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MESOSCALE DISCUSSION 0273
NWS STORM PREDICTION CENTER NORMAN OK
1058 PM CDT SUN MAR 17 2013
AREAS AFFECTED...SRN THROUGH CNTRL AND ERN AR INTO NWRN MS AND WRN
TN
CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE
VALID 180358Z - 180630Z
PROBABILITY OF WATCH ISSUANCE...40 PERCENT
SUMMARY...STORMS ARE EXPECTED TO UNDERGO A GRADUAL INCREASE IN
COVERAGE AND INTENSITY FROM SRN THROUGH CNTRL AND ERN AR INTO NWRN
MS AND WRN TN NEXT SEVERAL HOURS. ISOLATED LARGE HAIL AND DAMAGING
WIND WILL BE THE MAIN THREATS...THOUGH A TORNADO OR TWO CANNOT BE
RULED OUT FROM SRN AR INTO NWRN MS AND SWRN TN. WW IS POSSIBLE...BUT
ISSUANCE WILL ULTIMATELY DEPEND ON CONVECTIVE TRENDS.
DISCUSSION...LATE THIS EVENING A QUASI-STATIONARY FRONT EXTENDS FROM
THE TN VALLEY SWWD THROUGH WRN TN...ERN AND SRN AR INTO NERN TX.
DEWPOINTS NEAR 60 HAVE ADVECTED THROUGH THE WARM SECTOR BENEATH A
WARM EML RESULTING IN 500-1000 J/KG SBCAPE ALONG AND SOUTH OF THE
BOUNDARY. AN AXIS OF HIGHER THETA-E AIR WITH UPPER 50S DEWPOINTS
HAVE ALSO ADVECTED ABOVE THE STABLE SURFACE LAYER NORTH OF THE FRONT
RESULTING IN 1000-1500 J/KG MUCAPE AS INDICATED ON THE 00Z RAOB FROM
LITTLE ROCK AR.
A STOUT INVERSION ASSOCIATED WITH ERN EXTENSION OF THE EML HAS SO
FAR INHIBITED DEVELOPMENT OF DEEP CONVECTION...BUT WV IMAGERY SHOWS
A SHORTWAVE TROUGH MOVING THROUGH OK AND NRN TX. AS LEADING EDGE OF
MID LEVEL ASCENT ACCOMPANYING THIS FEATURE BEGINS TO OVERTAKE
INSTABILITY AXIS...THE INVERSION SHOULD WEAKEN AND PROMOTING AN
INCREASE IN STORMS NEAR AND NORTH OF THE QUASISTATIONARY FRONT
TONIGHT. TRENDS IN RADAR IMAGERY AND LIGHTNING DATA INDICATE
CONVECTION IS ALREADY BEGINNING TO DEEPEN AND SLOWLY INTENSIFY OVER
SERN AR/NWRN MS. STRONG EFFECTIVE SHEAR AND STEEP MID LEVEL LAPSE
RATES WILL SUPPORT POTENTIAL FOR UPDRAFT ROTATION AND A THREAT OF
LARGE HAIL. SOME OF THE STORMS DEVELOPING NEAR THE FRONT MAY ALSO
POSE A THREAT FOR ISOLATED DAMAGING WIND. LARGE HODOGRAPHS EXIST IN
VICINITY OF FRONT FROM ERN AR INTO NWRN MS AND WRN TN...SUGGESTING A
THREAT FOR A COUPLE OF TORNADOES. HOWEVER...A NEAR SFC BASED
INVERSION LIKELY EXISTS IN THIS AREA BASED ON CURRENT WARM SECTOR
TEMPERATURES AND DEWPOINTS...INDICATING ACTIVITY IS PROBABLY
SLIGHTLY ELEVATED.
..DIAL/THOMPSON.. 03/18/2013
ATTN...WFO...MEG...JAN...LZK...SHV...
LAT...LON 36048922 34838940 33219233 33159390 33809373 35719124
36048922
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