2009-05-12 FCST: KS,NE,MO,IA,IL

[jamesmseitz]

I have been watching this system for about a week and I think it is the one to watch. On Tuesday, the system seems to want to come out of the Rockies into the Central Plains then through the Upper Mississippi Valley on Wednesday. Moisture return, shear, and strong heating ahead of trailing front that will stretch from the Canadian Border to the Central Plains. Along this feature, it seems to have at least one major impulse that will feed the gulf air into this unstable environment. My belief is this will be the first outbreak in the area since last year.

It seems to have all the earmarkings of a major outbreak. I've never started one of these so I'm very interested in what everyone has to say about this set up.

 

[John Hudson]

I have also been watching Tuesday's GFS, with interest. Definitely ample moisture in place, and shear shouldn't be a problem, although surface winds are going to be pretty modest.

The cap looks to be like it could be a significant problem, even with good heating in place, until you get into NW KS/SW NE. Here it won't be as much of a issue, and there's a sharp dryline that could make for an interesting play.

It will be interesting to see if the northern extent of the moist axis verifies.


John
VE4 JTH

 

[Eric Bucsela]

It's now 120 hr from Tues evening, and we're getting into the time when the medium-range models are "relatively" stable - on the synoptic scale anyway. GFS and ECMWF are in consensus bringing a strong wave into the northern plains. Latest run (May 8 00z) of the ECMWF is stronger than the previous ones and gives it a nice negative tilt.

Superficially (to my eyes) it looks a bit like last April 29. Both models agree on a mid-level jet curving from northern Utah into the eastern Dakotas, a surface low near the KS/CO border, and a decent low-level jet through KS. Relative to Apr 29, the GFS is predicting slightly lower dews, but a deeper surface low and stronger h5 winds in KS. But this is way too much detail for a 5-day forecast.

Anyway, the better h5 winds and weaker cap are in NEB, and this could be a good target if the moisture gets up there. Otherwise, as on Apr 29, the winds in KS and into the panhandles may be enuf for some good storms if the lid is not too strong.

What do you all think?

 

[Adam Lucio]

I have been watching this as well with an eager eye.

I posted a more detailed forecast on my blog which is linked through my site.

What I like is the fact we have a deeper surface low than what weve been getting lately. This will up the forcing and may help break tha cap which looks to be very stout...especially along the dryline as it extends south through KS and OK. Moisture will be there but also surface heating looks strong further south which may still lead to a high spread and higher based storms.

Im sure this will change though but the consistency in the runs has been a good sign thus far. I will be curious to see what the NAM says once it gets in range.

 

[Jared Farrer]

ECMWF has a deeper trough but its somewhat similar. Which is kinda a good sign I guess! GFS has moisture issues though, which is concerning. I am pretty, sure though that there will be alot more instability if and when it comes. I am liking it so far. Let me just say, that lately the GFS has been on crack. So I havent been really taking it to seriously!

 

[Andrew Stoller]

This system looks to be pulling on A LOT of hot dry air from the southwest. 15-17+C 700 mb temps, where the best instability looks to setup up in western KS. That could be a serious fly in the ointment. Looks like precip would only break out much further north where the better upper level lift/dynamics are at this point, but where there's no instability. CIN goes maxed out to -900 after 00z!

 

[Brian Stertz]

Tue. 5/12 looks like the setup day across the C/S Plains and High Plains areas....especially if the system is a powerhouse and slower to progress east. I like both Tue. and Wed. for supercells across NE/KS/IA/MO/MN where better forcing and less capping will be in place. Certainly one to keep a chaser eye on. Seems like we are dealing with disjointed and slightly out of phase systems this spring so far. Just wondering when this pattern will switch....

 

[Jeff Passner]

It looks like a simple cold front type of event to me. Tuesday looks very capped in Kansas with the most likely convection in Iowa and Nebraska on the cold front. There are some significant pressure rises behind the front so I doubt the front will stall or slow down much. There might be a line of storms into Oklahoma on Wednesday, but in general, these cases bring hail, wind, and sometimes isolated tornadoes between cores on the line. I don't like the warm temps in the mid-levels, the fact that the vort max races along to the north, and 850 MB winds are veered almost westerly. Surely, there will be severe weather if the models verify but it does not look like a major event or a tornado producer based on the current model output. Obviously, that can change and will with each model run.

