MESO: Mesoscale Discussion 1763

ACUS11 KWNS 160211
SWOMCD
SPC MCD 160211
OHZ000-INZ000-ILZ000-160315-

MESOSCALE DISCUSSION 1763
NWS STORM PREDICTION CENTER NORMAN OK
0911 PM CDT WED AUG 15 2007

AREAS AFFECTED...XTRM NERN IL...NRN IND AND NWRN OH

CONCERNING...SEVERE POTENTIAL...WATCH LIKELY

VALID 160211Z - 160315Z

TSTMS THAT DEVELOPED IN THE CHICAGOLAND AREA HAVE SHOWN A RECENT
INCREASE IN INTENSITY OVER NWRN IND WHERE HAILSTONES TO THE SIZE OF
NICKELS HAVE BEEN REPORTED. ACTIVITY APPEARS TO BE DEVELOPING ALONG
THE BACKSIDE OF A DEPARTING SPEED MAX/MCV WHERE WARM ADVECTION IS
BEING MAXIMIZED OVER A WEAK COLD POOL AND AHEAD OF A LOW-AMPLITUDE
PERTURBATION UPSTREAM OVER THE CORN BELT.

ACTIVITY HAS PROBABLY BEEN SLIGHTLY ELEVATED...BUT TAIL-END TSTM
APPEARS TO BE TRENDING MORE SFC-BASED. LATEST MESOANALYSIS SHOWS A
WEAK BOUNDARY...LIKELY A FOOTPRINT OF EARLIER DAY TSTMS...EXTENDING
FROM SW OF KFWA NWWD TO THE TAIL-END STORM. THOUGH THERE IS A WEAK
WIND SHIFT PRESENT...AIR MASS EITHER SIDE OF THE BOUNDARY WAS
SUFFICIENTLY UNSTABLE TO SUPPORT STG TSTMS.

IWX VWP EXHIBITS NEARLY 50 KTS OF EFFECTIVE SHEAR...SUPPORTIVE OF
EMBEDDED ORGANIZED STORMS. OTHERWISE...GIVEN GEOMETRY OF THE
LOW-LEVEL JET WITH RESPECT TO THE DEVELOPING TSTM CLUSTER AND
PRESENCE OF AMPLE INSTABILITY DOWNSTREAM...SITUATION WILL LIKELY
YIELD SPORADIC DOWNBURST/DMGG WINDS ALONG WITH HAIL. ATTM...IT
APPEARS THE GREATEST SVR THREAT WILL EVOLVE ESEWD FROM PORTER AND
LAKE COUNTIES ESEWD BETWEEN KGUS-KFWA. ACTIVITY COULD ALSO EVOLVE
INTO A HEAVY RAINFALL THREAT SEWD ACROSS NRN IND INTO NWRN OH IN A
FEW HOURS.

A SEVERE THUNDERSTORM WATCH WILL BE ISSUED SHORTLY.

.RACY.. 08/16/2007

..PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...CLE...ILN...IWX...IND...LOT...

40748672 41228804 41478850 41778850 41718747 41628651
41308377 40558359 40128396 40288526

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