4/02/06 FCST: IL/IA/MO

it looks like it could be a decent chase. the upper level wind fields wont be nearly as strong as what we have been seeing so the storms themselves could end up being more chaseable. and i personally liked what the NAM has in southern arkansas better than illinois with LI's of -6, DP's mid 60's, T's mid 70's, 1500-2500 J/kg, and helicity values of 200-300 being forcasted. Its a shame im goin to be chasin turkeys in tennessee instead of the storms in arkansas.
 
It is intetesting to compare this set up to the infamous outbreak of 4/19/96:

Illinois Outbreak

The overall pattern is similar but in the case study, the warm front surges north leading to +14 degree 3 hour dew point changes!

Given the uncertainties of model data this far out, it's something I plan on watching.
 
I'm very concerned for the areas of IL and IN bounded by I-88, US 31, and I-74. The nose of a 500 mb jet streak will be juxtaposed with the TP of a 998 mb sfc low. Sfc winds are progged to be from the SE/SSE, with 850 mb winds from the SW. It looks as though sfc temps of 70° and sfc Tds of 60° should make it all the way up to I-88. Place a diffluent jet stream on top of that area and it just spells great trouble (and, if I'm not busy, my very first chase? B) ).

FWIW, my WFO (the very mild-mannered, unexcitable LOT) is very concerned and used strong wording in their latest AFD (I'm not kidding! Here's the proof).

4:56pm 3/31 EDIT: Central IL WFO really jumping on board, already talking about siginificant severe weather event in their AFD, and a potential conference call in their HWO.
 
I'm a native hoosier, so the setup is obviously a particularly interesting one. I grabbed a few screen-shots from the 12z NAM earlier this afternoon from GrADS, showing some of the better areas I had in mind... Mosey on over here for a look-see.

I have EHI analyses from 21z Sunday (4pm Sunday) and 00z Monday (7pm Sunday), as well as a few other convective forecasting panels from 21z and 00z. I also included a grid-point forecast sounding from near Macomb (probably closer to Fountain Green, IL).

These all point toward northern MO, southeastern IA, and western IL - all areas, I'm particularly interested in with this event. Fairly similar to the March 12 setup, although, with less dynamic support. While shear doesn't seem to be much of a problem, for some reason or another, 18z soundings indicated CAA and subsidence aloft, around the area... Not sure if that'll play a role in some slight strengthening of the CAP, but it could. I also liked the Theta-E advection at H85 over western portions of IL - and if history (and science) proves correct, areas near the apex and to the right of the 850mb Thete-E tongue could spell enhanced tornadic potential if sufficient MLCAPE's and helicities coincide - which don't seem to be a problem either (see the EHI analyses).

Strictly, going off the 12z data (haven't looked at the 18z data very closely) I'd pick the area bounded by Quicy to Springfield to Galesburg, with a target of around Macomb.

Briefly looking at the 18z now, it appears that the NAM has slowed the system down some and is breaking out convection in it's QPF more over IA and northern MO around 18z Sunday. Thermodynamics and instability still look fairly good, however, over the aforementioned area around 00z, only slightly slower than the 12z had. Quincy still may not be a bad option... now that I've looked at the 18z, going westward into IA may be better... where mid-level support is best.

Either way (IA or IL, or even MO), if anyone heads out, good luck!
 
Still waiting for the 00Z GFS but the 00Z NAM would make me want to get to UIN by noon and play from there.



http://www.wxcaster.com/etaskewts.php3?mod...&STATIONID=kuin 45hr (21z Sunday)



Obviously, placement of the low is still in question this far out but that's been my target area for the last few runs and the latest NAM doesn't do much to change that. Will keep monitoring and fine tuning but there does appear to be the potential for a few tornadoes on Sunday, especially early on. Things should go linear by evening and race to the east from there.
 
