612  
ACUS01 KWNS 290538  
SWODY1  
SPC AC 290537  
 
DAY 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK  
1237 AM CDT SAT APR 29 2017  
 
VALID 291200Z - 301200Z  
 
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM CENTRAL  
TEXAS TO SOUTHERN MISSOURI...  
 
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM SOUTH CENTRAL  
TEXAS TO SOUTHWEST OHIO...  
 
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM SOUTH TEXAS  
TO THE NORTHERN MIDDLE ATLANTIC...  
   
..SUMMARY
 
 
SEVERE THUNDERSTORMS ARE EXPECTED FROM PARTS OF SOUTH CENTRAL TEXAS  
NORTHEASTWARD TO PORTIONS OF THE OHIO VALLEY/NORTHERN MIDDLE  
ATLANTIC REGION SATURDAY INTO SATURDAY NIGHT. THESE STORMS WILL BE  
CAPABLE OF LARGE HAIL, DAMAGING WINDS, AND A FEW TORNADOES.  
   
..DISCUSSION
 
 
EARLY-MORNING WATER VAPOR IMAGERY DEPICTS A WELL-DEFINED UPPER LOW  
NEAR THE 4-CORNERS REGION, DRIFTING SLOWLY SOUTHEAST IN LINE WITH  
THE LATEST MODEL GUIDANCE. THIS FEATURE IS FORECAST TO SHIFT INTO  
THE SOUTHERN HIGH PLAINS REGION BY THE END OF THE DAY1 PERIOD AS  
STRONGEST MID-LEVEL FLOW FINALLY ROTATES THROUGH THE BASE OF THE  
TROUGH INTO NORTHWEST TX/WESTERN OK. GIVEN THIS SCENARIO, STRONGEST  
MID-LEVEL HEIGHT FALLS WILL NOT SPREAD INTO WEST TX UNTIL LATE  
AFTERNOON. AS A RESULT, LARGE-SCALE FORCING, FOR ASCENT, WILL BE  
NEGLIGIBLE ACROSS MUCH OF THE WARM SECTOR THROUGH THE PERIOD. IT  
APPEARS WIDESPREAD CONVECTION WILL CONCENTRATE ALONG A STATIONARY  
FRONTAL ZONE ORIENTED FROM EASTERN OK INTO THE OH VALLEY AND ALONG  
THE COLD FRONT AS IT SURGES EASTWARD ACROSS OK/TX THEN INTO THE  
LOWER MS VALLEY SATURDAY NIGHT.  
 
AT 29/05Z...A NARROW CORRIDOR OF WIDESPREAD THUNDERSTORMS HAS  
EVOLVED ALONG THE AFOREMENTIONED FRONTAL ZONE FROM NORTHERN OK,  
NORTHEAST INTO SOUTHERN OH. WARM ADVECTION SHOULD MAINTAIN THIS  
ZONE OF CONVECTION THROUGH SUNRISE SATURDAY MORNING. HAIL MAY BE  
THE GREATEST SEVERE RISK WITH THIS ACTIVITY, THOUGH VERY HEAVY RAIN  
MAY ULTIMATELY BECOME AN ISSUE ALONG THIS FRONT AS TRAINING  
THUNDERSTORMS ALLOW THE SURFACE BOUNDARY TO OSCILLATE A BIT THROUGH  
THE PERIOD. BY 12Z SATURDAY, STRONG/SEVERE SQUALL LINE IS EXPECTED  
TO EVOLVE ALONG THE COLD FRONT AS IT SURGES ACROSS OK/NORTHWEST TX.  
DAMAGING WINDS COULD EVOLVE WITH THIS ACTIVITY, IN ADDITION TO SOME  
HAIL THREAT.  
 
GIVEN THE SLOW EASTWARD MOVEMENT OF THE UPPER LOW, AND THE LACK OF  
MEANINGFUL FORCING ACROSS THE WARM SECTOR, LINEAR CONVECTION SHOULD  
BE THE PRIMARY STORM MODE ALONG THE COLD FRONT, THOUGH STRONG SHEAR  
PROFILES DO FAVOR SUSTAINED ROTATING UPDRAFTS, ESPECIALLY  
IMMEDIATELY AHEAD OF THE SURFACE LOW/WARM FRONT. EVEN SO, WARM  
FRONTAL CONVECTION MAY STRUGGLE TO MAINTAIN SUPERCELL  
CHARACTERISTICS ACROSS THE MID MS VALLEY DUE TO EXTENSIVE  
PRECIPITATION/STORM MERGERS. IT APPEARS AN EXTENSIVE FRONTAL MCS  
WILL ADVANCE ACROSS THE SOUTHERN PLAINS INTO THE MID/LOWER MS VALLEY  
REGION DURING THE LATTER HALF OF THE PERIOD. LARGE HAIL AND  
DAMAGING WINDS ARE THE PRIMARY THREATS, THOUGH A FEW TORNADOES CAN  
NOT BE RULED OUT IF EMBEDDED SUPERCELLS EVOLVE ALONG THE SQUALL  
LINE, OR WARM FRONT.  
 
..DARROW/COHEN.. 04/29/2017  
 

 
 
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