MESO: Mesoscale Discussion 0558

ACUS11 KWNS 261957
SWOMCD
SPC MCD 261956
OKZ000-TXZ000-262230-

MESOSCALE DISCUSSION 0558
NWS STORM PREDICTION CENTER NORMAN OK
0256 PM CDT FRI APR 26 2013

AREAS AFFECTED...WRN/CNTRL OK...FAR ERN TX PANHANDLE

CONCERNING...SEVERE POTENTIAL...WATCH LIKELY

VALID 261956Z - 262230Z

PROBABILITY OF WATCH ISSUANCE...80 PERCENT

SUMMARY...A FEW DISCRETE SUPERCELLS APPEAR LIKELY TO FORM BY 22-23Z
ALONG THE TX/OK BORDER AND DEVELOP SEWD INTO CNTRL OK THIS EVENING.
LARGE HAIL WILL BE THE PRIMARY HAZARD...BUT ISOLATED SEVERE WINDS
AND PERHAPS A TORNADO OR TWO WILL ALSO BE POSSIBLE.

DISCUSSION...19Z SURFACE ANALYSIS PLACED A 1011 MB CYCLONE IN THE
NRN TX PANHANDLE WITH AN ATTENDANT DRYLINE EXTENDING S/SWWD TOWARDS
THE PECOS VALLEY. A WARM FRONT THAT IS BECOMING QUASI-STATIONARY
EXTENDED E/SEWD INTO CNTRL OK TO THE ARKLATEX. CONVERGENCE ALONG
BOTH BOUNDARIES APPEARS TO BE STRENGTHENING IN RESPONSE TO THE
LOW-AMPLITUDE SHORTWAVE IMPULSE THAT WILL TRACK EWD ALONG THE KS/OK
BORDER...AS SURFACE PRESSURE FALLS HAVE INCREASED ACROSS SWRN
OK/NWRN TX. HERE...NEARLY FULL INSOLATION IS OCCURRING WITH SURFACE
TEMPERATURES WARMING THROUGH THE 70S INTO 80S AMIDST DEW POINTS
STILL RISING THROUGH 50S. THIS IS PROMOTING RAPID DESTABILIZATION
AND WILL YIELD WEAK TO EVENTUALLY MODERATE MIXED-LAYER BUOYANCY BY
EARLY EVENING.

12Z CONVECTION-ALLOWING WRF GUIDANCE ALONG WITH LATER MORNING HRRR
RUNS HAVE BEEN HIGHLY CONSISTENT WITH SIMULATING A BLOSSOMING OF
CONVECTIVE INTENSITY BY ABOUT 22Z. BASED ON CURRENT POSITION OF THE
SMALL CLUSTER OF TSTMS ATTENDANT TO THE SHORTWAVE IMPULSE...AND
INCREASING CU S ALONG THE DRYLINE...THIS SCENARIO APPEARS QUITE
REASONABLE. INITIAL DEVELOPMENT SHOULD BE RELATIVELY HIGH-BASED WITH
ELONGATED/NEARLY STRAIGHT-LINE HODOGRAPHS FAVORING SPLITTING
SUPERCELL STRUCTURES WITH MAIN THREATS OF LARGE HAIL AND ISOLATED
SEVERE WINDS.

..GRAMS/HART.. 04/26/2013

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

ATTN...WFO...TSA...OUN...AMA...

LAT...LON 36500012 36679938 36349830 35889738 35599653 34999689
34629796 34489882 34800001 35220033 36130046 36500012

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