haven't posted in years, but I've been watching regularly . Chiming in, not hard to believe that isolated cells or tail-end storm in south-central, KS or northern OK produces photogenic / damaging tornadoes, despite more linear convection further north.

 

[Dan Robinson]

That's quite the shift in the surface/dryline pattern from 36 hours ago. The model signal for storms south of the OK/KS border at 00z in the better CAPE is pretty strong now, and that's a scary environment. Scary not only tornado-wise but chase-terrain-and-roads-wise east of 35. I'm not sure I buy Kansas completely lining out, though. There's not much difference in that environment between a squall line and closely-spaced tornadic supercells going nuts. That being said, I may shift my overnight spot from Salina to Emporia to hedge a little south. I'm nervous doing that, though, with fast NE-moving storms. Hedging more north toward I-70 keeps the border action in play if needed, but rules out making anything in Oklahoma. The OK storms' more easterly motion would be great if it were just 100 miles farther west. Will be watching and hoping for a slower and farther west trend for that reason.

 

[JamesCaruso]

Both Euro and NAM have the dryline close to the OK border with the TX PH. GFS, not surprisingly, is more progressive so I would probably discount that. Should be plenty of “room” to chase west of I-35. The scary scenario is the typical craziness in that region with chaser hordes, congregating around a likely fewer number of discrete storms, combined with rush hour traffic around OKC, and fast-moving storms. At least it’s not a weekend, so maybe fewer chasers and local yahoos, but rush hour traffic will be a factor the closer you get to OKC. I typically don’t let chaser convergence affect my chase targets, but this time I’m not so sure. But I won’t be out there anyway, so I don’t have to make that decision. Be extra careful everyone!

 

[Mark Gressman Jr]

NAM3K has a discrete cell going up near Altus. There's agreement in guidance with jet placement in the SW corner of Ok around the 00z timeframe. A possible secondary low in the NW corner looks to occlude and produce some focused convergence, while a shortwave comes through to help with CI. CAPE should be plentiful, although helicity doesn't take off till near dark with the help of the low level jet. There's been a fair amount of change in guidance on the placement of parameters in just the last 24 hours, but like Amelia, I Iike the southern play for better storm motions, even if it means blue skies. I'd like to think that area around Altus will shape up nicely in the next 24 hours.