10/18/07 FCST: WI/MI/IA/MO/IL/IN/OH/KY/TN

[Travis Carlson]

Setup just keeps looking better and I can't wait to see more model runs. I like how the system is slowing down and timing is becoming increasingly better. If that continues that MDT risk will be scaled back more to the west putting areas along and just east of the Mississippi River in Illinois at risk too. I'm concern about heating and morning convection as well but what I do like is the dry slot should help to get some of the cloud debris and convection out of here I'm hoping allowing breaks in the clouds and redevelopment to occur. A very good setup closely related to Thurs. setup is April 19, 1996! That was an incredible day if everyone remembers that one. Only thing really lacking on this setup is that I would like to see more directional shear and the time of year to be April instead of October, but you can't always get what you want. I like two areas however, near Champaign Urbana in Central Illinois or farther to the north in Northern Illinois where you'll be closer to the warm front with better directional shear. Regardless, pack up the equipment because it's looks like a major severe weather outbreak on tap.

 

[Terry Tyler]

its been too long without decent storms...looks like well atleast see a wicked squall line down here in north, MS...the SPC even talked a bout extending the MDT risk area into the gulf coast states...

that would be really nice...

i cant wait!

 

[Mark Sefried]

Like others I am also closely watching the upcoming system for Thursday. Each model run seems to slow the system down and this makes sense of course which such a strong low being forecasted. NAM looks very good as of now with great directional shear (more negatively tilted low) while the GFS is not as favorable and is showing more unidirectional windfields. If the NAM is correct (granted it is still two days out) it should be very intresting with the possiblity of tornadoes (some possibly strong and long tracked) across the Eastern Midwest. It is definantly worth keeping an eye on for sure. Thankfully I was able to get the go ahead from my boss at work to get the day off if I need it.

 

[Dan Cook]

http://www.usawx.com/eta_500_wind_4818znam1a.gif

http://www.usawx.com/eta_500_wind_5118znams.gif

Those are some insane winds..

 

[sebenste]

10/18/07: Illinois

Wednesday will be an interesting day in OKC-land. But 24 hours later, the fun rapidly shifts northeastward as the low starts to occlude over southeastern MN by Thursday evening.

If you look at the surface data, the NAM tonight has not done very well with
the initialization of the surface moisture field. But for us in Illinois,
this will be no problem. A strong low level jet in advance of the system, 60
knots plus, from 0Z Thursday onward will draw that moisture rapidly
northward, producing copious rainfall across our area Wednesday night in the
isentropic lift zone. Between that and advected moisture, lower 60 plus
dewpoints are a lock over northern Illinois by Thursday noon, as well as
surface temps near or at 80 degrees and almost due south sustained surface
winds at 20 knots plus.

By mid-late afternoon, the mid-level dry slot will be moving into northern
Illinois. It seems as though any isentropic lift will be out of the area
fairly early, so we could have at least a few hours of decent sunshine here
before convective temps are reached. Temps around 80 with mid-60 dews should
result in mean CAPE of 1,500 J/KG and possibly higher, much of it coming in
the low levels, so SBCAPE will be decent as well; NAM says 1,400-ish, which
is believable. 0-6 KM shear of 80 knots and 0-1 KM shear of 30 knots, EHI of
10-15 across north central and northeast IL...not bad. Low level shear isn't
bad ahead of the cold front in northern Illinois; SRH is around 250 J/KG;
convective temp is 72 and is reached by 18Z, so like the situation we'll see
on Wednesday, this is going to be an early show, with severe thunderstorms
blowing up around noon (heck, it could be over with by 20Z at my spot 60 miles west of Chicago if the
timing holds up).

40 knot or greater storm speed means things will be moving fast. As of right
now, it appears the best shear/instability combo may be over northeast Illinois, southeast of the triple point. Metro Chicago/Rockford/LaSalle
better watch out Thursday from noon on...this should be several supercells
transitioning quickly into a squall line with a few imbedded supercells with
nasty surprises. I have to be at NIU for this one, but if one threatens us,
I can and I will go after it.

 

[John Farley]

I'm less bullish on this system, for my area (southern IL), anyway, than I was earlier. Now if I were in the Chicago area, or even maybe west Michigan, I would be excited - I agree with Gilbert on the potential for the Chicago area. The parameters also look pretty good for west Michigan, but in that case, a lot will depend on the ability of the storms to hold together as they move across Lake Michigan. For southern IL, though, it looks like the system timing will be too fast - if this evening's model runs are correct, it will be past southern and much of central IL before daytime convection gets going - through around and north of the Peoria area there is some potential, depending on when initiation occurs. The best combination of directional shear and instability seems to be roughly along a line from Peoria to Chicago to Grand Rapids, and the models kick out a fair amount of precip there (especially from Chicago into W. Michigan and maybe SE Wisconsin), too - though the GFS seems to have this a little northwest of the WRF.

There is some potential farther south along the IL/IN border and eastward, but less instability and more unidirectional (though perhaps stronger) wind shear would seem to make this area much more marginal - and the models also show very little precipitation in this area. Combine this with the 40 knot movement of the storms, and I am not too optimistic. Seems pointless from the southwest to try to keep up with the storms as they race into the Chicago area, though if I were already there I would be pretty keyed. And the setup farther south looks a little too marginal right now for me to go after it. Still, it is still a day and a half out, and quite a bit could change from tonight's model runs, so I will watch and see how it looks as the event gets closer. I'm still open to chasing if things look better for the southern IL area, but right now I am not too hopeful.

