018  
ACUS03 KWNS 260721  
SWODY3  
SPC AC 260721  
 
DAY 3 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK  
0221 AM CDT FRI MAY 26 2017  
 
VALID 281200Z - 291200Z  
 
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF  
THE SOUTHERN PLAINS...ARKLATEX...MID MISSISSIPPI VALLEY AND OHIO  
VALLEY...  
 
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OUTSIDE OF THE  
SLIGHT RISK ACROSS PARTS OF THE SOUTHERN PLAINS...ARKLATEX...MID  
MISSISSIPPI VALLEY...OHIO VALLEY...GREAT LAKES...CENTRAL  
APPALACHIANS AND CAROLINAS...  
   
..SUMMARY
 
 
SCATTERED SEVERE THUNDERSTORMS WITH A THREAT FOR LARGE HAIL, WIND  
DAMAGE AND A FEW TORNADOES WILL BE POSSIBLE ON SUNDAY ACROSS PARTS  
OF THE MID MISSISSIPPI AND OHIO VALLEYS. LARGE HAIL AND WIND DAMAGE  
WILL ALSO BE POSSIBLE ACROSS PARTS OF THE SOUTHERN PLAINS AND  
ARKLATEX.  
   
..MID MISSISSIPPI VALLEY/OHIO VALLEY
 
 
AN UPPER-LEVEL TROUGH IS FORECAST TO MOVE EASTWARD INTO THE MID TO  
UPPER MISSISSIPPI VALLEY ON SUNDAY AS A COLD FRONT ADVANCES  
SOUTHEASTWARD INTO THE OHIO AND MID MISSISSIPPI VALLEYS. A MOIST  
AIRMASS IS FORECAST AHEAD OF THE FRONT WITH SURFACE DEWPOINTS IN THE  
MID TO UPPER 60S F. THIS SHOULD BE ENOUGH FOR THE DEVELOPMENT OF  
MODERATE INSTABILITY BY AFTERNOON ACROSS PRATS OF WESTERN TENNESSEE,  
KENTUCKY, SOUTHERN INDIANA AND OHIO. MODEL FORECASTS ALONG THIS  
CORRIDOR GENERALLY DEVELOP SCATTERED CONVECTION DURING THE LATE  
AFTERNOON AS THE UPPER-LEVEL TROUGH APPROACHES. GFS FORECAST  
SOUNDINGS AT 00Z/MONDAY FROM MEMPHIS, TENNESSEE NORTHEASTWARD TO  
LOUISVILLE, KENTUCKY SHOW MLCAPE VALUES OF 2000 TO 2500 J/KG WITH  
0-6 KM SHEAR VALUES FROM 40 TO 50 KT. IF THE CONVECTION CAN DEVELOP  
INTO CLUSTERS WITH DISCRETE CELLS, THEN THE ENVIRONMENT WOULD  
SUPPORT SUPERCELLS WITH LARGE HAIL, WIND DAMAGE AND POSSIBLY A  
TORNADO THREAT. IF CONVECTION TENDS TO ORGANIZE INTO LINE SEGMENTS,  
WIND DAMAGE COULD BE THE PRIMARY THREAT. A TENDENCY TO GO LINEAR MAY  
BE THE MORE LIKELY OUTCOME DUE TO UNIDIRECTIONAL WIND PROFILES AND  
THE DEEP-LAYER SHEAR VECTORS BEING SOMEWHAT PARALLEL TO THE  
BOUNDARY. THE EXACT CORRIDOR WITH THE HIGHEST SEVERE THREAT WILL  
LIKELY DEPEND UPON THE POSITION OF THE COLD FRONT BY LATE SUNDAY  
AFTERNOON.  
   
..SOUTHERN PLAINS/ARKLATEX
 
 
WESTERLY TO WEST-SOUTHWESTERLY MID-LEVEL FLOW IS FORECAST TO BE IN  
PLACE ACROSS THE SOUTHERN PLAINS AND ARKLATEX ON SUNDAY AS A COLD  
FRONT ADVANCES SOUTHEASTWARD ACROSS THE REGION. AHEAD OF THE FRONT,  
SURFACE DEWPOINTS ARE FORECAST TO BE IN THE UPPER 60S AND LOWER 70S  
F WITH A CORRIDOR OF MODERATE TO STRONG INSTABILITY IN PLACE BY  
AFTERNOON. MODEL FORECASTS APPEAR TO DEVELOP CONVECTION ALONG THE  
FRONT AND ON THE COOL SIDE OF THE FRONT SUNDAY AFTERNOON AND  
EVENING. GFS FORECAST SOUNDINGS NEAR THE FRONT AT 00Z/MONDAY ACROSS  
THE TEXAS HILL COUNTRY AND ARKLATEX SHOW STRONG INSTABILITY (MLCAPE  
OF 2500 TO 4000 J/KG) WITH 0-6 KM SHEAR IN THE 30 TO 40 KT RANGE.  
THIS COMBINED WITH STEEP LAPSE RATES IN THE 500-300 MB LAYER WOULD  
SUPPORT SUPERCELL DEVELOPMENT WITH ISOLATED LARGE HAIL. WIND DAMAGE  
WOULD ALSO BE POSSIBLE ESPECIALLY WITH STORMS THAT CAN PERSIST AND  
DEVELOP MATURE DOWNDRAFTS.  
 
..BROYLES.. 05/26/2017  
 

 
 
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