MESO: Mesoscale Discussion 1815

ACUS11 KWNS 311924
SWOMCD
SPC MCD 311924
INZ000-KYZ000-ILZ000-MOZ000-312130-

MESOSCALE DISCUSSION 1815
NWS STORM PREDICTION CENTER NORMAN OK
0224 PM CDT SAT AUG 31 2013

AREAS AFFECTED...CNTRL/SRN IL...W-CNTRL/SWRN IND

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 311924Z - 312130Z

PROBABILITY OF WATCH ISSUANCE...40 PERCENT

SUMMARY...TSTM INITIATION IS EXPECTED SOON ALONG A FRONTAL BOUNDARY
EXTENDING ACROSS CNTRL IL. A STRONGLY UNSTABLE ENVIRONMENT WILL
LIKELY PROMOTE A FEW SVR STORMS WITH STRONG WINDS/LARGE HAIL
POSSIBLE. AN UPGRADE TO SLIGHT RISK IS BEING PLANNED FOR 20Z AND
TRENDS ACROSS THE AREA ARE BEING MONITORED FOR A POSSIBLE WW.

DISCUSSION...RECENT VISIBLE SATELLITE IMAGERY HAS RECENTLY SHOWN
MORE AGITATED CU ALONG A FRONTAL BOUNDARY EXTENDING FROM 20 NNE PIA
/IN CNTRL IL/ SWWD TO SZL IN NW MO. TEMPERATURES AHEAD OF THIS
BOUNDARY ARE IN THE MID TO UPPER 90S AMIDST LOW TO MID 70S
DEWPOINTS. AS A RESULT...STRONG INSTABILITY /MLCAPE OVER 2500 J PER
KG PER RAP-BASED MESOANALYSIS/ EXISTS ACROSS THE AREA. MODIFIED 12Z
RAOBS AND RECENT MESOANALYSIS REVEAL LITTLE TO NO CINH REMAINS AND
TSTM INITIATION IS EXPECTED SOON.

ONCE THUNDERSTORM INITIATION OCCURS...THERE IS A POTENTIAL FOR QUICK
UPDRAFT GROWTH WITH THE POSSIBILITY OF BOTH LARGE HAIL AND DAMAGING
WINDS. SHEAR ACROSS THE AREA IS GENERALLY LOW WITH MESOANALYSIS
ESTIMATING EFFECTIVE SHEAR VALUES AROUND 25 KT. HOWEVER...RECENT WV
SATELLITE IMAGERY SHOWS A COMPACT DISTURBANCE MOVING THROUGH CNTRL
IA. AS THIS FEATURES MOVES INTO THE MID MS VALLEY...SOME INCREASE IN
VERTICAL SHEAR IS POSSIBLE...IN ADDITION TO ENHANCED LARGE-SCALE
LIFT.

THIS COMBINATION OF THESE FACTORS FAVORS AN INCREASED SVR RISK WITH
ANY TSTMS THAT DO DEVELOP ACROSS THE AREA. SOME POTENTIAL ALSO
EXISTS FOR COLD POOL CONGLOMERATION AND UPSCALE GROWTH...ALTHOUGH
UNCERTAINTY IS HIGH REGARDING THAT SCENARIO ATTM. AN UPGRADE TO
SLIGHT RISK IS BEING PLANNED FOR 20Z AND TRENDS ACROSS THE AREA ARE
BEING MONITORED FOR A POSSIBLE WW.

..MOSIER/GOSS.. 08/31/2013

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

ATTN...WFO...LMK...IND...PAH...LOT...ILX...LSX...

LAT...LON 39699078 40129009 40718937 40858869 40508751 40178693
39508633 38268673 37868806 37518866 37668948 37968992
38839063 39699078

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