MESO: Mesoscale Discussion 0643

ACUS11 KWNS 152000
SWOMCD
SPC MCD 151959
OKZ000-TXZ000-152130-

MESOSCALE DISCUSSION 0643
NWS STORM PREDICTION CENTER NORMAN OK
0259 PM CDT WED MAY 15 2013

AREAS AFFECTED...MUCH OF NWRN TX

CONCERNING...SEVERE POTENTIAL...WATCH LIKELY

VALID 151959Z - 152130Z

PROBABILITY OF WATCH ISSUANCE...80 PERCENT

SUMMARY...ADDITIONAL STORMS EXPECTED TO FORM OVER NWRN TX...AND
POSSIBLY EXTENDING SWD ALONG THE DRYLINE LATER THIS AFTERNOON. VERY
LARGE HAIL IS LIKELY...WITH A DAMAGING WIND THREAT POSSIBLY
MATERIALIZING LATE AFTERNOON/EVENING ACROSS N CNTRL TX.

DISCUSSION...STORMS HAVE INCREASED IN INTENSITY AND COVERAGE JUST
AHEAD OF THE UPPER LOW FROM SRN OK INTO FAR NRN TX...WHERE A MOIST
AIR MASS EXISTS AND NO CAPPING. SOME OF THE INCREASE IN CORE
INTENSITY CAN BE ATTRIBUTED TO STEEPER MIDLEVEL LAPSE RATES AS WELL
AS AREAS OF HEATING UPSTREAM. THESE STORMS WILL CONTINUE TO HAVE A
MARGINAL HAIL THREAT...AS DEEP SHEAR PROFILES ARE MARGINAL FOR
SUPERCELLS WITH 25-30 KT.

VISIBLE IMAGERY SHOWS CU FIELDS INCREASING ACROSS NWRN TX...AND
EXTENDING SWD TO THE EDWARDS PLATEAU WHERE STRONG HEATING HAS
STEEPENED LAPSE RATES BENEATH COOL MIDLEVEL AIR. HIGH BASED
CONVECTION WAS NOTED OVER THE TX S PLAINS...INDICATIVE OF THE VERY
STEEP MIDLEVEL LAPSE RATES. AS THIS ACTIVITY CONTINUES E...IT WILL
INTERSECT THE STRONGER INSTABILITY AND MOISTURE. OTHER CELLS ARE
ALSO EXPECTED TO FORM OVER NWRN TX AS HEATING PERSISTS. NWLY FLOW
ALOFT ATOP SURFACE SELYS WILL PROVIDE AMPLE SHEAR FOR
SUPERCELLS...WHILE LARGE UPDRAFT ACCELERATION AIDS IN THE
DEVELOPMENT OF LARGE DAMAGING HAIL.

CONGEALING OUTFLOWS WITH TIME SHOULD CAUSE STORMS TO MERGE INTO ONE
OR MORE MCS/S...POSSIBLY FORWARD PROPAGATING INTO THE METROPLEX AREA
LATER TODAY WITH BOTH HAIL AND DAMAGING WINDS.

ANY STORMS THAT FORM FARTHER E NEAR THE I-35 CORRIDOR MAY HAVE A
BRIEF TORNADO THREAT...WHILE PROPENSITY FOR MERGING OUTFLOWS WITH
HIGHER BASED ACTIVITY TO THE W WILL FAVOR WIND AND HAIL.

..JEWELL/CARBIN.. 05/15/2013

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

ATTN...WFO...FWD...OUN...SJT...LUB...MAF...

LAT...LON 31100043 31160073 31450103 31940076 32580046 33200030
33870017 34339968 34399961 35039680 35049625 34819611
34569612 32769663 32439669 31839727 31529789 31100043

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