524  
ACUS03 KWNS 190812  
SWODY3  
SPC AC 190811  
 
DAY 3 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK  
0211 AM CST THU JAN 19 2017  
 
VALID 211200Z - 221200Z  
 
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM LOUISIANA AND  
MISSISSIPPI EASTWARD TO GEORGIA...  
 
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SURROUNDING THE  
SLIGHT RISK AREA...  
   
..SUMMARY
 
 
A FEW EPISODES OF SEVERE STORMS WILL BE POSSIBLE FROM SATURDAY  
MORNING THROUGH SUNDAY MORNING ACROSS A BROAD AREA OF THE LOWER  
MISSISSIPPI VALLEY AND THE SOUTHEAST STATES.  
   
..LOWER MISSISSIPPI VALLEY TO THE NORTHEAST GULF COAST
 
 
A STRONG MID-UPPER TROUGH, NOW SOUTH OF THE ALEUTIANS, WILL REACH  
THE CA COAST AND NORTHWEST MEXICO BY DAY 2 (FRIDAY), AND CONTINUE  
EASTWARD ACROSS THE SOUTHERN PLAINS TO THE LOWER MS VALLEY BY  
SATURDAY NIGHT/SUNDAY MORNING (END OF DAY 3). THERE ARE SOME  
DISAGREEMENTS AMONG THE OPERATIONAL MODELS, WITH THE NAM APPEARING  
TO REFLECT SOME CONVECTIVE FEEDBACK AND EASTWARD DEVELOPMENT OF THE  
SYNOPTIC CYCLONE TOO FAST COMPARED TO THE GFS/ECMWF. WITHOUT THE  
FEEDBACK, LOW-LEVEL MASS RESPONSE/FLOW SHOULD REMAIN RELATIVELY WEAK  
DURING THE DAY SATURDAY ACROSS LA/MS IN THE MAIN PART OF THE WARM  
SECTOR. THE PRIMARY SYNOPTIC CYCLONE AND ASSOCIATED LARGE-SCALE  
FORCING FOR ASCENT WILL APPROACH THE MS RIVER BY THE END OF THE  
PERIOD.  
 
COMPLICATING FACTORS THIS PERIOD WILL BE ANY LINGERING INFLUENCE OF  
ONGOING CONVECTION SATURDAY MORNING FROM MS INTO AL, AND A SOMEWHAT  
NEBULOUS FOCUS FOR ADDITIONAL STORMS DURING THE AFTERNOON ACROSS  
LA/MS (WELL AHEAD OF THE SYNOPTIC WAVE/COLD FRONT). ANY STORMS THAT  
FORM HERE WILL DO SO IN AN ENVIRONMENT WITH STEEP MIDLEVEL LAPSE  
RATES, MODERATE BUOYANCY, AND SUFFICIENT DEEP-LAYER SHEAR FOR  
SUPERCELLS CAPABLE OF PRODUCING LARGE HAIL (POTENTIALLY SOME VERY  
LARGE) AND DAMAGING WINDS. THE STRONGER LOW-LEVEL WIND PROFILES ARE  
EXPECTED FARTHER EAST AND OVERNIGHT IN ASSOCIATION WITH A LEAD SPEED  
MAX PROGRESSING INLAND FROM THE GULF. ENHANCEMENT TO LOW-LEVEL  
SHEAR/SRH FROM SOUTH/SOUTHEAST AL INTO THE FL PANHANDLE AND  
SOUTHWEST GA WILL FAVOR SUPERCELLS WITH DAMAGING WINDS AND  
POTENTIALLY SOME TORNADO RISK, DEPENDING ON THE DETAILS ON THE  
LOW-LEVEL SHEAR AND NEAR-GROUND LAPSE RATES INLAND.  
 
WILL OPT TO MAINTAIN A RATHER BROAD 15%/SLIGHT RISK AREA IN THIS  
UPDATE, THOUGH PORTIONS OF THE OUTLOOK AREA MAY NEED TO BE  
CONSIDERED FOR HIGHER COVERAGE/INTENSITY PROBABILITIES ONCE  
UNCERTAINTIES ARE REDUCED.  
 
..THOMPSON.. 01/19/2017  
 

 
 
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