5/30/08: FCST: KS/MO/IA/NE/MN/WI/IL/IN/OH/MI

[Bill Schintler]

Chase Target for Friday, May 30

Chase target:
Havana, IL (28 miles southwest of Peoria).

Timing and storm mode:
Storms should fire at 3 PM CDT, with a few supercells possible early in storm evolution. Transition to a large convective complex will take place by early evening.

Synopsis:
Flow over the Midwest will become increasingly zonal as the H5 streak travels towards the WRN Great Lakes through 00Z 05/31/08. Mid-level impulse now over ERN NEB will race E through IA and reach the Great Lakes by 18Z. A secondary S/WV will develop in its wake within the right-entrance region of a 100kt H3 speed max.

Discussion:
FCST challenge is the evolution of several convective complexes from tonight through Friday morning, with no obvious target standing out ATTM. Current thinking is that a large MCS will plow through much of NRN IL into WI well before the peak heating hours while robbing this area of instability. This will then limit SVR potential in the region that would otherwise be synoptically favored. The favored location may then be further SW along an OFB, where a 40kt WSWRLY LLJ should contribute towards significant hodograph curvatures despite strongly veered SFC flow. This area is also coincident with strong bulk shear with a 70kt WRLY mid-level jet, and instability with MLCAPEs to 2500J/kg despite mid-level lapse rates of only 6.5 C/km as SFC dewpoints rise into the low-70’s.

Feel free to PM me for nowcasting.



- bill
9:30 PM CDT, 05/29/08

 

[Adam Lucio]

If shear wasnt so largely unidirectional tomorrow I would be on my knees thanking the storm gods for a decent local setup for once, something that has been lacking in these parts.

That being said, I think Ill make my preliminary target somewhere along US-24 and I-55, perhaps El Paso. GFS puts the best CAPE further west, with SB values up to around 3500 j/kg...surely the best Ive seen around here so far this year...The best juice looks to be in the northern half of the state, perhaps aided by evaportranspiration.

Where I actually end up will depend highly on live conditions, Id like to see a boundary setup somewhere along the I-55 or I 74 corridors...if we can get a boundary that will provide the best chance for tornadoes early on. ANy sort of clearing will be a huge factor as well so tomorrow I plan just to see where things are coming together the best and going from there...I see very little capping and with the moderate instability in place I see things getting messy quickly, but after chasing for 5 days in the plains a local setup is more welcome.

The window for tornadoes appears narrow, hopefully this will change, if not I can be happy with a local shelf cloud and some severe wind/hail.

 

[Jesse Risley]

I'll agree with the rest of the pack that shear parameters certainly don't look great tomorrow. However, I don't see large amounts of sunlight necessary for a great outbreak tomorrow, given the other parameters that will already be in place. If we can get some sunlight to coincide with OFBs, then the potential for discrete, tornadic storms will exist before everything goes linear.

Given the crossover problems that the Illinois River poses chasing wise, I plan to target the Bloomington-PIA-SPI area and readjust as necessary once things start to fire in the afternoon. There is a good road network to intercept anything decent that trucks across the IL Rrver valley. The overnight MCS could certainly spoil an otherwise dynamic show, but as Adam stated it's the best setup potential we've had in these parts in some time, so I'll take what we can get.

Good luck to all tomorrow!

 

[Brandon Sullivan]

Hmm.. Lets jump in here too..

I am certainly keeping a close eye on the MCS gettin it on in IA headed this way.. I am going to wake up early and watch this mentioned line fall apart over central IL.

Lots of deep layer shear there, but nothing really from SFC-850.

Thus, any of these boundaries will play key into adding some more directional shear and larger hodographs...

Will probably head ESE maybe to PIA or Bloomington, or maybe SPI... Just like Jesse said..

Good luck all!

More in the morn.

 

[J West]

FCST challenge is the evolution of several convective complexes from tonight through Friday morning, with no obvious target standing out ATTM. Current thinking is that a large MCS will plow through much of NRN IL into WI well before the peak heating hours while robbing this area of instability. This will then limit SVR potential in the region that would otherwise be synoptically favored.

