317  
ACUS02 KWNS 241725  
SWODY2  
SPC AC 241724  
 
DAY 2 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK  
1224 PM CDT MON SEP 24 2018  
 
VALID 251200Z - 261200Z  
 
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE MIDDLE  
AND UPPER MISSISSIPPI VALLEY INTO THE GREAT LAKES AND OHIO VALLEY...  
   
..SUMMARY
 
 
SEVERE THUNDERSTORMS ARE POSSIBLE TUESDAY AFTERNOON INTO TUESDAY  
NIGHT ACROSS PARTS OF THE MIDDLE MISSISSIPPI AND OHIO VALLEYS INTO  
THE GREAT LAKES REGION.  
   
..SYNOPSIS
 
 
A BROAD SYNOPTIC UPPER TROUGH CURRENTLY SITUATED FROM THE NORTHERN  
ROCKIES THROUGH NORTHERN HIGH PLAINS IS FORECAST TO AMPLIFY AS IT  
CONTINUES EAST INTO THE UPPER MS VALLEY AND GREAT LAKES TUESDAY AND  
TUESDAY NIGHT. THIS FEATURE SHOULD BE ACCOMPANIED BY MODEST  
CYCLOGENESIS OVER THE UPPER GREAT LAKES, AND BY MID AFTERNOON A COLD  
FRONT WILL LIKELY EXTEND FROM THE DEVELOPING CYCLONE OVER WI  
SOUTHWEST THROUGH IA INTO THE TX PANHANDLE. THIS BOUNDARY WILL  
ADVANCE EAST AND SOUTHEAST REACHING THE LOWER GREAT LAKES AND  
EXTENDING SOUTHWEST THROUGH CENTRAL TX BY THE END OF THIS PERIOD.  
AHEAD OF THE PRIMARY SYNOPTIC TROUGH A SHORTWAVE TROUGH NOW OVER THE  
TN VALLEY WILL REACH THE NORTHEAST STATES EARLY TUESDAY MORNING. A  
WARM FRONT WILL DEVELOP NORTHWARD THROUGH THE OH VALLEY AND INTO THE  
GREAT LAKES DURING THE DAY.  
 
...MIDDLE MISSISSIPPI VALLEY INTO THE OHIO VALLEY AND GREAT  
LAKES...  
 
INITIAL LOW-LEVEL JET ASSOCIATED WITH A NORTHEAST-EJECTING SHORTWAVE  
TROUGH WILL ADVANCE THROUGH THE NORTHEAST STATES EARLY TUESDAY  
ACCOMPANIED BY WIDESPREAD SHOWERS AND A FEW THUNDERSTORMS. IN WAKE  
OF THIS FEATURE, MODEST SOUTHWESTERLY LOW-LEVEL WINDS WILL PERSIST  
IN THE OH VALLEY WARM SECTOR CONTRIBUTING TO NORTHWARD ADVECTION OF  
RICHER LOW LEVEL MOISTURE WITH DEWPOINTS RISING TO THE MID-UPPER 60S  
F TUESDAY MORNING AS FAR NORTH AS SOUTHERN PORTION OF THE GREAT  
LAKES. SHOWERS AND A FEW THUNDERSTORMS WILL BE POSSIBLE WITHIN THIS  
WEAK WARM ADVECTION REGIME DURING THE DAY. WHILE VERTICAL SHEAR  
THROUGH A DEEP LAYER WILL BE SUFFICIENT FOR ORGANIZED STORMS,  
UNCERTAINTY STILL EXISTS REGARDING THE EVOLUTION OF THE  
THERMODYNAMIC ENVIRONMENT GIVEN EXPECTED WIDESPREAD CLOUDS.  
NEVERTHELESS, THE ADVECTION OF RICHER LOW-LEVEL MOISTURE AND A SOME  
CLOUD BREAKS SHOULD CONTRIBUTE TO AT LEAST 1000-1500 J/KG MLCAPE BY  
MID AFTERNOON, WITH GREATEST BOUNDARY LAYER DESTABILIZATION LIKELY  
ACROSS A PORTION OF THE MIDDLE MS VALLEY. WINDS ALOFT WILL GRADUALLY  
STRENGTHEN FROM THE WEST TUESDAY AFTERNOON WITH APPROACH OF THE  
UPPER TROUGH ALONG WITH AN INCREASE IN THE SOUTHERLY LOW-LEVEL JET  
BY EARLY EVENING. POTENTIAL FOR ORGANIZED SEVERE STORMS SHOULD  
GRADUALLY INCREASE TUESDAY AS DEEP LAYER WINDS STRENGTHEN AND THE  
SURFACE LAYER UNDERGOES AT LEAST MODEST DESTABILIZATION. A FEW  
SUPERCELLS AND BOWING SEGMENTS MAY DEVELOP IN WARM SECTOR, AND  
ADDITIONAL SEVERE STORMS WITH MORE LINEAR ORGANIZATION ARE EXPECTED  
FARTHER WEST ACROSS THE UPPER MS VALLEY ALONG THE COLD FRONT.  
INITIAL PRIMARY THREAT SHOULD BE DAMAGING WIND AND POSSIBLY SOME  
HAIL, BUT AS THE LOW-LEVEL JET STRENGTHENS BY LATE AFTERNOON OR  
EVENING, THE THREAT FOR A FEW TORNADOES SHOULD ALSO INCREASE.  
ACTIVITY WILL SPREAD EAST THROUGH THE OH VALLEY AND GREAT LAKES  
REGION DURING THE EVENING AND INTO THE OVERNIGHT. GIVEN  
UNCERTAINTIES RELATED TO EVOLUTION OF THE THERMODYNAMIC ENVIRONMENT,  
WILL MAINTAIN GENERAL 15% PROBABILITIES THIS OUTLOOK, BUT AN UPGRADE  
TO HIGHER PROBABILITIES WILL BE CONSIDERED IN DAY 1 UPDATES ACROSS A  
PORTION OF THIS REGION.  
   
..MAXIMUM RISK BY HAZARD
 
 
TORNADO: 5% - SLIGHT  
WIND: 15% - SLIGHT  
HAIL: 15% - SLIGHT  
 
..DIAL.. 09/24/2018  
 

 
 
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