4/5/10 FCST: NE,KS,OK,IA,MO

[Matt Grantham]

There are a few folks talking about a "breakable cap" with this system. There are some huge question marks with this setup. The sounding posted for Newton, KS has a pretty nasty inversion. I highly doubt that a cap like that could be broken in this situation. With the trough and embedded shortwaves hanging so far back to the west, there is hardly any forcing or large scale ascent over the region. Sure...that cap could certainly be broken if you had a the trough axis much further east with good diffluence/divergence overspreading the Plains...but that ain't the case here.

Another concern is surface dewpoints. Is anything in the 65 or higher category achievable? Most if not all of the soundings posted show dewpoints of 65 or greater and in some cases as high as 68. Mike is right, the NAM has to be right about this or its going to be a dud. Knock those dewpoints down 3-4 degrees F and there is quite a bit more CIN. Combine that with the lack of forcing, and we'll have ourselves a nice big bust on our hands.

This really is an all or nothing type of situation. By Sunday afternoon/evening, we should have some idea of what's going to happen with the dewpoints. If these 65+ readings can be achieved along the dryline on Mondaay, then its game on. This is a tough one....

 

[Mark Blue]

Well if we want to post good looking forecast soundings, these two work well...

Concordia KS 7pm

Hebron NE 7pm

NAM needs to be right on this one so bad.

Scary shear in se IA....FFL whatever that is.

I think you're on to something there H. Looking at the 12Z run of the NAM for 0Z on Monday it seems the best ingredients are all coming together right in that area in northern Kansas and southern Nebraska, say anywhere from about Red Cloud east to Hebron and similar locations just to the south in Kansas. The dews look to be at least 60 if not higher, EHI numbers are maximized right in this area (6), just enough of a cap to let things percolate but not strong enough to spell bust, CAPE numbers are looking solid at or above 2000 J/kg (may be a bit overdone on the NAM), shear looks good with helicity values somewhere around 300, all in all a decent looking setup at this time. I think KFFL is Fair Field IA, but I'm not sure where that it to be honest. Maybe some of the IA chasers like Jeff Duda can clue us in.

 

[Mike Hollingshead]

http://www.wxcaster2.com/CENTRAL_MESO-ETA_1000-500_SLPPRPTHK_60HR.gif

It is getting funny how that is the only area it wants to give any precip to between 7pm and 1am. Yesterday 18z same, 0z last night same, 12z this morning same, 18z today same....with just a very small change in location...very.

When I think of this chase I think of something like May 10, 2005 happening. Looks like cap will win all day into the evening then bam, around 7pm high based sup forms near Grand Island.

http://www.wxcaster2.com/CENTRAL_MESO-ETA_850_GPHTMPWINDRH_48HR.gif

I always hate seeing that bad of veering at 850mb through the day. Probably help cook out some dews for a while before backing later on. This might not be a massive issue with moisture wanting to pool near the front though.

 

[Jayson Prentice]

I think KFFL is Fair Field IA, but I'm not sure where that it to be honest. Maybe some of the IA chasers like Jeff Duda can clue us in.

KFFL is Fairfield, Iowa which is located along the E/W Highway 34 in southeast Iowa. Google map link below for reference:

Google Map of Fairfield, IA


Tuesday does have some concerns, given the NAM is likely forecasting dewpoints at least a couple/few degrees to high giving you lower 60s Tds along the warm front and triple point. This will aid in an increase in inhibition over the area with the temperature inversion ~850hPa. Despite all of this I think the one thing that is scary is the lack of mid and upper level support with the main trough and any shortwave well west at the peak time for initiation. There are many mesoscale factors, especially with any remnants of morning convection, that could play into initiation of storms along the dryline and westward extent of the warm front.

I won't be out due to work obligations, but will still keep an eye on things with it being in the vicinity. I don't see any reason not to take the risk though given some of the hodographs and parameters that have been posted above.

 

[Adam Lucio]

The 18z nam quickly develops an inversion layer after 0z and strengthens the cap, which is causing it not to break out any precip...not sure what to make of this.

We go from this beautiful scenario right here

To this nasty one here in a matter of 3 hours.

You hate to see a potentially explosive setup go to waste like that...but what I really think is going to play a major role is Sunday nights convection moving across the area. These warm front days are so finicky it will come down to last minute mesoscale details the morning of...its too hard to pick a target now so I wont stress about it till the morning of.

 

[Darrin Rasberry]

This was a pleasant surprise for me, as I'm still in the middle of a semester and won't be able to chase outside of where I can go after my last class and office hours. I don't really keep up with things before May 6 if they're outside the neighborhood, so I nearly choked on my Shiner when I saw Iowa covered with the SLGT on today's outlook.

My excitement was kind of short-lived, however, since a quick look-see at the models showed that there was no punter in the vicinity to kick this thing off, at least nowhere east of the NAM's crystal-ball storm around the triple point.