Based on the large area of general junky precip/storms ongoing over much of IA, S MN and SW WI, I think Bill's comments above are spot-on. The dynamics are there in Iowa as there are some cells rotating currently was they move east but by and large the crud will still in place early in the Day 1 period, severely limiting/completely quashing any hope at severe weather in the IL/WI border area. Currently MKE is at 53/34 and I also have a hard time seeing how the junk storms can get out of here early enough and the atmosphere can recover around a boundary quick enough. I would expect to see the northern extent of the MOD risk pulled back south to somewhere around the I-80 corridor...but SPC left that slight risk for all of southern WI on 5/29 even though there was no way anything severe was going to pop.

 

[Brent A. Clair]

Well, the MCS (that is, Mesoscale Crapfest System) moved a little further south than anticipated. This makes the afternoon's forecast just a little more difficult. First, where will the outflow boundary end up? I fear if it pushes too far south, then the atmos overhead is too stable, even for the fiercest storms. Second, will the clouds hang on throughout the morning into the afternoon? I think if we can get at least a few hours of sun, that will go a long way for destab. The fear is that the show will setup on a line SE of St. Louis to Decatur. I was wanting a little further west so to setup overhead, but the MCS is going to make things difficult.

On the bright side, everything else is prime: CAPE, CIN, decent helicity, Sigtor, Sigsvr; they all show nice large values. Just need the kicker to put it through the posts.
Will re-evaluate around 11 once these showers pass through and see what it did to the atmos. Good luck to those going out; I'm stuck in EOC duty again (large city graduation, outdoors tonight)
Later

 

[Chris Nuttall]

Sitting in Council Bluffs, IA, right now. Going to try to make a play in N Central MO as there appears to be a secondary surface low developing in E KS. I'm hoping the area is far enough removed from the MCS that there will be good instability.

Lack of shear worries me, but any remaining OFB and if that surface low develops, then we might be able to get backing surface winds.

Heading out in a few minutes for Kirksville, MO.

 

[Brandon Sullivan]

Currently en route to Bloomington, IL. The MCS appears to have slowed up pretty good west of the IL River. Do have some breaks in clouds over me right now, but it is hot and humid any ways..

I think as the OFB pushes east just a little more, it will stall somewhere near the IL river hopefully.. As the disturbance moves through later, things should re ignite along the boundary. I want to be close to that boundary for the enhanced shear...

Will be able to re-adjust from Bloomington if need be..

 

[Mike Johnston]

By satellite and radar, I think we can analyze an outflow boundary oriented from just south of St. Joseph, MO to Atchison to just west of Topeka, slowly sagging south.

Looks like relatively early convection could break out along the U.S. 71 corridor in west central MO, from Harrisonville to Butler to Nevada. Perhaps that boundary will be in the vicinity. As others have mentioned, speed shear in place, but lack of directional shear.

Concerned that the secondary surface low in Kansas will influence surface winds for only a few more hours, as the models show positively tilted trough and badly veering surface winds developing in the wake of the primary low heading towards the Great Lakes later this afternoon.

 

[Jared Farrer]

Currently sitting in Champaign, Adjustments will probably be made once I locate the position of the boundry? Brandon I may head your way here soon. You can call me if you want to you. 765 401 0665? No problem!

Anyway we will see how this thing unfolds?

 

[rdale]

17Z sounding from ILX combined with TAMDAR soundings showing a pretty healthy cap. Wake low brought some high winds into northern IL but looks like rest of that MCS has fallen apart.

 

[Scott Weberpal]

If the 15z RUC is any indicator, SE KS is the place to be. Vertical shear profiles yield more veering with height than in IL, along with 3500+ forecast CAPE...that's where we're heading. RUC has been consistent breaking out a tail-end monster along the KS/OK border by 00z, I hope it's right.