Mesoscale Discussion 1621

Issued

Jul 27, 2012, 12:52 PM CDT (17:52 UTC)

Expired

Jul 27, 2012, 3:15 PM CDT

In force

2 hr

Issued by

the Storm Prediction Center

Chance of a watch

60%

The Evansville,IN radar (KVWX), 66 km from the middle of the area, began a volume at 17:53 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

• Severe Thunderstorm Watch 532Jul 27, 1:45 PM CDT

398 
ACUS11 KWNS 271752
SWOMCD
SPC MCD 271752 
OHZ000-INZ000-KYZ000-ILZ000-MOZ000-272015-

MESOSCALE DISCUSSION 1621
NWS STORM PREDICTION CENTER NORMAN OK
1252 PM CDT FRI JUL 27 2012

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

Mesoscale Discussions in Indiana, 2012Mesoscale Discussions in Illinois, 2012Mesoscale Discussions in Ohio, 2012Every mesoscale discussion in 2012

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.