AREAS AFFECTED...PORTIONS INDIANA...WRN OH...SERN IL...NWRN
KY...SERN MO.
CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE
VALID 271752Z - 272015Z
PROBABILITY OF WATCH ISSUANCE...60 PERCENT
SUMMARY...POTENTIAL WILL INCREASE THROUGH MID-AFTERNOON FOR STG-SVR
TSTMS TO DEVELOP INVOF SFC COLD FRONT OUTLINED BELOW...OVER PORTIONS
INDIANA/IL...MOVING TOWARD LOWER OH VALLEY. ADDITIONAL CONVECTION
NOW OVER W-CENTRAL INDIANA MAY OFFER SVR THREAT AS WELL. IN BOTH
CASES...DAMAGING GUSTS AND ISOLATED HAIL ARE POSSIBLE. THESE
REGIMES ARE INITIALLY SEPARATE BUT ULTIMATELY MAY AFFECT SOME OF THE
SAME AREAS AT DIFFERENT TIMES.
DISCUSSION...AT 17Z...SFC MESOANALYSIS SHOWED LOW OVER SRN LM...WITH
COLD FRONT SWWD ACROSS CENTRAL IL TO CENTRAL MO. SFC THERMAL AXIS
WITH TEMPS 90S F WAS EVIDENT AHEAD OF FRONT NEAR CVG-IND-STL-UNO
LINE. MOISTURE WAS MAXIMIZED FARTHER S INVOF OH RIVER. ALTHOUGH
NOT STRONGLY CONVERGENCE...FRONT SHOULD CONTRIBUTE TO STG-SVR TSTM
DEVELOPMENT AS IT MOVES INTO PROGRESSIVELY HIGHER-THETAE BOUNDARY
LAYER WITH LITTLE TO NO CAPPING. 1500-2500 J/KG MLCAPE SHOULD
BECOME COMMON FROM SERN MO OVER IL/SRN INDIANA WARM SECTOR...AS STG
DIABATIC HEATING AND UPPER 60S TO LOW 70S SFC DEW POINTS OFFSET
MODEST LAPSE RATES ALOFT. EFFECTIVE SHEAR MAGNITUDES COMMONLY 30-40
KT SUGGEST GENERALLY MULTICELLULAR ORGANIZATION. POTENTIAL IS MORE
UNCERTAIN WITH SWWD EXTENT INTO OZARKS...GIVEN WEAKER NATURE OF BOTH
FRONTAL FORCING AND SUPPORT ALOFT. STILL...THICKENING CU AND OCNL
TCU ARE APPEARING ON VIS IMAGERY FROM SRN IL INTO SRN MO AHEAD OF
FRONT.
FARTHER E...VIS IMAGERY HAS SHOWN AREA OF ACCAS AND DEEPER BUT
INITIALLY ELEVATED CONVECTIVE TOWERS MOVING FROM IL EWD ACROSS
INDIANA DURING MID-LATE MORNING. THAT ACTIVITY NOW APPEARS TO BE
RECEIVING SOME SFC-BASED INFLOW...AS IT MOVES OVER INCREASINGLY
STRONGLY HEATED/MIXED BOUNDARY LAYER WITH NEGLIGIBLE CINH. SFC
ANALYSIS SHOWS POCKET OF RELATIVELY DRY AIR OVER ERN INDIANA...WITH
SFC DEW POINTS LOW-MID 60S F...RESULTING IN CURRENT
RELATIVE/REGIONAL MIN IN MLCAPE AT 300-700 J/KG OVER ERN INDIANA/WRN
OH REGION. PRIND CONVECTION OVER THIS REGION WILL OUTPACE SPATIAL
RATE OF SFC MOISTENING DUE TO ADVECTION...BUT STILL MAY PRODUCE
ISOLATED HAIL AND POTENTIALLY DAMAGING GUSTS AS IT MOVED OVER
WELL-MIXED SUBCLOUD LAYER.
..EDWARDS/CORFIDI.. 07/27/2012
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...CLE...ILN...LMK...IWX...IND...PAH...LOT...ILX...
MEG...LSX...SGF...
LAT...LON 37199194 38588864 39828765 40878735 41268378 40338324
39588382 38548613 37338830 36509006 37199194
