168  
ACUS01 KWNS 131945  
SWODY1  
SPC AC 131944  
 
DAY 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK  
0244 PM CDT THU JUN 13 2024  
 
VALID 132000Z - 141200Z  
 
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS IN SOUTHERN  
IA...NORTHERN MO...AND NORTHERN/CENTRAL IL...  
   
..SUMMARY
 
 
SEVERE THUNDERSTORMS ARE EXPECTED LATE THIS AFTERNOON AND EARLY  
EVENING ACROSS PARTS OF SOUTHERN IOWA INTO NORTHERN MISSOURI AND  
NORTHERN/CENTRAL ILLINOIS. VERY LARGE HAIL, DESTRUCTIVE WIND GUSTS,  
AND A COUPLE OF TORNADOES ALL APPEAR POSSIBLE. A BROADER CORRIDOR OF  
SEVERE HAIL/WIND POTENTIAL WILL EXTEND FROM PORTIONS OF THE  
SOUTHERN/CENTRAL HIGH PLAINS TO THE GREAT LAKES.  
   
..20Z UPDATE
 
 
OVERALL PRIOR FORECAST APPEARS REASONABLY ON-TRACK. ONLY MINOR  
CHANGES WERE MADE BASED ON LATEST OBSERVATIONAL TRENDS. THIS WAS  
LARGELY TO THE WEST/NORTH SIDE OF ONGOING CONVECTION/FRONTAL  
PLACEMENT FROM MI TO IA AND IN SOUTH FL. FOR ADDITIONAL SHORT-TERM  
FORECAST INFORMATION, PLEASE SEE MCD 1248 REGARDING THE  
SOUTH-CENTRAL HIGH PLAINS AND MCD 1249 FOR THE MID-MS TO LOWER MO  
VALLEYS.  
 
..GRAMS.. 06/13/2024  
   
PREV DISCUSSION
 
/ISSUED 1128 AM CDT THU JUN 13 2024/  
   
..GREAT LAKES
 
 
A MID-LEVEL SHORTWAVE TROUGH WITH ASSOCIATED WESTERLY  
MID/UPPER-LEVEL JET WILL MOVE EASTWARD ACROSS THE UPPER MIDWEST AND  
GREAT LAKES TODAY. AN ATTENDANT SURFACE COLD FRONT WILL LIKEWISE  
SWEEP EASTWARD ACROSS THESE REGIONS THROUGH THIS EVENING, WITH THE  
PRIMARY SURFACE CYCLONE FORECAST TO REMAIN IN CANADA. PARTLY CLOUDY  
SKIES THIS MORNING SHOULD GIVE WAY TO BETTER OPPORTUNITY FOR DIURNAL  
HEATING THIS AFTERNOON. INCREASING LOW-LEVEL CONVERGENCE ALONG THE  
FRONT, ALONG WITH ASCENT ASSOCIATED WITH SHORTWAVE TROUGH/MID-LEVEL  
JET, SHOULD ENCOURAGE CONVECTIVE DEVELOPMENT ALONG/NEAR THE FRONT BY  
MID AFTERNOON ACROSS PARTS OF LOWER MI INTO NORTHERN IL/IN AND  
VICINITY. SUFFICIENT INSTABILITY AND DEEP-LAYER SHEAR ARE FORECAST  
TO SUPPORT ROBUST THUNDERSTORMS WITH A THREAT FOR SCATTERED DAMAGING  
WINDS AND SEVERE HAIL. THE MAGNITUDE OF THE SEVERE THREAT WILL BE  
DEPENDENT ON HOW MUCH INSTABILITY CAN DEVELOP, WITH DIFFERENCES  
REMAINING IN HIGH-RESOLUTION GUIDANCE REGARDING BOTH HOW MUCH  
CONVECTION DEVELOPS, AND HOW INTENSE IT WILL BECOME. REGARDLESS,  
SOME SEVERE THREAT REMAINS APPARENT, AND THE MARGINAL/SLIGHT RISKS  
HAVE BEEN MAINTAINED ACROSS THIS REGION WITH MINIMAL CHANGES FOR  
THIS UPDATE.  
   