I'm still trying to study how outflow boundaries work in specific setups, but maybe we'll get lucky here in C IA with a leftover stain from a Sunday night hailstorm's streak across the carpet. Regardless, I'll still go and hope the loaded gun will fire while expecting not much more than a tan. Initial target: Lamoni, IA. Setup Time: 3PM.

 

[Adam Penney]

Well, it looks like we might have just gotten some good news(for those of us wishing for the dryline/warmfront interection play). According to the 0Z NAM, it now looks to me like the dryline is now progged to be further west, over better upper air support, and somewhat cooler 700mb temps. The CAP looks to be almost completely eroded across the dryline in western KS, all the way down to the eastern TX panhandle at 0Z Tuesday. Shear and EHI parmeters look very good in western KS as well. IMO, this is the best run weve seen today atleast.

Hoping something simliar to this picture being painted by tonight's 0Z NAM, verfies.

 

[Jeff Snyder]

Well, the thing that gets me most "giddy" about Monday's possible event in Kansas is the shape of the hodographs. The 00z NAM from this evening continues to show a rather beautiful "sickle-shaped" low-level hodograph (with a straight-line segment above that) in much of Kansas east of the dryline. Even for areas farther south into Oklahoma, the low-level portion of the forecast hodographs is gorgeous, though there's some possible issue with very weak (almost nonexistent) shear between 3-6 km. The 21z SREF has mean 0-1km SRH >250 m2/s2 E of the dryline across a good portion of Kansas and parts of northern Oklahoma at 00z Monday evening (that is, 00z Tuesday, technically). Of course, the areas in eastern KS and OK have strong capping, by and large, so it's not terribly surprising to see these two characteristics (greater low-level stability / capping and stronger low-level shear) juxtaposed.

The hodographs farther north and east along the warm front are very long, particularly in the low-levels, which is another good thing to see. For the area that had my greatest attention on previous runs (that is, the area I liked around CNK), the latest NAM is keeping temps cool, which means a very stable low-level environment. I haven't paid much attention to areas farther east into IA/MO/IL since I'm not going to chase in those areas, but they look interesting as well.

The real juice is still hanging out in southern Texas, with the >60F Tds southeast of a line from Alexandria, LA, to Austin, TX, to Del Rio, TX. VWPs from area radars and profilers are showing SE to SSE winds below 2 km AGL at 25-35 kts attm, so we should have plenty of time to advect pretty good moisture northwards to the warm frontal zone by Monday afternoon.

The GFS and NAM seem to be off a little in terms of the areas that may see the depletion of CINH, but both models are forecasting at least some areas in KS to have only very weak CINH by 00z. The 21z SREF is "only" showing a >10% (but <50%) prob of precip ahead of the dryline by 00z (see HERE, time sensitive), with very little in the way of 700 mb UVV as the primary trough aloft (and associated vort max) remain a considerably distance to the west. I think we may need to hunt out those subtle shortwaves that can emanate from deep troughs like this one...

I don't want to spend too much time talking about models, so I'll just reiterate my "highlight" that is the hodograph forecast... It looks like a definite MDT-risk day, though some question about initiation may limit convection coverage in OK/KS.

 

[Greg McLaughlin]

Deep moisture return is now underway. I have been paying close attention to the soundings along the Gulf coast to see what kind moisture depth we have. I am pleased to see high dewpoints (>15c) up to 850mb on CRP sounding! Surface dewpoints are in the upper 60s to low 70s in deep south Texas which is quite impressive.

 

[Chris Wilburn]

Deep moisture return is now underway. I have been paying close attention to the soundings along the Gulf coast to see what kind moisture depth we have. I am pleased to see high dewpoints (>15c) up to 850mb on CRP sounding! Surface dewpoints are in the upper 60s to low 70s in deep south Texas which is quite impressive.

That is quite impressive indeed. Hopefully the mid 60 dewpoints make it well into KS. EHI and SRH at all levels are insane along the dryline in KS, triple point in northern KS and the warm front along the MO/IA border. The one problem I noticed on last nights 00z run of the NAM was the best 500mb vorticity was still west of the rockies. It looks like we may need the help of a shortwave to kick things off. With all of this said things look very impressive with all of the parameters I have looked at. The EHI and SRH values are actually some of the best I have ever seen for Monday. Lets hope capping and lack of upper level vorticity don't ruin an otherwise very impressive setup. This mornings run of the NAM and for sure this evenings 00z run should paint a better picture on what to expect on Monday. Hopefully it gives us something to cheer about because I am ready to go. I really hope the dryline in KS or triple point in KS start to look appealing. I am willing to drive to the MO/IA border to play the warm front there, but have never chased that area like KS and am unfamiliar with it.

