4/10/08 FCST: OK/TX/MO/AR/KS/TN/IL/KY

[Derek Weston]

Call me crazy...but isn't most of the shear of Missouri uni-directional or darn near it? That's what the NAM says.

I just don't know about tornadoes. Lots of severe weather, no doubt, but maybe we'll have major line segments as the principal mode.

A little further east into Illinois you get a bit better directional shear, and then down into Arkansas, that looks a little better too. Though nothing like the setup we're about to see on Wednesday. (which looks much better for tornadoes to me)

I guess speed shear might contribute somewhat to the potential for tornadoes here, but I'm rather skeptical of most speed shear setups. (I know we sometimes get decent setups in speed sheared/low direction shear situation...but it seems to be the exception rather than then norm)

 

[Kevin Askew]

This is setting up to be a night chase for us in SE MO. area. Will set up somewhere from Bootheel to Sikeston as of now. Best energy making it in according to SHREF after 2100 thursday. We shall see but we bankin on SEMO right now

 

[Brandon Sullivan]

Thursday..

00z Data

WRF
The NAM continues to show a Strong Negative Tilt with the system, lifting the Warm Front Northward into western IL, northern MO by Thursday evening.. It appears it is taking the warm front further north than with previous runs, according to a quick run through Dprog/DT... The NAM also brings almost 2000 J/Kg CAPE into Central and Northern MO at 00z Friday. With some 60 degree DP's moving into the region.. Also, it hints at some drier air working into the H8 layer which could prove helpful. Although the GFS is not as aggressive with the Instability in the area, the NAM does show Showwalters Dipping into -2.,

GFS
As mentioned above the GFS is less aggressive with Instability to the north. but takes nearly the same path as the NAM, being slightly further east.... It also shows some impressive H5 vorticity values. Again, I like the drier air working into H7. Any breaks in any clouds would be great, and would help destabilize the area... The GFS also shows an impressive LLJ really maxed around LSX to LOT line...

Both Models
Both really crank up this system with a nice LLJ as it deepens, breaking out precip across the warm sector..I wouldnt be surprised to see some NNW shift/expansion to the SWODY2 ( which I usually eat my words when I say something like that) Looking at the 00z GFS/WRF Low And Mid Level Cloud comparison, both models indicate pretty good cloud cover with the potential for some breaks maybe in Central/Northeast MO, likely due to the aforementioned drier air.

Target
I don't want to pick a target yet, with such a strong/complicated system.. But needless to say, a very dynamic system, and very much worthy of the attention it is getting.

 

[Ken Johnson]

Thursday

I wouldn't rule out NW Mississippi on this one either. Chase terrain is very good here and dynamics/thermo look good. NAM Bufkit data does show the cap breaking with 454 Helicity and nearly 1600Joules of SBCape. Could get violent.

 

[Jesse Risley]

For those of us on the northern edge of things, at this point the setup looks more conditional. I'm impressed with the forecast moisture return at the northern edge of the system behind the advancing warm front, as well as the very favorable shear profiles.

However, I think the extent of the northern play will depend on whether or not the dry slot indicated on recent model runs actually verifies following all of the morning convection (SB CAPE could exceed 1000+ J/KG), possibly lending to adequate atmospheric destabalization. If this does verify, the area between I-70 and I-72/U.S. 36 looks to be a good bet.

EDIT: If aformentioned strong forecast dynamics remain unchanged, I can see the marginal instability (CAPE 500-1000 J/KG) concern being overcompensated for by very favorable shear profiles and more than adequate moisture return.

 

[Andrew Pritchard]

Here on the north end I'm interested in the area around the IA/MO/IL junction, probably more so NE Missouri and WC Illinois. Assuming the morning, potential day ruining rain gets out of there it looks like we could see decent instability setting in just ahead of the surface low. I think this area almost certainly will see thunderstorm development, I'm just not certain yet if we'll see the airmass recover quickly enough to do it before dark to give us a window for daytime supercells or if we'll end up with a nocturnal screaming squall line.

Upper air soundings for this entire region are very conducive to supercells and tornadoes conditional on how much heating we get. I hate these wait and see in the morning setups, but with such a moisture socked setup that's exactly what we have. The potential is there for a few strong tornadoes in eastern Missouri and western Illinois, but there's just as good a chance we'll be singing (or pouting) in the rain all day.

Also, Scott - he was talking about NW Mississippi, not Missouri.

 

[Brent A. Clair]

Anyone else looking at the 12Z runs seeing a more northerly component? Saw the buckle of the jet in NV at initial hour, and that just pulls everything north. Still not the ideal setup, but slowly becoming. I'm sure my neighbors to the north of me (Jesse, Brandon) are salivating at the prospects, but remember, one model run at a time!
Pritchard, I tend to agree with you on the nocturnal event. Reminds me of March 12, 2006, where the more devastating tornado went through NE Mo around 9:30-10:00 at night.

 

[Karen Politte]

The 12Z models seem a little faster now with this system, ejecting the deepening surface low associated with this trough from northern OK by 12Z tomorrow and placing it in NE KS by 18Z. This could be a good thing, as it may shift our area of highest interest into the more chaseable terrain of eastern AR.

Speaking of eastern AR - does anybody have a reliable map of highway closures due to flooding? The map on the AR state highway website only shows one road in the whole state as being flooded - but it's such a general map I have very little faith in it being accurate. I know from reports that some smaller roads east of Little Rock are closed due to water covering the roadways.

KP

 

[Kevin Crawmer]

March 12, 2006 had some convection the previous night/morning, but things cleared very quickly that day and CAPE was around 2000 over much of MO. It does remind me of that setup, but I think there was a lot more instability over a bigger area that day. I do not remember how directional the shear was. Going back in the SPC archives the Day 2 out look on 3/11/2006 looks very similar to today's.

