2012-04-01 FCST: OK/KS/TX/MO/IA

[Skip Talbot]

What a roller coaster ride this system has been to watch on the models, eh? We're finally getting some run to run consistency and the ECMWF and GFS are in general agreement on the placement, orientation, and intensity of a large trough moving into the plains on Sunday. The setup is a far cry from what the GFS was showing in earlier runs, however. At the surface we've got an extremely impressive pattern: 984 mb surface low, 65 degree dewpoints backing up to a sharp dryline with 15 knots of backed surface winds. Wow, what more could you ask for? It gets ugly above the surface, however. A very robust EML looks like it's going to be in place across the whole warm sector leading to a stout cap. The past several runs of the GFS have shown it barely eroding and significantly strengthening after 0z. Midlevel temperatures look sickly warm leading to dismal mid level lapse rates and cape except south of OKC where the richest moisture is bumping cape up to 2000 J/kg. The cap looks menacing even with a good source of lift, and that's our next problem. Both the ECMWF and GFS are holding that trough back over the southwest until it ejects overnight across the plains. Without that upper level support, and the strong cap, it's probably going to be a nice sunny day across much of the plains, and maybe a stormy night over areas to the east. North of OK into KS and the upper midwest, the dryline takes on a northeast to southwest orientation along the elongated area of low pressure. Shear profiles are less impressive as is instability and the EML extends even to the northern reaches of this region. I'm not seeing much of a chase at this point, but am throwing this forecast out here as this setup looked huge a few days ago. The timing on that trough seems to be the main culprit. Without it ejecting over the plains by Sunday evening we just won't have the height falls, colder temps aloft, and lift for a major severe weather event. We'll see what the NAM says tomorrow morning, but if it holds the trough back to the west like the GFS and ECMWF are currently showing, we probably don't have much of a chase setup.

 

[Bob Hartig]

Skip, as always, you've offered a great analysis--cuss the luck, because I had my my fingers crossed with this one. It's been disappointing to watch it degenerate, but that's how it goes with long-range stuff, and the flip side is, the picture can change considerably between now and then. The present run of the NAM looks like maybe the energy could arrive a little earlier, but that's probably just my own wishful thinking, and the NAM trough is flatter and less vigorous than the GFS and Euro.

CINH is clearly a huge issue. The one place where instability and a breakable cap juxtapose, over in extreme southeast KS/western MO, is kind of weird. A quick, random TwisterData point-and-click GFS skew-T for 00z shows low-level winds off to a great start, but then the whole shebang just dies out around 700 mbs, so anything that actually managed to pop up that far east would quickly strangle itself.

I'm just rambling here for the sake of discussion. Realistically, the picture looks like crap right now, but it's by no means a write-off at this point. I'll give it a couple days yet before I'm willing to throw in the towel.

 

[Derek Weston]

What a roller coaster ride this system has been to watch on the models, eh? We're finally getting some run to run consistency and the ECMWF and GFS are in general agreement on the placement, orientation, and intensity of a large trough moving into the plains on Sunday. The setup is a far cry from what the GFS was showing in earlier runs, however. At the surface we've got an extremely impressive pattern: 984 mb surface low, 65 degree dewpoints backing up to a sharp dryline with 15 knots of backed surface winds. Wow, what more could you ask for? It gets ugly above the surface, however. A very robust EML looks like it's going to be in place across the whole warm sector leading to a stout cap. The past several runs of the GFS have shown it barely eroding and significantly strengthening after 0z. Midlevel temperatures look sickly warm leading to dismal mid level lapse rates and cape except south of OKC where the richest moisture is bumping cape up to 2000 J/kg. The cap looks menacing even with a good source of lift, and that's our next problem. Both the ECMWF and GFS are holding that trough back over the southwest until it ejects overnight across the plains. Without that upper level support, and the strong cap, it's probably going to be a nice sunny day across much of the plains, and maybe a stormy night over areas to the east. North of OK into KS and the upper midwest, the dryline takes on a northeast to southwest orientation along the elongated area of low pressure. Shear profiles are less impressive as is instability and the EML extends even to the northern reaches of this region. I'm not seeing much of a chase at this point, but am throwing this forecast out here as this setup looked huge a few days ago. The timing on that trough seems to be the main culprit. Without it ejecting over the plains by Sunday evening we just won't have the height falls, colder temps aloft, and lift for a major severe weather event. We'll see what the NAM says tomorrow morning, but if it holds the trough back to the west like the GFS and ECMWF are currently showing, we probably don't have much of a chase setup.

Right. Timing isn't very good right now. Our low level goodies are too far east out in front of the upper level support. I'm not impressed. Won't leave Iowa if the GFS verifies. However. . . model pattern recognition tells me that I've seen this before. . . and often enough things sync up in the end. Not writing it off. (although trend recently has been downward where chasing is concerned)

 

[Jeff Duda]

Indeed this forecast has gone back and forth in many models (not just the GFS). I've been watching the GFS, FIM, and ECMWF. It wasn't until the 12Z runs today that I first saw them all agree on the pattern at 00Z Monday. The GEFS members are almost split down the middle on the solution that the control member has been going back and forth on over the past few 00Z/12Z cycles (i.e., the neutral tilt trough with strong SW flow nudging into the TX PH and W KS as opposed to the very negative tilt, de-amplified pattern that brings only a strong zonal jet across the central US latitudes, a scenario which would probably result in little severe weather). It's a shame that, for April 2nd with 65+ Tds and 80 degree temps that instability would be so limited, but that's what you get when you have a warm layer aloft like what is progged. Not only that, but the disturbance giving rise to this threat is in such a pre-mature state that it is majorly slanted so that there is very little overlap between the good mid-level flow and the low-level flow. That's just plain disappointing. It is still 100 hours out, so perhaps these elements will come into better focus as the lead time decreases. You have to keep an eye on these things until the day they happen because the devil is in the details and some minor alterations to this setup could result in a much different outlook.

 

[Marcus Diaz]

Well, my hopes are getting slimer by each run. Latest 0z run is still showing timing issues. The main trough may not peak over the Rockies by Sunday. The winds above the H5 look terrible, with perhaps some ridging over AR. Our issue of the dry 850s hasn't popped up as bad on the latest run, but still an issue. There's a weak spot of CIN in SE KS, and CAPE is up to ~1,000 j/Kg in the warm sector. Sfc low setting up on the KS/CO border, which is a good thing. But as mentioned earlier, its all about the timing. If the jet can't get there, we're screwed. 0z NAM is showing the trough a tad further east than GFS for 12z Sunday...so perhaps not all hope is lost. This definitely looks like a day where we won't know exactly until the night before, or even the morning of. Very frustrating...but then again it barely the first day of April