013  
FXUS64 KLIX 240927  
AFDLIX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE NEW ORLEANS LA  
427 AM CDT THU AUG 24 2017  
   
SHORT TERM
 
 
TROPICAL STORM HARVEY RE-DEVELOPED LAST NIGHT OVER THE SOUTHERN  
GULF OF MEXICO. THIS STORM WILL NOT ONLY IMPACT THE TEXAS COAST  
THIS WEEK INTO THIS WEEKEND...IT COULD ALSO HAVE AN IMPACT ACROSS  
MUCH OF THE SOUTHERN UNITED STATES. MORE ON HARVEY LATER, BUT  
TODAY WE CAN EXPECT SHOWERS AND STORMS TO DEVELOP THIS AFTERNOON.  
THERE HAS BEEN SOME NOCTURNAL DEVELOPMENT OVER LAKE PONTCHARTRAIN  
AND ALONG THE COAST. SOME THAT HAS ALREADY WEAKENED BUT THINKING  
THAT CONVECTION COULD DEVELOP EARLY OVER THE SOUTHEASTERN PORTIONS  
OF THE FORECAST AREA. OVERNIGHT 6Z SOUNDING SHOWED PW VALUE OF  
2.33 INCHES AND A CONVECTIVE TEMPERATURE OF 88 DEGREES...I AM  
THINKING THAT ONCE THE SUN COMES UP AND WE GET A LITTLE HEATING  
SHOWERS AND STORMS WILL START DEVELOPING. WITH THAT TYPE OF PW,  
SHOWERS AND STORMS WILL BE EFFICIENT RAIN PRODUCERS AND LOCALLY  
HEAVY RAINFALL OR SOME MINOR FLOODING IS POSSIBLE TODAY AS WE  
STILL HAVE A FRONTAL BOUNDARY STALLED OVER THE FORECAST AREA. THIS  
WILL SERVE AS A FOCUS FOR DEVELOPMENT AS WELL. HAVE KEPT POPS THE  
SAME WITH A SOLID 60 PERCENT OVER PORTIONS OF THE FORECAST  
AREA...AND HAVE EXPEDITED THE UPWARD TREND IN POPS THIS MORNING.  
TEMPERATURES SHOULD REACH NEAR 90 TODAY BEFORE CONVECTION STARTS.  
BY TOMORROW, SOME WEAK SUBSIDENCE ON THE OUTER PERIPHERY OF A  
TROPICAL STORM HARVEY AND AN NORTHWARD PUSH OF THE LOW LEVEL  
BOUNDARY BACK TOWARD CENTRAL MISSISSIPPI AND NORTH LOUISIANA  
SHOULD RESULT IN LOWER POP VALUES FOR MUCH OF THE FORECAST AREA.  
   
LONG TERM
 
 
GOING INTO THE WEEKEND THE BIG STORY WILL BE TROPICAL STORM  
HARVEY. LATEST ADVISORY FROM THE NATIONAL HURRICANE CENTER HAS  
HARVEY BECOMING A HURRICANE BEFORE LANDFALL. HARVEY THEN STALLS  
ACROSS SOUTHEAST TEXAS FOR THE MAJORITY OF THE WEEKEND. ALL  
GUIDANCE STILL SUGGEST THIS SOLUTION AND EVEN HAS IT SLOW TO MOVE  
EAST INTO OUR FORECAST AREA. WE MAY NOT SEE THE HEAVIEST SOLID  
AREA OF RAINFALL UNTIL TUESDAY OR WEDNESDAY ACROSS OUR FORECAST  
AREA. THIS IS BECAUSE HARVEY GETS CAUGHT BETWEEN TWO RIDGES  
STALLING IT OVER TEXAS FOR A FEW DAYS...AND IT HAS TO WAIT FOR A  
TROUGH TO DIG IN OVER THE EASTERN UNITED STATES TO PULL IT OUT  
ACROSS THE COUNTRY. HAVE MAINTAINED THE FORECAST FOR THE MOST  
PART. HAVE ADJUSTED TEMPERATURES IN THE LONG RANGE AND ADJUSTED  
POPS IN THE LONG RANGE TO SHOW THE TRENDS IN GUIDANCE. JUST A NOTE  
HERE...JUST BECAUSE WE POSSIBLY WON'T SEE THE HEAVIEST RAIN FROM  
THIS COMPLICATED PATTERN UNTIL EARLY NEXT WEEK DOES NOT MEAN THAT  
HEAVY RAINFALL IS NOT POSSIBLE THIS WEEKEND WITH ANY SHOWER OR  
STORM. THERE WILL BE PLENTY OF MOISTURE AROUND THE AREA WITH A  
STALLED BOUNDARY IN PLACE OVER THE AREA. DO NOT LET YOUR GUARD  
DOWN. LOCALLY HEAVY RAINFALL WILL BE POSSIBLE EACH AND EVERY DAY  
STARTING SATURDAY AND POSSIBLY LASTING THROUGH WEDNESDAY. THERE IS  
A LARGE DEGREE OF UNCERTAINTY IN THE FORECAST FOR NEXT WEEK, SO  
THE FORECAST COULD CHANGE DRAMATICALLY OVER THE NEXT FEW DAYS  
 

