[BNAWX] Severe Storm Outlook Narrative

[EMWIN Server]

ACUS11 KWNS 171703
SWOMCD
SPC MCD 171703
KYZ000-TNZ000-INZ000-171900-

MESOSCALE DISCUSSION 2170
NWS STORM PREDICTION CENTER NORMAN OK
1103 AM CST MON DEC 17 2012

AREAS AFFECTED...CNTRL/WRN KY...PARTS OF WRN/MIDDLE TN...FAR SRN IND

CONCERNING...SEVERE POTENTIAL...SEVERE THUNDERSTORM WATCH LIKELY

VALID 171703Z - 171900Z

PROBABILITY OF WATCH ISSUANCE...95 PERCENT

SUMMARY...SVR THUNDERSTORMS...INCLUDING SUPERCELLS...ARE EXPECTED TO
DEVELOP ACROSS PARTS OF THE LOWER OH AND TN VALLEY BETWEEN 18Z AND
20Z. SVR HAIL...POTENTIALLY TO GOLFBALL SIZE...ALONG WITH SVR WIND
GUSTS WILL BE POSSIBLE. A SEVERE THUNDERSTORM WATCH WILL LIKELY BE
ISSUED EARLY THIS AFTERNOON.

DISCUSSION...WATER VAPOR LOOPS REVEAL A MID-LEVEL DRY SLOT IN
ADVANCE OF A MID-LEVEL VORT MAX CURRENTLY ENTERING WRN MO. THE VORT
MAX WILL CONTINUE TO TRACK ENEWD IN TANDEM WITH A LEADING ASCENT
MAX -- EVIDENT OVER THE INTERSECTION OF THE OH AND MS RIVERS PER
WATER VAPOR IMAGERY. THIS DRY SLOT IS ALLOWING TEMPS TO CLIMB INTO
THE UPPER 50S TO LOWER 60S AMIDST A CORRIDOR OF PARTIAL SUNSHINE
SOUTH OF A STATIONARY FRONT THAT LIES APPROXIMATELY ALONG THE OHIO
RIVER. MODIFIED FORECAST SOUNDINGS SUGGEST THAT THESE TEMPS COMBINED
WITH ANOMALOUSLY HIGH DEWPOINTS IN THE 50S ARE CONTRIBUTING TO
MLCAPE VALUES OF 400-800 J/KG. STORMS WILL LIKELY DEVELOP BETWEEN
18Z AND 20Z ALONG AN EWD-MOVING CONFLUENCE AXIS CURRENTLY EXTENDING
FROM OWB TO SW OF HOP. DESPITE THE MARGINAL INSTABILITY...LARGE
NORMALIZED CAPE VALUES -- PARTLY OWING TO THE INFLUX OF 7-8 C/KM
MID-LEVEL LAPSE RATES -- WILL YIELD INTENSE UPDRAFT ACCELERATIONS
GIVEN 30-45 KT OF DEEP SHEAR. NEARLY UNIDIRECTIONAL WSWLY FLOW
THROUGH THE CAPE LAYER FEATURING LONG HODOGRAPHS WILL SUPPORT
SUPERCELL STRUCTURES AND QUASI-LINEAR SEGMENTS WITH HAIL POTENTIALLY
REACHING GOLFBALL SIZE...ALONG WITH STRONG TO MARGINALLY SVR WIND
GUSTS.

..COHEN/CORFIDI.. 12/17/2012

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

ATTN...WFO...JKL...ILN...LMK...OHX...PAH...MEG...

LAT...LON   37488407 35838562 35518708 35988824 36768833 37228813
            37788747 38178650 38728500 38848442 38628403 38248382
            37488407



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