OVERALL PATTERN AS
CURRENTLY FORECAST BY NAM AND GFS STRONGLY SUGGESTS AN ENHANCED
POTENTIAL FOR LONG-TRACK SUPERCELLS FORMING ACROSS SRN IA/NRN MO AND
THEN MOVING ACROSS THE MS RIVER FROM AFTERNOON INTO EARLY EVENING.
FORECAST STORM RELATIVE SHEAR AND POTENTIALLY LOW LFC NEAR THE WARM
FRONT AND SURFACE LOW...FROM SERN IA INTO NRN IL...APPEAR SUPPORTIVE
OF STRONG TORNADOES IN THIS AREA.

I'm leaving SC around 1PM on Saturday, and will set up around Vandalia, IL for Sunday. I'm from NW Illinois originally, and know the are well. everything South of I-80 is FLAT, So try to stay south of there is possible. I talked to a buddy in Morrison, Illinois, and he said that they are already telling people to monitor weather radios, etc, and that this could be a very dangerous set-up on sunday. It appears that with every new forecast, it becomes more serious than the last one.
 
4:56pm 3/31 EDIT: Central IL WFO really jumping on board, already talking about siginificant severe weather event in their AFD, and a potential conference call in their HWO.
[/b]

Because of the event being on a Sunday, we were trying to give more of a heads-up to the EM's about the possibility. The March 12 event, also being a Sunday, caused some confusion and concern among EM's.

Chris G.
 
I'm liking Sunday more and more. Timing is going to be crucial, on many fronts (no pun intended).

I've been watching this for days, and originally liked the Galesburg, Il. area. That may change in the next 24 hrs, but not by very much. SFC Low looks to be taking a path vicinity of I-80 corridor, but the 2 things that may affect tomorrow are 1.) How far warm front surges. I think best tornado threat will be along and north of front, in western portion of Il. and 2.) any convective debris inhibiting daytime heating from earlier convection from the west. High Risk? If issued, for a very small area I feel. Probably vicinity of Miss. river.

Path of this event is somewhat similar to 5/10/03 (SE IA, NE MO, Western IL).

Thoughts??

Finally will get a chance to chase this year!
 
I'm kind of weary on how much the convection tonight may hinder heating in the western part of the area tomorrow, just as Terry pointed out. The instability should be there if we can get at least a narrow corridor of strong heating (something that Thursday's storm system lacked in KS/NE due to a weak cap). I'll have to look at stuff early Sunday to get a good grip on a possible target area.

It looks like the 1730 Day 2 Outlook is out, and almost all of IL is in the MOD area.
 
I am a little concerned about how the GFS has taken a jog south with the low, but it would seem to be the result of some convective feedback issues. I expect we'll see some supercells in a small window of 3-7 PM tomorrow across SE/EC IA...NE/NC MO and into far NW IL. After that we should see transition to more quasi-linear modes. Parameters as far as tornado potential goes have been steadily falling off in the past few NAM runs when analyzed near possible convection. Therefore, I am becoming less certain about the tornado threat especially if sfc wind field veers more to the south or south-southwest in the afternoon and better mixing occurs which would decrease SRH and increase LCLs...possibly leading to more unidirectional shear supportive of bow echoes.
 
Looks like this may turn out to be a good day..chasing wise. Degree of low-level shear along with
moist-moderatley unstable airmass suggests that several tornadoes will likely occur...a few of which could be strong and long-lived. The area I'm sticking to is still Mt. Vernon - Vandalia, IL. Is the lack of many posts for this thread due to lack of excitement, or just everyone is out and about? btw - it looks like the storms that are moving this direction now, will be out of this area by early afternoon, which should clean out the debri.
 