Well the 12z data is out on the NAM. It appears along the dryline in KS and along the warm front along the IA/MO border has less CINH that last nights 00z run and the 06z run. The hodograph for north of St. Joseph, MO near the IA/MO border is nothing short of textbook. I might add that along the dryline in KS say near Hutchinson is near textbook as well. Dews forecasted mid to upper 60's in both areas with CAPE near 3,000 J/kg and close to 4,000 J/kg in an area along the dryline in KS. EHI and SRH values to continue to be off the charts, esp. the 0-3 SRH and 0-3 EHI values in both locations mentioned. Dryline in KS, triple point in KS and warm front along the IA/MO look very nice. Somebody please add something if I am missing anything. I still have some CAP concerns along with the best 500mb vorticity being way west of the best parameters.

If any storm can get going it will be very explosive in it's development. I remember the Greensburg day had similar parameters. We started heading back to Wichita and about an hour before dark cells started to explode and quickly went tornadic. After this day I have learned to never give up on initiation late in the day.

 

[Skip Talbot]

I'm digging the 12z NAM run. The NAM has been quite consistent in the amount of instability, the position of the surface features, and the location and strength of the mid level flow since this setup came up. One real nice trend I'm seeing is a weakening in in CINH over both the warm front and the dryline as the setup draws closer. Since watching this several days out on the GFS I have been torn between the triple point/dryline target and the warm front target. Both areas have ridiculous hodographs that scream tornadic supercells, ample instability, and plenty of speed shear. If anything the 12z NAM is making me lean more towards the warm front target in SW Iowa/NW Missouri. The cap looks like its going to erode nicely by 0z and the NAM is even breaking out precip between 0z and 3z. This is after dark which is discouraging in itself, but for most of the previous runs there was not much precip at all forecast to break out. I think the key might be to watch the mid level flow the morning of the event and see where any shortwave troughs are. These will likely be a focus for initiation later in the afternoon/evening. Also if there are any outflow boundaries left in the wake of morning warm front convection, this might also be a focus of initiation. I'm probably going to leave tonight from Chicago, and stop overnight in SW IA. Checking morning data I should be able to hit either the KS triple point/dryline target or a warm front target to the east, as initiation isn't forecasted until the evening anyway. The morning of I'll have a better of idea of what the cap is doing, where the shortwaves are, and if there are any secondary boundaries that will aid initiation.

 

[Greg Blumberg]

I'm happy with the current setup. My main concern is the placement of the warm front, which I'm not trusting at all where the GFS or NAM places it. If anything, I'm going to try to hang back in Wichita, KS and watch the observations, then refine the target once something catches my eye. Mesoscale details will be essential to identify in a situation like this. Hand analysis for me tomorrow morning!

The wind profiler network will be essential in helping spot any possible shortwaves or small jet streaks moving through the area. A situation like this where shortwaves could be the make or break thing reminds me of the May 3rd, 1999 scenario where the wind profiler network picked up the upper-level dynamics necessary for that day.

Otherwise, my main excitement right now is the existence of near 70 Tds already in South TX and already here in Oklahoma we're getting southerly flow. I just hope this can really crank up come tonight and tomorrow morning. Any little bit more of moisture will help our situation and possible cap concerns.

I have no idea why SPC is being so persistent in downplaying the potential compared to what I'm hearing on this thread. Does anyone have any thoughts to that?

 

[Tony Laubach]

I have no idea why SPC is being so persistent in downplaying the potential compared to what I'm hearing on this thread. Does anyone have any thoughts to that?

Truthfully, I am baffled.. SPC's 1730z came out and removed even a general thunderstorm threat from the dryline... EML and cap don't look THAT strong. I understand the concern over the upper level dynamics still being back west over the Rockies, but I thought there is enough convergence along the dryline to at least warrant some precip chances. Are we (or at least I) that wishfully thinking? Seriously, I would be delighted if someone showed me this key piece that is destroying the KS target.. I can't find it... my ignorance is having me step out to say, please someone, show me the ways! LOL

Actually, I am going to reword my plea to slightly revise a quote from one of my favorite movies...

"Ray... for a moment I don't know anything about Meteorology, Atmospheric Dynamics, or Physics... and just tell me what the hell is going on."

 

[Scott Weberpal]

south-southwesterlies bumping up against southerlies doesn't exactly scream fantastic surface convergence. If the surface winds ahead of the dryline were a little more southeasterly, my hopes for something popping there would be a little higher. The only exception is alone the DL bulge, but up there the sfc winds are weak sauce and convergence is quite shallow.

Sure, CIN is essentially gone by 00z, but the mentioned lacking surface convergence and pitiful upper support will go a long way in making this a likely non-event, at least along the DL.

 

[Darrin Rasberry]

Anyone notice how the 12z GFS broke out precip in SE IA (along the WF) between 21z and 00z?

The 12z 4km WRF puts precip over SE NE at around the same time, but it looks unhealthy over the entire timespan that it exists. Looks like a few spotty showers for a few hours, and this is in the warm sector. Dunno what this means.