 

[Dan Robinson]

I'm with John on this - the 00z GFS and NAM clear out everything through southern IL/IN by 18Z! Huge squall line across MO and through STL early in the morning, then that's it. Timing could change, but I'm not as optimistic for what were my preferred options along I-64 and I-70. N IL is too far of a drive for a highly conditional setup. Setups like these you almost have to just wait for the morning of to make any decisions. Friday in KY/OH/WV almost looks like a better bet for anyone east of I-75.

 

[Andrew Pritchard]

If I was coming from far off, I probably would be a little less concerned with tomorrow, but since it looks like the target area will likely be my driveway I'm keeping an eye on it. The speed shear is clearly not a problem, however directional could be better. Southerly surface winds aren't the end of the world though, and will still give us a little bit of turning with height.

It looks like we'll get a significant dry punch through central and eastern Illinois during the afternoon, and I'll likely just be targeting the nose of that. It looks like we should see substantial destabilization during the early part of the day so I'm banking on severe thunderstorm development in that area. Mode will be the problem. It's Illinois in October with a high dynamic system with less than ideal low level shear, so the odds are stacked against us getting much, if any discrete activity. However, being so local, I'll be out hoping for a window of discrete activity or a tail end storm.

If I had to pick an area that was most likely to see a few tornado reports (which I think if they occur, could be strong) is going to be along a line from Champaign to Kankakee, and areas a bit east and west of that into northern Indiana.

 

[David Draun]

Wow, even KLOT has decided not to downplay this one. They've posted a special statement on all zone forecasts.

I still don't like how the NAM shows much of the good parameters here early and gone quickly. I would love to see this system slow down just a little more so I can get out and chase by 2-2:30PM tomorrow. An ideal situation would be the repeated development like what is going to happen in the Southern Plains today.

 

[Brandon Sullivan]

Currently targeting the Joliet area.. I want to get out ahead of the front, and wait. Once activity fires, Joliet has a nice road network in any direction.. Daytime heating will play key to this. Proably will be leaving around 7 or so.. Good luck all. Still wish it would slow down a little bit.... Well see..

 

[Jesse Risley]

I'm out due to P/T conferences..but here is what I can see..

Good dynamics as already pointed out, but I'm expecting this to be a mainly linear forced event. I don't expect many discrete supercells; the main line will likely move rather quickly ENE. The key for storm positioning will be when and where storms fire after noon..which I'm banking will be somewhere between the IL river and I-55. The dry slot should move into that region by 10:00 A.M.

Shear values around 60 Kts and CAPE of 1400 J/KG does look good for an October setup. I like the Streator-Pontiac-Dwight region as an initial target, which would allow repositioning from there if needed. The Chicago region looks to have a nice road network on paper, but the traffic can be nightmarish at best.

 

[Joel Wright]

I think the hotspot for tomorrow will be in Indiana. Particularly the northern half of the state. Winds at 500mb will be a bit slower, which should allow for the updrafts to maintain themselves easier, and not get pushed over. Wind shear is still excellent in this area as well. Upper winds aren't quite as backed in this region either. I also think there'll be better moisture and sunshine in this area.

In much of Illinois/eastern IA into Wisconsin, the storms will be lower topped, have less available instability, and I think have more a tendency towards a rapid transition to linear mode. (Which of course may still distribute damaging wind gusts). Chasing in this area would be difficult as well, since the convection will fire here pretty early, and playing catch up as they zoom by at 50+mph might not be so pleasurable.

Unfortunately I have work obligations tomorrow, but if I were to chase (or call in sick ), I'd target Lafayette Indiana as a starting point. Storms in this area should pass through at the ideal time of day, and for the above reasons I think this would be a great starting point...

Good luck to everyone tomorrow!

 

[Jim Zandonai]

I agree with the N. IN and further south as a target. The front is going to already be by the MS river in the early AM so by Noon the front is already past RFD. Figures as I am off work at 1pm. With storms booking that fast chasing isnt likely.
So looks like the main severe threat will be east of here but I am not too worried about the cells or lines being too Severe so early in the A.M here..esp this late in the year with dewpoints in the mid 50s. Still quite impressive for Mid OCT up here !

 

[Adam Lucio]

I think Im going to start off near Morris. Good road network allowing me to shoot in almost any direction when the time calls.

NAM has this thing at 975mb?! Very impressive. Shear profiles look similar around the region with slightly more backing near the low, I would target closer to the Low in Northern IL if it can slow down some, although this doesn't appear to be the case. I don't like it being progged to cross the area around noon-1pm

Strong Unidirectional shear should aid in a very intense squall line. If any discrete activity can form ahead of this, I would put Northern IN at greatest risk, another reason Ive chosen Morris, I-80 will take me right there, I've driven it many times this year and have had very little traffic issues.

Tip to all chasing the area....avoid the I65/I90 interchange...very ugly with that construction.

Thats the plan as of now, live conditions will definitely be the decision maker tomorrow, the key for any discrete activity is going to be to find the largest clearing and work with that, if all else fails Ill settle with a decent shelf this time of year.

Good luck to everyone tomorrow.

 

[David Draun]

Per the RUC:
Some pretty nasty helicity values setting up in northern IL by 12Z. SBCAPE of about 1000J/kg moving in from the west. The wind crossover is looking just wicked. If only the area could bake under the near 80 degree temps prior to the afternoon FROPA, there would be a supercellfest in northern IL for sure. I think the threat for tomorrow is gonna begin realy early, probably dawn.