SPC MD 676

MD 0676 CONCERNING SEVERE POTENTIAL…WATCH LIKELY FOR SWRN KS…WRN OK…NW TX…FAR ERN OK/TX PANHANDLES


MESOSCALE DISCUSSION 0676
NWS STORM PREDICTION CENTER NORMAN OK
0219 PM CDT SAT MAY 18 2013

AREAS AFFECTED...SWRN KS...WRN OK...NW TX...FAR ERN OK/TX PANHANDLES

CONCERNING...SEVERE POTENTIAL...WATCH LIKELY

VALID 181919Z - 182015Z

PROBABILITY OF WATCH ISSUANCE...95 PERCENT

SUMMARY...SCATTERED TSTM INITIATION IS EXPECTED ON THE DRYLINE BY
21-22Z. VERY LARGE HAIL...ISOLATED TORNADOES...AND DAMAGING WIND
WILL BE POSSIBLE. WATCH ISSUANCE IS EXPECTED IN THE NEXT HOUR OR SO.

DISCUSSION...LATEST SFC ANALYSIS DEPICTS THE DRYLINE EXTENDING FROM
SWRN KS INTO THE FAR ERN OK/TX PANHANDLES AND NW TX. VIS IMAGERY
SHOWS CU INCREASING IN THE WELL-MIXED AIRMASS IN THE VICINITY OF THE
DRYLINE ACROSS SW KS INTO THE TX PANHANDLE. WHILE ONE EMBEDDED VORT
MAX IS MOVING NWD OUT OF THE AREA...ANOTHER EMBEDDED VORT MAX OVER
SERN CO/NERN NM SHOULD AID IN CONVECTIVE INITIATION LATER THIS
AFTERNOON.

THE 18Z DDC SOUNDING SHOWS VERY STEEP LAPSE RATES IN EXCESS OF 9.5
C/KM IN THE 750-500 MB LAYER...WHICH WILL SUPPORT VERY HIGH TO
EXTREME MLCAPE OF 3000-4000 J/KG IN AREAS AHEAD OF THE DRYLINE THIS
AFTERNOON AND EARLY EVENING. WHILE FLOW IS RELATIVELY
MODEST...INCREASING SWLY MIDLEVEL FLOW IS SUPPORTING EFFECTIVE SHEAR
OF 35-45 KTS AHEAD OF THE DRYLINE...WHICH WILL BE MORE THAN
SUFFICIENT FOR SUPERCELL DEVELOPMENT UPON STORM INITIATION.

DISCRETE SUPERCELL ACTIVITY IS EXPECTED WITHIN THE FIRST 2-3 HOURS
OF INITIATION...WITH VERY LARGE HAIL IN EXCESS OF BASEBALL SIZE THE
PRIMARY THREAT. LARGE T/TD SPREADS AND RELATIVELY WEAK LOW-LEVEL
SHEAR WILL LIMIT THE TORNADO THREAT INITIALLY...BUT A MARKED
INCREASE IN THE LOW-LEVEL JET WILL INCREASE THE TORNADO THREAT
TOWARD EVENING ACROSS MAINLY NWRN OK INTO SWRN KS...WITH ISOLATED
STRONG TORNADOES POSSIBLE WITH ANY STORMS THAT CAN REMAIN DISCRETE
AFTER 00Z. HOWEVER...STORM CONSOLIDATION IN A WELL-MIXED ENVIRONMENT
MAY RESULT IN UPSCALE GROWTH AND A TRANSITION TO MORE OF A SEVERE
WIND THREAT THIS EVENING...POSSIBLY LIMITING THE WINDOW OF
OPPORTUNITY FOR A MORE ROBUST TORNADO THREAT.

..DEAN/KERR.. 05/18/2013

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

ATTN...WFO...ICT...FWD...OUN...DDC...SJT...GLD...LUB...AMA...

LAT...LON   37290112 37880150 38500134 38920033 38829937 38509866
            38129815 37669781 36889765 35559772 34699766 33459786
            32919805 32419816 32199830 31989879 31989936 32069993
            32170043 32790063 33780057 35300063 36140066 37290112

via SPC Forecast Products http://www.spc.noaa.gov/products/md/md0676.html