931  
ACUS11 KWNS 042334  
SWOMCD  
SPC MCD 042334  
ARZ000-OKZ000-050100-  
 
MESOSCALE DISCUSSION 1781  
NWS STORM PREDICTION CENTER NORMAN OK  
0534 PM CST MON DEC 04 2017  
 
AREAS AFFECTED...PORTIONS OF EASTERN OK AND WESTERN/CENTRAL AR  
 
CONCERNING...SEVERE THUNDERSTORM WATCH 519...  
 
VALID 042334Z - 050100Z  
 
THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 519  
CONTINUES.  
 
SUMMARY...AN ISOLATED THREAT FOR MAINLY STRONG TO DAMAGING WINDS  
SHOULD CONTINUE ACROSS WW 519 FOR THE NEXT SEVERAL HOURS. DOWNSTREAM  
WATCH ISSUANCE INTO MORE OF WESTERN/CENTRAL AR WILL PROBABLY NOT BE  
NEEDED.  
 
DISCUSSION...MOSAIC RADAR IMAGERY FROM 2330Z DEPICTS A BROKEN LINE  
OF THUNDERSTORMS EXTENDING ALONG AND JUST AHEAD OF A SURFACE COLD  
FRONT ACROSS EASTERN OK INTO FAR NORTHWESTERN AR. SEVERAL OTHER  
THUNDERSTORMS HAVE RECENTLY DEVELOPED ACROSS SOUTHWESTERN AR WITHIN  
THE OPEN WARM SECTOR. A FEW CELLS WITHIN THE BROKEN LINE HAVE  
EXHIBITED SUPERCELL CHARACTERISTICS OVER THE PAST SEVERAL HOURS,  
WITH SPORADIC LARGE HAIL AND STRONG/DAMAGING WINDS BEING REPORTED.  
THE AIRMASS IMMEDIATELY DOWNSTREAM OF THIS ONGOING CONVECTION SHOULD  
REMAIN FAVORABLE FOR MAINTENANCE OF SEVERE THUNDERSTORMS IN THE  
SHORT TERM, AS MLCAPE AROUND 500 J/KG AND EFFECTIVE BULK SHEAR  
VALUES OF 40-50 KT ARE PRESENT ACROSS WESTERN AR. A TORNADO CANNOT  
BE COMPLETELY RULED OUT GIVEN VEERING LOW-LEVEL WINDS SUPPORTING  
EFFECTIVE SRH AROUND 275-325 M2/S2. HOWEVER, THE PRIMARY SEVERE  
THREAT WILL LIKELY TRANSITION TO STRONG/DAMAGING WINDS AS THE  
SURFACE COLD FRONT OVERTAKES ONGOING CONVECTION, WITH THESE  
THUNDERSTORMS QUICKLY GROWING UPSCALE INTO A SOUTHEASTWARD-MOVING  
SQUALL LINE.  
 
WHILE SOME SEVERE THREAT MAY EXIST TO THE EAST OF WW 519, COOLER  
SURFACE TEMPERATURES AND LESS LOW-LEVEL MOISTURE IS PRESENT WITH  
EASTWARD EXTENT ACROSS CENTRAL AR. RESULTANT INSTABILITY LIKEWISE  
WANES INTO CENTRAL AR. COUPLED WITH THE LOSS OF DIURNAL HEATING  
WHICH SHOULD FURTHER REDUCE ALREADY WEAK INSTABILITY, THE SMALL  
SPATIAL SEVERE THREAT TO THE EAST OF WW 519 MAY BECOME TOO MARGINAL  
OVER THE NEXT SEVERAL HOURS TO JUSTIFY A NEW WW IN CENTRAL AR.  
 
..GLEASON.. 12/04/2017  
   
..PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT
 
 
ATTN...WFO...LZK...SHV...TSA...OUN...  
 
LAT...LON 34869577 35509514 36459470 36459248 35419248 33959344  
33619418 34029517 33979592 34489610 34869577  
 
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