 

[Rich Thompson]

I tend to agree with Jeff - I'm not impressed with Tue 5/12. There will be very little time for recovery across the central Plains in the wake of the frontal intrusion now into TX/OK. That front will still be hanging out in TX early Tue, so I don't believe any reasonable moisture will make it very far N. If you've watched the trends in the GFS with its surface Tds, they've gone down 5-10 F in the narrow warm sector during the past 48 hrs. That downward trend fits what I would expect looking at the broader pattern evolution.

The cap will also likely be too strong along the developing dryline given the marginal moisture return beneath a warm EML spreading off the Rockies. The best shot at daytime storms will be along the cold front from NE newd, north of the stronger cap.

Tue is my last day off until late May, but I'll probably pass on a long drive for the outlined scenario.

Rich T.

 

[jamesmseitz]

I did not like that last model runs as well. The impulse that was on the trailing edge of the front is no longer showing up. If this happens Jeff is right. When I posted this it looked like a great dry line with the trailing low. I know (especially GFS) things change all the time but I am thinking (and hopeing) that the front will pick up that low out of the rockies. Time will tell

 

[Jeff Snyder]

The GFS has the surface cold front all the way into southern Texas Monday night and into Tuesday morning. Return flow commences Tuesday as lee troughing develops, but I can't imagine we won't see moisture return problems for an event N of OK and TX on Tuesday. The current GFS has a relatively narrow band of >55 F Tds sneaking up the High Plains, but any more meaningful juice looks to remain south of the OK/KS border. Hopefully, the front won't push as far south as the NAM and GFS are showing for Monday... As it is, it looks more like a TX/OK Panhandle day (or maybe wesern OK) to me, where the LLJ is progged to be rather strong. Unfortunately, the best flow aloft is across the northern US, leaving considerably weaker flow (and deep-layer shear) across the areas with better instability.

 

[John Hudson]

I am also less than impressed with the latest GFS model runs. There was better juice into SW NE where the upper flow was a little better, and the cap (which was quite huge until you hit extreme N KS) looked like it would be just right to let something pop later in the day.

The latest run downplays the plume of good Td's over yesterday, and the moist axis is really struggling to get into KS and NE. What's more, is the cap isn't the issue it was over E OK/TX, which is probably where the first decent storms will fire now (away from the decent shear, as Jeff already pointed out).

Too far south with marginal shear means I'll probably sit this one out, unless things change drastically between now and Tuesday.


John
VE4 JTH

 

[Derek Weston]

0Z continues the disappointing GFS trend on this one...

Mid/upper energy is well off to the north of any respectable CAPE -- the upper plains/midwest would be ripe for a big day should moisture moisture return to the area -- but not holding out much hope for this. As it is... the slim band of decent CAPE projected for Neb edging into SD is well west of the good lower level shear...

Of course... large swath of 10C + 700 temps in the western plains -- where some of the decent CAPE does exist -- makes the CAP a big issue anyway. (kick us while we're down -- eh?)

TX panhandle into W OK might be able to eek out something interesting, but I'm not seeing shear needed to be anything too exciting. (and the looming chance of a CAP bust doesn't help)

Being from the midwest... not worth the journey. Disappointing considering this is a strong system with a large area of favorably sheared territory to work with.

 

[Fabian Guerra]

Looking at the latest NAM run (off hour 06Z) it looks like the area of c/sc South Dakota could hold some good possibilities. It shows backed surface winds, a 40 knot LLJ out of the south, 55 degree dp's (which up there should be enough), and a 60 knot west-southwesterly 500mb jet streak that should nose in that general area in the late afternoon. There should be enough instability as well. It shows a cap but it looks like the kind of cap I'd like to see for this setup...just enough to help make the storms discreet or semi discreet (-100 j/kg).

It's obviously still a little ways out and it IS the off hour NAM run but in my opinion its better than anything the gfs is showing for next Tuesday.

Fabian

 

[Skip Talbot]

The GFS and WRF seem to be in agreement that 55 degrees dewpoints will advect north setting up a dryline and thin axis of marginal instability. Eastern Colorado or western Kansas look good along the I-70 corridor where the marginal instability and upslope flow could fire off a few discrete storms with deep layer shear adequate for supercells. The cap still looks like it could keep a lid on everything here, but the WRF breaks out precip at 21z where there is some erosion right on the dryline in eastern CO. I don't know if I could justify the trip given the marginal conditions and probability of a bust, but I'll be watching this one.