ZCZC SPCSWOMCD ALL
ACUS11 KWNS 181807 
SPC MCD 181807 
OKZ000-TXZ000-181900-

MESOSCALE DISCUSSION 0688
NWS STORM PREDICTION CENTER NORMAN OK
0107 PM CDT MON MAY 18 2015

AREAS AFFECTED...PARTS OF SRN OK AND NORTH TX

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 

VALID 181807Z - 181900Z

PROBABILITY OF WATCH ISSUANCE...5 PERCENT

SUMMARY...AN ISOLATED THREAT FOR LARGE HAIL AND LOCALIZED DMGG WIND
GUSTS MAY ACCOMPANY DEVELOPING THUNDERSTORMS ACROSS SRN OK. TSTM
COVERAGE SHOULD REMAIN SPARSE ENOUGH TO PRECLUDE WW ISSUANCE.

DISCUSSION...LATEST VISIBLE SATELLITE LOOP SHOWS TSTM INITIATION
ALONG A WEAK WIND SHIFT DRIFTING SWD INTO SRN OK. A MOISTURE-RICH
AND WARM BOUNDARY LAYER IS YIELDING MLCAPE VALUES APPROACHING 2000
J/KG... DESPITE A SOMEWHAT MARGINAL MIDLEVEL LAPSE RATE PROFILE
/SAMPLED AT 6-6.5 C/KM IN 12Z OUN SOUNDING/. HOWEVER...SUFFICIENT
MIDLEVEL FLOW IS PRESENT TO YIELD EFFECTIVE SHEAR VALUES AROUND 30
KT...BUT WEAK FLOW IN THE LOWEST 3 KM AGL LENDS SOME UNCERTAINTY HOW
LONG-LIVED/ORGANIZED ANY ACCOMPANYING SVR THREAT MAY BE. ADDITIONAL
LIMITING FACTORS INCLUDE LARGE-SCALE MIDLEVEL HEIGHT RISES THAT ARE
OCCURRING...ALONG WITH WEAK LOW-LEVEL CONVERGENCE...WHICH MAY LIMIT
THE LONGEVITY AND WIDESPREAD GENERATION OF NEW CONVECTION THIS
AFTERNOON. PRIMARY THREATS WILL BE LARGE HAIL AND LOCALIZED STRONG
TO SVR WIND GUSTS...AND A WW IS NOT CURRENTLY ANTICIPATED.

..ROGERS/MOSIER/THOMPSON.. 05/18/2015

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

ATTN...WFO...TSA...FWD...OUN...

LAT...LON   34529789 34939683 35199644 35039603 34379610 34189618
            33919653 33339836 33989897 34529789 

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