..MID MISSISSIPPI VALLEY
 
 
A SURFACE COLD FRONT IS PROGGED TO SAG MORE SLOWLY  
SOUTH-SOUTHEASTWARD ACROSS THE MID MS VALLEY TODAY, WITH BETTER  
FORCING ALOFT GENERALLY REMAINING TO THE NORTH ACROSS THE UPPER  
MIDWEST AND GREAT LAKES. A RATHER MOIST LOW-LEVEL AIRMASS, WITH  
SURFACE DEWPOINTS GENERALLY IN THE UPPER 60S TO LOW 70S, WILL REMAIN  
ALONG/SOUTH OF THIS BOUNDARY ACROSS THE MID MS VALLEY. ROBUST  
DAYTIME HEATING OF THIS AIRMASS, ALONG WITH STEEP MID-LEVEL LAPSE  
RATES, WILL PROMOTE MODERATE TO STRONG INSTABILITY (MLCAPE 2500-3500  
J/KG) BY MID/LATE AFTERNOON FROM SOUTHEAST NE/NORTHEAST KS INTO  
SOUTHERN IA/NORTHERN MO AND VICINITY. WARM MID-LEVEL TEMPERATURES  
NOTED ON AREA 12Z SOUNDINGS (700 MB TEMPERATURES OF 13+ C) WILL  
LIKELY INHIBIT ROBUST CONVECTIVE DEVELOPMENT FOR MUCH OF THE DAY,  
UNTIL SURFACE TEMPERATURES REACH AT LEAST THE LOW 90S AND FINALLY  
ERODE LINGERING MLCIN.  
 
EXPLOSIVE THUNDERSTORM DEVELOPMENT IS LIKELY BY 20-22Z ALONG/NEAR  
THE FRONT, AS STRONG INSTABILITY COMBINES WITH ENHANCED DEEP-LAYER  
SHEAR TO SUPPORT AN THREAT FOR MULTIPLE INTENSE SUPERCELLS. VERY  
LARGE HAIL OF AT LEAST 2-3 INCHES IN DIAMETER, AND PERHAPS A COUPLE  
TORNADOES, WILL BE A THREAT WITH THESE INITIALLY DISCRETE  
SUPERCELLS. WITH MID-LEVEL WESTERLY FLOW LARGELY PARALLEL TO THE  
SURFACE BOUNDARY, A QUICK TRANSITION/UPSCALE GROWTH INTO ONE OR MORE  
BOWING CLUSTERS SEEMS LIKELY BY EARLY EVENING. THIS ACTIVITY SHOULD  
TEND TO HAVE A GREATER THREAT FOR SEVERE/DAMAGING WINDS, INCLUDING  
THE POTENTIAL FOR SOME SIGNIFICANT GUSTS OF 75-80 MPH. THE SEVERE  
WIND/HAIL THREAT SHOULD CONTINUE IN A RELATIVELY NARROW CORRIDOR  
THIS EVENING ACROSS THE MID MS VALLEY, BEFORE INCREASING MLCIN AND  
NOCTURNAL COOLING GRADUALLY REDUCE THE OVERALL SEVERE RISK TONIGHT.  
   
..KANSAS INTO THE SOUTHERN/CENTRAL HIGH PLAINS
 
 
A HOT AND DEEPLY MIXED AIRMASS IS ANTICIPATED ALONG/NEAR THE FRONT  
ACROSS KS INTO THE SOUTHERN/CENTRAL HIGH PLAINS. THIS REGION WILL  
GENERALLY BE DISPLACED TO THE SOUTH OF STRONGER FORCING ALOFT, AND  
WARM MID-LEVEL TEMPERATURES MAY INHIBIT CONVECTION FOR MUCH OF THE  
DAY. STILL, MOST GUIDANCE SUGGESTS ISOLATED TO SCATTERED  
THUNDERSTORMS WILL DEVELOP WITH A VERY WELL MIXED BOUNDARY LAYER AND  
STEEPENED LOW/MID-LEVEL LAPSE RATES. SEVERE/DAMAGING DOWNDRAFT WINDS  
APPEAR TO BE THE MAIN THREAT WITH THIS ACTIVITY, ALTHOUGH SOME HAIL  
MAY ALSO OCCUR WITH ANY MARGINAL SUPERCELL STRUCTURES THAT CAN FORM.  
BASED ON LATEST GUIDANCE TRENDS, THE SLIGHT RISK HAS BEEN EXPANDED  
WESTWARD TO INCLUDE MORE OF WESTERN KS AND EASTERN CO. ISOLATED  
SIGNIFICANT SEVERE WIND GUSTS (75+ MPH) MAY OCCUR WITH ANY LOOSELY  
ORGANIZED CLUSTERS ACROSS KS. BUT, WEAKER DEEP-LAYER SHEAR COMPARED  
WITH LOCATIONS FARTHER EAST SUGGESTS THE OVERALL SEVERE THREAT WILL  
PROBABLY REMAIN FAIRLY ISOLATED.  
   
..SOUTH FLORIDA
 
 
A LOOSELY ORGANIZED BAND OF CONVECTION IS ONGOING ACROSS PARTS OF  
SOUTH FL. WHILE MID-LEVEL LAPSE RATES ARE EXPECTED TO REMAIN POOR,  
SUFFICIENT INSTABILITY AND DEEP-LAYER SHEAR MAY SUPPORT OCCASIONAL  
STRONG/GUSTY WINDS WITH THE MORE ROBUST ACTIVITY THIS AFTERNOON AND  
EARLY EVENING. A BRIEF TORNADO OR TWO MAY ALSO OCCUR GIVEN MODESTLY  
ENHANCED LOW-LEVEL FLOW.  
 

 
 
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