Well after careful analysis, I have picked SE IA/WC IL as my hot spot for today. Me and my chase partner are going to leave Madison,WI at 8 am and head for the Burlington, IA area. Last time we were close to this location for 3/12/06. All the action stayed to our west that day. This storm system looks just as strong and is taking a slightly more Northward track. I like the temps at 70 and Dp at low 60 range. With the low strengthening as it heads our way the low-level shear will get stronger and I hope the jet streak hits around 3-6 pm timeframe. We should be just SE of the Low. This could make for some good fireworks unless SPC is playing a late April Fools joke on us. I am saying HIGH RISK on next CnvOut for a small area from SE IA/WC IL/NE MO. YES! B)
 
Looks like this may turn out to be a good day..chasing wise. Degree of low-level shear along with
moist-moderatley unstable airmass suggests that several tornadoes will likely occur...a few of which could be strong and long-lived. The area I'm sticking to is still Mt. Vernon - Vandalia, IL. Is the lack of many posts for this thread due to lack of excitement, or just everyone is out and about? btw - it looks like the storms that are moving this direction now, will be out of this area by early afternoon, which should clean out the debri. [/b]


Have a feeling quite a few of the regulars were chasing out in western OK today and are probably sleeping it off by now. I'm pretty excited about the possibilites for Sunday personally. I'm currently targeting an area from COU-UIN-STL. In other words, more NE/E MO which will be a little closer to the surface low and a little quicker to clear out from the morning convection.

http://www.wxcaster.com/modelskewt.php3?mo...STATIONID=_kstl

WRF-NMM breaks out precip around 20z in a line from IRK to just west of COU. It rapidly forms into a solid line on the northern fringe by 22z while the southern portion remains discrete for a longer period of time (if you believe model output of simulated radar reflectivity). Regardless, the combination of insolation and strong vertical shear should set the stage for a pretty significant tornado outbreak. Storm motion appears to be a bit more manageable as well coming in around 40kts. Will be anxious to see how things look in the morning once the RUC takes over.
 
Based on a loop of infrared sat., it doesnt look like clearing is going to be an issue. Fair conditions are already pushing into MO from the west. 09Z RUC has 60° dews stretching into extreme SE IA and western IL at 21Z. I am leaving for Mcomb, IL and will readjust as needed. Have fun everyone.

Doug Raflik
920-210-3771
 
My model guidence is showing SEMO area along I-55 corridor being best spot to set up. DP's in Poplar bluff area already in mid 60's. Very high EHI values may be a bit influenced by CAPE # but we have had alot of good days with these #'s. Probably we will set up around Poplar bluff to Sikeston MO. Good luck to chasers & stay safe.
 
Chase target:
Ottumwa, IA

Timing:
Storm initiation 3 PM CDT.

Comments:
Supercell storms with hail to 1.5â€￾ and isolated tornadoes.

Discussion:
Lead impulse within high-amplitude trough – the same one responsible for the severe WX in KS/OK/TX yesterday – has resulted in a round of widespread precipitation and storms in IA/IL/WI, which is currently exiting the area to the east. At 14Z, a SFC WF extended from eastward from low pressure near HJH along a LWD/IRK/STL line in MO. To the south of this boundary a moist and increasingly unstable airmass is in place, and this front will surge northward during the afternoon, reaching a DSM to BRL line by 18Z. Warm sector MLCAPEs will easily exceed 2000J/kG in areas where anticipated partial clearing takes place. Additionally, locally impressive hodograph curves will be in place near this boundary with a SSWRLY 40kt LLJ on top of backed 10kt SERLY SFC flow. This should support an environment conducive to rotating updrafts, as cloud bases will be in the 400m AGL range.

- bill
 
Leaving Mt. Vernon, IL, and heading slightly westward, and a north. Looking good here now..the sun is out, and the temps and dewpoints are starting to rise. Setting up between Litchfield and Jerseyville, IL. Latest models looking GREAT...even the weather channel has their own "greatest risk" special area now. Good luck all, and Ken H...keep the updates coming for me!! thanks!
 
While I agree that there is a big severe weather threat today in MO, I don't see enough directional shear to warrant the long-lived, strong tornado expectation you mentioned. Sure there is some speed shear but directional shear does not appear 'that' great based on wind profilers in the area. In fact, the is some backing of the wind at mid-levels. This setup looks more likely to be a solid line of raidly moving storms with Bow Echoes, wind damage and hail the main threat. The tornado threat is there, but the setup does not scream tornadic supercells IMO.
 
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