822  
ACUS03 KWNS 140829  
SWODY3  
SPC AC 140828  
 
DAY 3 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK  
0228 AM CST THU DEC 14 2017  
 
VALID 161200Z - 171200Z  
 
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS A SMALL  
PART OF SOUTHEAST TEXAS AND SOUTHWEST LOUISIANA SATURDAY NIGHT TO  
EARLY SUNDAY MORNING...  
   
..SUMMARY
 
 
THUNDERSTORMS SHOULD DEVELOP ACROSS THE MIDDLE AND UPPER TEXAS  
COASTAL REGION BY SATURDAY EVENING AND SPREAD INTO EAST TEXAS,  
LOUISIANA AND SOUTHWEST MISSISSIPPI THROUGH EARLY SUNDAY MORNING. A  
MARGINAL RISK FOR SEVERE STORMS MAY DEVELOP SATURDAY NIGHT ACROSS  
SOUTHEAST TEXAS INTO SOUTHWEST LOUISIANA.  
   
..MIDDLE AND UPPER TX COASTAL REGION TO LA/SOUTHWEST MS
 
 
A PACIFIC TROUGH MOVING INLAND ACROSS BRITISH COLUMBIA AND THE  
WESTERN STATES IS EXPECTED TO UNDERGO FURTHER AMPLIFICATION AND  
DEEPENING THROUGH THE ROCKIES AND NORTHWEST MEXICO. THIS EVOLUTION  
IN THE UPPER-AIR PATTERN WILL SUPPORT A NORTHEAST EJECTION OF THE  
DAY 2 NORTHERN MEXICO SHORTWAVE TROUGH THROUGH TX TO EASTERN TX/OK  
AND AR/LA BY 12Z SUNDAY. MODELS DIFFER SOME WITH THE TIMING, BUT  
ALL AGREE THAT THIS TROUGH WHILE WEAKENING SHOULD BECOME NEUTRAL TO  
A SLIGHT NEGATIVE TILT SATURDAY NIGHT. WITH THE APPROACH OF THIS  
TROUGH, AN AREA OF LOW PRESSURE WILL LIKELY DEVELOP NEAR THE MIDDLE  
TX COAST SATURDAY EVENING AND TRACK NORTH/NORTHEAST TO THE MARGINAL  
RISK AREA LATER SATURDAY NIGHT.  
 
EASTERLY LOW-LEVEL WINDS ACROSS THE NORTHERN GULF AND ADJACENT  
STATES WILL MAINTAIN WEAKER BOUNDARY LAYER MOISTURE ACROSS MUCH OF  
THE DISCUSSION AREA UNTIL SATURDAY EVENING. THEREAFTER,  
STRENGTHENING SOUTHERLY LOW-LEVEL WINDS EAST OF THE SURFACE LOW INTO  
SOUTHEAST TX AND SOUTHWEST LA WILL RESULT IN AN INCREASE IN WARM  
ADVECTION ATOP A STABLE BOUNDARY LAYER ACROSS INLAND AREAS OF THE TX  
COASTAL PLAIN TO THE LOWER MS VALLEY. THESE FACTORS SUGGEST MOST OF  
THE THUNDERSTORM POTENTIAL SATURDAY EVENING/OVERNIGHT WILL BE  
ELEVATED. HOWEVER, GIVEN THE APPROACH OF THE SURFACE LOW TO THE  
MARGINAL RISK AREA, FORECAST SOUNDINGS SUGGEST THE POTENTIAL FOR  
SUFFICIENT MOISTENING (SURFACE DEW POINTS INTO THE MIDDLE 60S) FOR  
SURFACE-BASED PARCELS AND THE OCCURRENCE OF STRONG TO SEVERE STORMS  
BETWEEN 17/06-12Z. THERE IS SOME INDICATION, GIVEN WEAK LAPSE  
RATES, THAT BUOYANCY MAY NOT BECOME DEEP ENOUGH FOR LIGHTNING  
PRODUCTION. HOWEVER, THE STRENGTH OF DEEP-LAYER AND LOW-LEVEL SHEAR  
(SURFACE-1-KM SHEAR OF 30-35 KT) WILL BE SUFFICIENT FOR ORGANIZED  
STORMS/SUPERCELLS WITH LOW-LEVEL ROTATION LATER SATURDAY EVENING  
INTO THE OVERNIGHT. OVERALL WEAK INSTABILITY SHOULD LIMIT THE  
SEVERE-WEATHER THREAT, AND THUS WILL ONLY INTRODUCE LOW SEVERE  
PROBABILITIES AT THIS TIME.  
 
..PETERS.. 12/14/2017  
 

 
 
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