04/22/05: FCST: Midwest into the Southeast

18Z NAM shows a deep (999mb) ULL sitting over E IL/W IN. Storms should be ongoing across this area in the early morning hours, But by late morning we should see the sunshine peak out, Allowing for us to destabalize. SBCAPE values are currently progged at 2500 J/KG with LI's of -7 in most of C/S IN. This area will have VERY strong low-level shear with 200-300 0-3km SRH. Supercells should be the main convective mode, With all of them capable of producing VERY large hail, Damaging Winds and Isolated Tornadoes.

I'm inpressed with tomorrow, And I'd really like to chase even if I am this CLOSE to my main vacation, But the main action is barely a couple hundred miles S of Me....

WITH BOTH SPEED AND DIRECTIONAL SHEER SUPERCELLS ARE A HIGH PROBABILITY. WILL CONTINUE TO HIGHLIGHT THREAT IN HWO.

Latest Outlook
http://midwestchase.com/wxforecasts/04_22_05-1.gif

..Nick..
 
Just a heads up; you might want to alter the subject heading of this thread, as the SPC seems to think tomorrow's event will not be contained to the upper midwest; parts of MS, AL, TN, KY, GA, AR, LA, NC, and VA are all included in the MDT risk.

"...AND A SUBSTANTIAL SEVERE WEATHER OUTBREAK APPEARS POSSIBLE FRIDAY ACROSS MUCH OF THE MID SOUTH AND SOUTHEAST STATES..."
 
I am a little skeptical about the northern extent of the Moderate risk. I fear that the risk will be repositioned south in the next day one.

I suspect that ongoing convection will limit heating and therefore lessen our chances of severe.

Awful close to me here in OH so I may head to Cincinatti in the AM and take a look for myself.

Reasons for skepticism for the north would include a less than enthusiastic agreement on the moderate risk from the spc in the HWO and AFD for ILN and Indianapolis and Jackson KY.

Too far south into KY and I am unsure of the chaseabilty ? Any advice on that?

--
tom hanlon
 
It really depends on which model you go with. The NAM run makes it look decent, pulling td's of 75/65 into Illinois and Indiana...while the RUC and GFS have the low out of the area by early morning leaving us with dreary, windy and cold conditions. I'll be interested to see which run the SPC goes with. Due to the uncertainty, I wouldnt be surprised to see the moderate risk pulled off. There's a chance we could get a quick dry spot, and maybe some partial clearing, which could be all it takes...but we'll just have to see.

I'm not putting any faith in either run...and will just wait til tomorrow. Since the event is unfolding right over my house...I wont have to make a decision until it unfolds, luckily.
 
Winds are looking a bit too veered and it's looking too unidirectional in the northern extend of the MDT, Which of course was my main focus area.

We've both decided not to chase, For pretty much the same reasons, The setup ain't exactly perfect for tornadoes and We're leaving in less than a week for the Plains.

I'm not totally saying tomorrow is not going to be good for IN/OH, But well south of the area (non-chase terrain in the Gulf) is gonna have the better shot for tornadoes/significant severe weather....

..Nick..
 
Concerning IN/OH/KY (northern extent of the SPC's MDT...)

After looking very closely at the latest 12Z models, I am kind of convinced that me staying home today was a good decision. The latest 12Z NAM shows T in the upper 60's/lower 70's, with Td's around 55-60F, which looks rather reasonable given the current conditions. This yields SBCAPE values of around 2000J/KG for S IN/OH and KY, and 3500J/KG+ further south into TN/MS/AL. Low-level shear appears not be very supportive of tornadoes in the northern extent of the risk... But I can't rule them out totally, and LCL's are pretty low at ~800, so maybe a tornado or two could be possible soon after convection fires ahead of the SFC low in SE IL/SW IN in the next couple of hours. Latest satellite imagery shows clouds starting to clear out of the region, with temps beggining to rise, with a 66/61 T/Td at Vincennes, IN. Any isolated storm will be pretty much surface based, so I'm NOT ruleing out tornadoes in the IL/IN/OH/KY area... But it's gonna be more of a damaging wind event... And this stuff is gonna fire in a rather non-chaseable terrain, so I'm glad I stayed home for this event, as my chase vacation starts in five days...

..Nick..
 
As for the northern section of the SPC moderate risk, the only area I have the time to concern myself with. I feel like we are lacking a large enough clear/dry slot to get adequate heating before the event really kicks off. I am heading to Cincinatti regardless because it is so close. General skepticism as the hoped for clearing that would give us the needed heating seems to not be happening.

Visible satellite offers some hope, just wish we had more daylight. Might be too little to late for the northern section of the SPC MOD risk area.

I figured the SPC would have further limited the size of the MOD risk area in the latest update.


--
tom hanlon
 
Im remaining optomistic. That may bite me later...but, I'm growing desperate.

There is a really nice clearing taking place over central Illinois into Indiana right now allowing for some solar heating to take place. A Cu field is also forming in this area. I do still feel that storms will likely form in this clear slot, right near the Low across central IL early this afternoon, and head towards Indiana in the late afternoon. However, with the pre-frontal wind shift already into Indiana, I'm not sure how likely supercells will be. I dont know, this is all probably wishful thinking...but we'll see how things unfold. SPC did put out an MCD for central IL/central IN and said they would issue a WW shortly...but at the same time, removed the slight and moderate risks.

Either way...my final thoughts. I do think we will begin to see thunderstorms develop over eastern/southeastern IL into western IN around 3-4PM. Some could be supercellular but we'll probably see mostly a wind event.
 
Sitting here in 'non-chase terrain' with 66 temp and 64 dewpoint, watching the sun just now beginning to break through the canopy left from this morning's convection...with better defined clear slot a few hours away in Mississippi.

Right now, to this inexpert forecaster, it looks like respectable cape but unimpressive shear.

Could be interesting, though---I've already battened down everything in expectation of straight-line winds, but am loading the cams in hopes of front-door supes here in north Alabama.

Dave Gallaher
Huntsville, AL
 
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