 
   
AVIATION
 
 
BETTER CHANCE AT AREAL CONVECTIVE COVERAGE TO INCLUDE TEMPO GROUPS  
FOR MAINLY AFTERNOON CONVECTION THIS AFTERNOON AND EVENING. WILL  
HAVE TO CLOSELY MONITOR BANDING BEHAVIOR ON OUTER BANDS OF HARVEY,  
WHICH MAY MOVE INTO KHUM AND POSSIBLY INTO THE NEW ORLEANS METRO  
AREA OVERNIGHT INTO FRIDAY MORNING. OTHERWISE, VFR CONDITIONS  
EXPECTED OUTSIDE CONVECTION. GUST POTENTIAL APPEARS LOW,  
GENERALLY 10-15 KTS FROM WEAK OUTFLOW GUSTS FEATURES. 24/RR  
 

 
   
MARINE
 
 
GRADUAL INCREASE IN SEAS WITH SWELL GENERATION FROM HARVEY THROUGH  
THE WEEKEND. PERIODS SHOULD ATTAIN 8-10 SECONDS FRIDAY THEN SLOWLY  
ERODE INTO 6 SECONDS FOR THE WEEKEND. THIS WILL SUPPORT A SW GROUND  
SWELL THAT WILL BE INTERSECTING A SE TO E WIND WAVE FOR STEEP SEA  
STATE FOR MUCH OF THE WEEKEND INTO EARLY NEXT WEEK. 24/RR  
 

 
   
SOUNDING DISCUSSION
 
 
06Z SPECIAL RELEASE SOUNDING IN SUPPORT OF TROPICAL STORM HARVEY  
MODELING WENT OFF WITHOUT A HITCH. VERY LIGHT WINDS THROUGHOUT KEPT  
MUCH OF THE FLIGHT WITHIN 2 MILES OF THE STATION BUT MANAGED TO  
TERMINATE OVER LAKE PONTCHARTRAIN ABOUT 4 MILES SE OF THE MOUTH OF  
THE TCHEFUNCTE RIVER, ABOUT 18 MILES DOWNRANGE AT AN ALTITUDE OF  
18.9 MILES AT THE 11.3 MB LEVEL. VERY SOGGY AIR MASS WITH A  
PRECIPITABLE WATER NOW UP TO 2.33 INCHES, WHICH CAN SEE EFFICIENT  
RAIN RATES TODAY, PARTICULARLY WITH SLOW-MOVING NATURE OF ANY STORMS  
THAT DO FORM. SHOWALTER IS AN UNSTABLE -3 IN THE MIDDLE OF THE NIGHT  
WITH A LIFTED INDEX OF -7. CHAP SHOWS A 50% POP WITH RAIN POTENTIAL  
IN THE 5.72-7.09 INCH RANGE. AVERAGE WINDS THROUGHOUT THE COLUMN WAS  
7 KNOTS. 24/RR  
 

 
   
DECISION SUPPORT
 
 
DSS CODE...BLUE.  
DEPLOYED...NONE.  
ACTIVATION...SPECIAL UPPER AIR RELEASES AT 06Z/18Z.  
ACTIVITIES...MONITORING TROPICAL STORM HARVEY..  
 
DECISION SUPPORT SERVICES (DSS) CODE LEGEND  
GREEN = NO WEATHER IMPACTS THAT REQUIRE ACTION  
BLUE = LONG FUSED WATCH/WARNING/ADVISORY IN EFFECT OR HIGH  
VISIBILITY EVENT  
YELLOW = HEIGHTENED IMPACTS WITH SHORT FUSED  
WATCH/WARNING/ADVISORY ISSUANCES; RADAR SUPPORT  
ORANGE = HIGH IMPACTS - SLIGHT TO MODERATE RISK SEVERE; NEARBY  
TROPICAL EVENTS; HAZMAT OR OTHER LARGE EPISODES  
RED = FULL ENGAGEMENT FOR MODERATE TONIGHT RISK SVR  
AND/OR DIRECT TROPICAL THREATS; EVENTS OF NATIONAL  
SIGNIFICANCE  
 

 
   
PRELIMINARY POINT TEMPS/POPS
 
 
MCB 89 71 87 73 / 60 60 30 30  
BTR 89 74 87 75 / 60 60 30 40  
ASD 90 76 90 77 / 50 50 30 30  
MSY 90 79 89 79 / 50 50 30 30  
GPT 90 77 89 78 / 50 50 30 30  
PQL 91 76 91 77 / 50 50 20 30  
 

 
   
LIX WATCHES/WARNINGS/ADVISORIES
 
 
LA...NONE.  
GM...NONE.  
MS...NONE.  
GM...NONE.  

 
 

 
 
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