4/14/2006 FCST: IL, IN

John Farley

Supporter
Surprised nobody has started a thread for 4/14. 0Z NAM shows cape 2500-3500 and helicity 200-300 over central and eastern IL roughly along I-72 from Springfield to Urbana/Champaign. It also develops precip in this area between 18Z and 0Z. I would imagine that the specific location where storms fire could be influenced by tonight's convection, but it would seem to me that there will be decent potential somewhere in IL and/or IN.
 
I have my eye on today also. Plenty of cape, LCL levels should be low, boundaries from last night and ongoing convection moving through should influence development. I imagine that the focus of activity will be further east than the SPC is showing presently.

I am working till noon so have little time for further analysis. My quick look at the situation shows some potential.

The lack of discussion is largely due to the location of the chasers. The great plains folks ignore slight risks east of IL. There is a pocket of chasers in MI who cover the north of Indiana. One frequent poster from WV also. In general though you will find that the Ohio valley gets less scrutiny than the plains.

--
Tom Hanlon
 
As of 12:36 pm West Central Indiana is overcast due to ongoing storms in centrail Illinois. Daytime heating and/or instability is now more favored in south east illinois, and southern indiana for mid/late afternoon storm development. Chase target is for 30-60 miles west of Terrahaute, Indiana into Illinois countryside.

Good luck to those chasing in Illinois/Indiana
 
Would someone explain this sentance from the SPC Day 1 outlook...

ANY TORNADO THREAT SHOULD REMAIN GREATER NEAR THE SURFACE BOUNDARY WHERE RICHER BOUNDARY LAYER MOISTURE AND STRONG LOW LEVEL SHEAR WILL RESIDE.

specifically what is the "surface boundary" they are talking about and how do I identify it. I know the generic definition but I don't understand how to convert the above into something useful.
 
Catch the early half of that paragraph:

OUTFLOW FROM LAST NIGHTS MCS APPEARS TO ARC FROM
ERN KY NWWD INTO CENTRAL/SRN IL THIS MORNING. ONGOING STRONG/SEVERE
THUNDERSTORM CLUSTER OVER CENTRAL IL IS NOW ROOTED ABOVE STRONG
CAPPING AND WILL MOVE QUICKLY ESEWD AND THEN MORE SEWD JUST NORTH OF
THIS BOUNDARY THROUGH THE AFTERNOON.

The outflow boundary / wind shift line from the current storm system.
 
There has been a persistent area of very high storm-relative helicity values over the upper Ohio valley showing up on the SPC's mesoanalysis page, contributing to STPs af 3, EHIs of 3-5 and supercell composites peaking at 20 in this area.

Now I fully understand the pitfalls of using the mesoanalysis page, but could this be remotely correct? My first thought was a bad data point, but it's been like that now for a few hours and is certainly commanding attention.
 
Dan, I've been noticing this build in parameters through upper OH valley also. A check of some parameters indicated by the RUC over the next 3-6 hours, characterized by very steep lapse rates (>10 @ 0-1.5km). Instability continues to build, but looks like some signs of CIN erosion roughly from W to E. Looks like some cirrus cover, but w/ a decent break over SE OH now. One concern is prospect for any backing of surface winds, although some hint of a wave in SLP to be moving through. Will be interesting to keep an eye on E OH, W PA and N WVA as heating progresses today.
 
Looks like some cirrus cover, but w/ a decent break over SE OH now. One concern is prospect for any backing of surface winds, although some hint of a wave in SLP to be moving through. Will be interesting to keep an eye on E OH, W PA and N WVA as heating progresses today.
[/b]

Just getting to some data here at 5:30. Looks like the cirrus cover has expanded. Storms moving east from Western Ohio at a fast pace. I suspect that storm might go through some strengthening as it heads east.

Curious to see if it picks up any rotation.

--
Tom Hanlon
 
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