415  
ACUS01 KWNS 270544  
SWODY1  
SPC AC 270542  
 
DAY 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK  
1242 AM CDT MON MAR 27 2017  
 
VALID 271200Z - 281200Z  
 
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FOR PARTS OF  
WESTERN KENTUCKY INTO WESTERN AND MIDDLE TENNESSEE AND NORTHERN  
MISSISSIPPI...  
 
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF  
THE LOWER MISSISSIPPI VALLEY INTO PARTS OF THE TENNESSEE AND LOWER  
OHIO VALLEYS...  
 
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SURROUNDING THE  
SLIGHT RISK...  
   
..SUMMARY
 
 
SEVERE THUNDERSTORMS WILL BE POSSIBLE FROM PARTS OF THE LOWER  
MISSISSIPPI AND TENNESSEE VALLEYS NORTHWARD TO THE OHIO VALLEY TODAY  
INTO THIS EVENING. HAIL AND DAMAGING WINDS WILL BE THE PRIMARY  
SEVERE HAZARDS WITH THE STRONGER STORMS.  
   
..SYNOPSIS
 
 
A VIGOROUS SHORTWAVE TROUGH SUNDAY NIGHT ON WATER-VAPOR IMAGERY OVER  
THE CENTRAL GREAT PLAINS WILL MOVE EASTWARD INTO THE LOWER OH VALLEY  
DURING THE PERIOD. AN ASSOCIATED STRONG BELT OF CYCLONICALLY CURVED  
MID-LEVEL FLOW WILL OVERSPREAD THE LOWER MS VALLEY INTO THE TN AND  
OH VALLEYS. IN THE LOW LEVELS, A NORTHWARD ADVANCING WARM FRONT  
WILL MOVE THROUGH THE TN VALLEY. A WEAK SURFACE LOW WILL DEVELOP  
EAST-NORTHEAST ACROSS THE MS VALLEY INTO THE OH VALLEY AS A COLD  
FRONT MOVES EAST ACROSS PARTS OF THE MID SOUTH BEFORE STALLING OVER  
THE LOWER MS VALLEY.  
   
..PORTIONS OF THE OH-TN-MS VALLEYS
 
 
LOW-LEVEL MOISTURE WILL RETURN NORTH INTO THE MID SOUTH AND OH  
VALLEY WITHIN A WAA REGIME ASSOCIATED WITH A 35-KT LLJ DURING THE  
MORNING. SHOWERS AND ISOLATED THUNDERSTORMS WILL LIKELY BE ONGOING  
NEAR THE MS RIVER AT DAYBREAK AND MOVE DOWNSTREAM INTO TN AND THE  
LOWER OH VALLEY. THERE IS SOME UNCERTAINTY REGARDING THE MAGNITUDE  
OF DESTABILIZATION FARTHER NORTH NEAR THE OH RIVER WHERE CLOUDS AND  
EARLY-DAY CONVECTION MAY LIMIT DESTABILIZATION. NONETHELESS, MODELS  
SHOW A PLUME OF UPPER 50S DEWPOINTS NEAR THE OH RIVER TO THE LOW-MID  
60S IN THE MS DELTA. THE INCREASING MOISTURE COUPLED WITH DIURNAL  
DESTABILIZATION SOUTH AND WEST OF EARLY ACTIVITY WILL PROBABLY  
RESULT IN 1000-1500 J/KG MLCAPE DEVELOPING BY MID AFTERNOON WITH  
WEAK BUOYANCY FORECAST FARTHER NORTH NEAR THE OH RIVER. FORCING FOR  
ASCENT PROVIDED BY THE MID-LEVEL WAVE IN CONJUNCTION WITH  
CONVERGENCE ALONG THE SURFACE BOUNDARY OVER EASTERN AR NORTHWARD TO  
THE OH-MS RIVER CONFLUENCE WILL LIKELY SERVE AS A FOCUS FOR STORM  
DEVELOPMENT DURING THE AFTERNOON. DEEP-LAYER SHEAR IS FORECAST TO  
BE STRONGEST FROM TN SOUTHWARD INTO NORTHERN MS/AL WITH EFFECTIVE  
SHEAR MAGNITUDES 35-50 KT. CELLULAR CLUSTERS OF SUPERCELLS AND  
ORGANIZED MULTICELLS ARE FORECAST WITH HAIL (PERHAPS VERY LARGE WITH  
THE MOST INTENSE STORM OR TWO) AND DAMAGING WINDS THE MAIN THREATS.  
 
FARTHER SOUTHEAST IN THE FREE WARM SECTOR OVER MS AND AL, WEAK  
(30-M) 500-MB HEIGHT FALLS DURING THE DAY COUPLED WITH HEATING AND  
WEAKENING CONVECTIVE INHIBITION MAY RESULT IN STORMS DEVELOPING  
WITHIN CONFLUENCE BANDS IN ABSENCE OF ANY WELL-DEFINED BOUNDARY.  
CONVECTION-ALLOWING MODELS SUGGEST ISOLATED TO WIDELY SCATTERED  
STORMS AND A RISK FOR HAIL AND WIND DAMAGE WILL PROBABLY ACCOMPANY  
THE STRONGER STORMS. THIS ACTIVITY OVER THE DEEP SOUTH AND TN/OH  
VALLEYS WILL LIKELY WEAKEN DURING THE EVENING AS IT MOVES TOWARDS  
THE APPALACHIANS OWING TO THE LOSS OF HEATING AND MOVING EAST OF THE  
INSTABILITY AXIS.  
 
..SMITH/MARSH.. 03/27/2017  
 

 
 
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