3/20/11 FCST: OK/KS/IA

[Skip Talbot]

has anyone else noticed the changes in the intensity of the surface low.

I have and the weakening trend continues. The GFS was indeed too fast, and is now delaying the arrival of the trough which is negatively impacting everything in the setup from moisture return, surface low strength, to speed shear. What looked like a potential plains outbreak is now a very marginal setup. Mediocre surface winds, marginal instability, capping issues... I'm really losing faith in this one. The GFS is coming into line with the NAM too so the surface features are shifting more south. Looking at the trends here, I wouldn't be surprised to see Sunday cap bust. Its also definitely taken the "day before the day" position, but to be honest, Monday doesn't look that great either, also suffering from marginal instability and capping issues.

At best I see some isolated severe reports where that dryline bulge winds up. Maybe south central KS/northern OK. When the cap fills in after 0z its game over, even if storms have initiated as the diurnally dependent cape is going bye bye and that stout cap is going to force anything that's fired to go elevated.

The GFS dangle another carrot out there and then slowly chips away at the setup until it looks like junk. Bring on April!

 

[Greg McLaughlin]

The last couple of runs of the GFS have definitely been showing a less than idea severe weather setup for SUN and MON. The RH plots also shows quite a bit of high-level moisture (possible cirrus deck) over the warm sector which would likely inhibit good surface heating. Beyond this system, the GFS has been trending toward dropping a massive surface high into the mid-south by next week's end. As a result, a strong cold front looks to rake the Gulf and wipe out the moisture. It may be mid-April before we have a real setup to talk about.

 

[Kelly Sugden]

Meh, I'm a bit more dubious now than before. Saturday looks like elevated convection across Kansas with not much of a severe threat, if any. Still concerned about the cap Sunday, although I do agree with others that models have been overdoing the cap and underdoing cape this season. Monday looks a little better with mid level cooling and stronger flow, however the severe threat maybe well northeast of Dodge so not sure about chasing feasibility or targets now at this point.

 

[Doug Drace]

I agree with with everyone else on here about the declining outlooks for 3/20-3/21. However, there's still some potential, and we haven't been able to go on a chase anywhere so far this season due to some unfortunate and ill-timed medical issues. On that note, unless things just completely crap out over the weekend, we certainly plan to chase either sunday or monday...with a slightly higher confidence of chasing Monday 3/21 with a little better Upper Flow and Cooling Aloft. If things start looking better CAP-Wise on Sunday, we will go ahead and take a shot both days...with a somewhat broad early projection target area from NW Oklahoma into the Panhandles and up into the southern-central Kansas area. Our last Tornado was May 10th, 2010....so waiting around for a Great Setup just isn't something we have the patience to do at this point, and we dont enjoy chasing east of I-35 So good luck to everyone that does end up chasing Sunday or Monday...at this point just an Isolated Sculpted Supercell would be satisfying enough for March...maybe we'll see you out there! There certainly will be better Severe Days ahead...but the worst thats gonna happen will be a nice road trip for a day or two in the magnificent Southern Plains...

 

[Jeff Passner]

Not much argument with what others are saying. There's a general increase in 700 hPa temps on Sunday. The WRF is far more agrresive with the mixing of the dry air coming in from the southeast USA, but the dew points in the Gulf are not exceptionally high to start with and I see dew points in the 40s across north Florida currently. I would not be surprised to see serious moisture issues along the dryline. It's not just the surface dew points but the depth of the moisture. The TLH sounding this morning was bone dry (pw=0.76 cm). Even KCRP had a low precip water of 1.71 cm. There's still plenty of time to watch this system but I agree with others that the Gulf of Mexico is not "ready" yet. Brett Roberts points out that the trajectory in other early-season events was more southerly off the Gulf and it's a good point. We'll see how this system evolves over the next 2-3 days but for now my reaction is to skip this system and save my time, money, and energy for later in the season.

 

[Steven Howell]

Sam, I was just looking at the 00Z NAM run, and there looks to be some potential in the eastern Texas Panhandle, up into Central Kansas about 6pm on Sunday. Its not the greatest setup, but there is decent CAPE, with minimal CIN. The only thing I dont like, is that there is not much in the way of helicity....I do like the look of the dryline though, because it looks like there will be convergence along the dryline and that could be just the ticket to initiate convection into these areas. I dont know, I know there will be better setups in the coming months, but this might be worth the trip. I am thinking of a target area NE of Amarillo, to possibly S Central Kansas

 

[Skip Talbot]

I'm scoping out southern and eastern Iowa here and am not real impressed the past couple runs of the RUC and the 12z NAM want to burn the cap off at around 5. We'll have lost most of our good heating by then so low level instability plummets as a result. Lots of mixed layer cape still being plotted though. This makes me think we're going to be dealing with elevated storms in this area. There's also what looks like a very potent shortwave forecast to move through with a surge of 70 knot midlevel winds. This should provide more than shear and maybe some lift to fire storms off in the early evening and maybe even some supercells. I'd expect a few elevated hailers across portions of Iowa, and wouldn't be surprised if there no tornado reports given the largely elevated instability and that the surface winds are veered pretty badly. I'm keeping an eye on this one but I'll probably wait for Tuesday at this point.

 

[Matthew Piechota]

I'd pretty much agree with Skip's thoughts here. Just looking over the newest run of the HRRR..it wants to break out a broken band of decent looking storms in central IA around 21z with 2500 j/kg of SBPCAPE to work with south of DSM. Even if we were to get those numbers later today (it is already clearing nicely in southern IA) the fcst sfc inds are veered to crap ahead of the front.

The 12z RUC was showing the same thing with bad sfc winds into IA and even westerly 850's all th way to IOW by 0z. The only shot on the RUC would be something in extream eastern IA maybe near DVN on the nose of the instability/theta-e axis where you getting better sfc winds/low-level turning.

Keeping an eye on it but will most likely sit this one out and hope for some storms here later today.