I still think it may evolve into a widespread event with the bulk of the in MO/AR during the day and into IL/KY/TN into the night. I have a feeling that things will get popping down south most of the morning and wouldn't be suprised to see isolated tornadic storms along the warm front early in the day if there is any clearing at all. By 1pm I would guess storms would start popping off the dry line in areas in SW MO/NW AR and become more widespread in the afternoon. The shear, instability, and moisture should be primed for a big outbreak of tornadoes tomorrow in Eastern MO/AR and into IL/KY/TN. People in St. Louis, Cape Girardeau, Memphis, Paducah, Springfield,IL, etc should all be on their toes tomorrow afternoon and especially during the evening hours.

Preliminary Target: Set up in Lebanon, MO by noon...move to the area of best instability from there.

 

[beaudodson]

Paducah is having a conference call at noon. This looks to be an intense outbreak for my neck of the woods. I am hoping we don't see another bad tornado event. I have to work the outbreak with emergency management, so I won't be chasing it. Looking at the soundings for KPAH makes me wonder where the second round will form on Friday Morning. KPAH still has decent CAPE as late as noon on Friday. I am thinking we see some supercells across southeast Missouri and eastern Arkansas that will move into southern Illinois and western Kentucky on Thursday evening. Then a squall line after that. Good luck to everyone who is chasing this region. Be careful - roads are still flooded from the last rain event.

For those chasing in Arkansas - this is from another poster

Karen Politte over at StormTrack was asking for a map of current flooded roads in Arkansas... I've apparently lost my sign-on info at the moment, but wanted to post this website for anyone who may need it:

While it's not a map, this is a county-by-county listing of closed roads due to flooding in Arkansas:

http://www.adem.arkansas.gov/

Click on the red banner running across the top of the screen and scroll down to TRANSPORTATION (about 1/3 the way down). It was updated today (the 9th).

Johnnie Gambill

End paste


Beau

 

[George Limpert]

An MCS will develop over the Southern Plains tonight and will track northward as the warm front rapidly retreats through the Ozarks and through northern MO. My thinking is that there will be two waves of convection. The first will be as the warm front moves through central MO with possible supercells on the southern edge of the MCS. That looks to move through central MO late in the morning or early in the afternoon. As the clear slot moves in behind the MCS, relatively weak instability will develop. I expect the second round of storms to develop along the dryline over far western MO during the mid-afternoon. Instability will be less than ideal, but the strong dynamics should be strong enough to compensate. My primary concern is how the MCS evolves overnight and tomorrow morning. My initial target is north central and northeast MO.

 

[Ross Lazear]

Wow, you're right Brent, the NAM makes quite a leap in the 12Z run, which would make for a shorter drive from southern Wisconsin. At least from the northern end of things, I also like the IA/MO/IL border, around Keokuk, IA. The big issue still appears to be instability, and whether or not overnight convection will hinder the potential for a pretty impressive outbreak across the (northern) area.

I also have been thinking about the similarities with the 3/12/06 event, though the upper tropospheric flow should have a more southerly component to it across MO/IL/IA tomorrow, unlike 3/12/06. I remember that supercell that formed along the WF in west central MO, and moved ENE to NW Indiana by midnight, producing a very long track tornado from Bowling Green, MO to Springfield, IL.

Good luck, all!

 

[Brent A. Clair]

Just for clarification, the fact that the storms are nocturnal in nature was why I mentioned 3/12/06. I had not done any comparisons on the UA features, so I have no bias one way or another if there is a comparison.
Now then, after running the 12Z BUFKIT, it finally starts to pull in the instability to the triple point of IA/IL/MO by early evening. The only fly is a little too much cloud cover when heating is needed. But, we have had our biggest outbreaks when the majority of the day was cloudy, so as long as the upper levels get their warmth, we're good to go.
Nice to dust off the forecasting tools again and make a perfect bust!!!
Later

 

[Scott Weberpal]

Given the eastward trend of best deep-layer shear and instability, I'm becoming more confident that W. IL could see tornadic supercells during daylight hours. The question always remains, do you head into MO or wait for the storms on the east side of the river? Both have their pros and cons. I will likely stay on the IL side of the river given fast storm motion, and given that any storm that moves into IL between 21z and 00z will have the best environment to work with. Quincy forecast sounding is amazing!

 

[Mike Johnston]

As things stand right now, however, April 3-4, 1974 is probably the closest comparison I can come up. Although I haven't had the chance to make a detailed comparison, a quick glance shows interesting similarities between archived maps for 00Z 4 April 1974 and this morning's NAM forecast for Thursday evening.

Yes, a brief read through the NOAA technical report (http://www.april31974.com/TornOut.pdf), is fascinating. There are quite a number of similarities in the synoptic maps for the 36 hours leading up to the afternoon of April 3, 1974, and the forecast charts preceding this event. One key difference, I notice though, is that there was a significant inversion w/ very dry air @700mb across much of the warm sector on 4/3/74. This helped to keep a healthy cap in place as the instability built up, and when convective temps were reached, the release of energy was sudden and violent. In this setup, I see extensive swaths of relatively humid air @700mb, and there isn't much forecast CIN except on the eastern fringes of the broad target area.

Even so, the dynamics look almost incredible on this setup and it is hard to envision how this will not be a fairly widespread outbreak. Probably will not actually reach any of the records of the Super Outbreak; the overall system is very similar in profile, but not quite as potent. However, I wouldn't be at all surprised if Thursday turns out to be the most significant tornado day of the year.