951  
FXUS64 KLIX 231427  
AFDLIX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE NEW ORLEANS LA  
827 AM CST FRI FEB 23 2018  
   
SOUNDING DISCUSSION
 
 
SOME MOISTENING EVIDENT IN THIS MORNING'S SOUNDING. PRECIPITABLE  
WATER HAS COME UP TO 1.29 INCHES, WHICH IS ACTUALLY WELL ABOVE  
NORMAL FOR THIS TIME OF YEAR AND JUST BELOW THE 90TH PERCENTILE  
OF OBSERVED VALUES ON THIS DATE. THAT BEING SAID, A COUPLE STORMS  
COULD BE ACCOMPANIED BY FAIRLY EFFICIENT RAINFALL. THE GOOD NEWS  
IS THAT THE MEAN WIND IS IN THE CLOUD LAYER IS 15 TO 20 KTS, SO  
STORMS SHOULDN'T REMAIN IN ONE PLACE FOR VERY LONG. NOT A  
FAVORABLE SOUNDING FOR BACKBUILDING STORMS, EITHER, SO ONLY REAL  
CONCERN FOR HEAVY RAINFALL WOULD BE IF MULTIPLE STORMS HAPPEN TO  
LINE UP IN SUCH A WAY THAT THEY'D MOVE OVER THE SAME AREA IN  
RELATIVELY QUICK SUCCESSION. OTHERWISE, THERE SHOULD BE ENOUGH  
TIME BETWEEN STORMS FOR ANY PONDING TO DRAIN. CAN'T RULE OUT ONE  
OR TWO STRONG STORMS, BUT SEVERE WEATHER LOOKS UNLIKELY.  
 

 
   
PREV DISCUSSION
 
/ISSUED 417 AM CST FRI FEB 23 2018/  
 
SHORT TERM...  
AN UPPER LEVEL RIDGE IS CURRENTLY CENTERED NORTH OF THE BAHAMAS AND  
EXTENDS INTO THE BAY OF CAMPECHE WHILE A TROUGH AXIS IS LOCATED WEST  
OF THE ROCKY MOUNTAINS. MOISTURE WRAPPING AROUND THE AREA OF HIGH  
PRESSURE WILL SURGE NORTHWARD ACROSS THE CWA TODAY. DAYTIME HEATING  
WITH CONTINUED UNUSUALLY HIGH TEMPERATURES FOR THIS TIME OF YEAR  
WILL ENHANCE SHOWER AND THUNDERSTORM DEVELOPMENT THIS AFTERNOON. ALL  
MODELS INCLUDING MESO AND MEDIUM RANGE GLOBAL MODELS SUGGEST POP  
COVERAGE OVER 50% FOR MOST PORTIONS OF THE FORECAST AREA. THEY ALL  
SEEM TO CONVERGE ON NORTHWESTERN ZONES AS THE AREA THAT WILL HAVE  
THE HIGHEST CONCENTRATION OF CONVECTION, THUS ORIENTED POPS THAT  
WAY. ACTIVITY WILL DECREASE DURING THE OVERNIGHT PERIOD, BUT NOT  
COMPLETELY DIMINISH. OVERCAST SKIES WILL BOTH KEEP TEMPS FROM  
FALLING MUCH BELOW 70 (20+ DEGREES ABOVE NORMAL!) AND LIMIT FOG  
DEVELOPMENT TO JUST A LIGHT HAZE.  
 
LONG TERM...  
THE MAIN UPPER TROUGH AXIS CURRENTLY WEST OF THE ROCKIES WILL  
FINALLY LIFT NORTHEAST AND RACE ACROSS THE MIDSECTION OF THE COUNTRY  
THIS WEEKEND. THIS WILL SEND A FRONT THROUGH THE FORECAST AREA EARLY  
SUNDAY MORNING. MODEL SOUNDINGS SHOW STEEPER LAPSE RATES IN THE MID  
LEVELS, EQUATING TO MUCAPE VALUES INTO THE 500-1000J/KG RANGE. DUE  
TO 500MB WINDS WELL OVER 50 KNOTS, 0-6KM SHEAR TOUCHES 50KTS. THOSE  
NUMBERS ARE SUFFICIENT TO SUPPORT MARGINALLY SEVERE THUNDERSTORMS.  
WBZ STILL ABOVE 11KFT SUGGESTS HAIL WILL BE A MINIMAL THREAT WHILE  
UNIDIRECTIONAL WINDS SAYS DOWNDRAFT WINDS ARE THE GREATEST THREAT.  
THE CHANCE FOR ANYTHING SEVERE WILL DIMINISH RAPIDLY AFTER THE  
BOUNDARY MOVES IN. IT STILL APPEARS THAT THE BOUNDARY WILL STALL  
SOMEWHERE BETWEEN BATON ROUGE AND BOOTHVILLE. MONDAY'S RAIN CHANCES  
WILL DEPEND ON IF THE FRONT GETS NUDGED OFFSHORE OR STAYS PUT. THIS  
SET OF MODEL RUNS, THEY SUGGESTS AN OFFSHORE JOG WHICH WILL LEAD TO  
DRY FORECAST FOR THOSE NORTH OF NEW ORLEANS (FOR THE MOST PART) AND  
WET FROM THERE SOUTHWARD.  
 
THE RIDGE THAT WAS NORTH OF THE BAHAMAS WILL BE SETTLING IN OVER THE  
SOUTHERN GULF OF MEXICO THROUGH THE REST OF NEXT WEEK. THIS MAY OR  
MAY NOT PUT THE CWA IN CONDUCIVE AREA FOR PERSISTENT SHOWER AND  
THUNDERSTORM DEVELOPMENT EARLY NEXT WEEK. IT WILL BE DEPENDENT ON  
HOW CLOSE THE CENTER IS IN PROXIMITY TO THE CWA. ATTM, MODELS SHOW A  
SHORTWAVE PASSING FROM SW TO NE ACROSS LOUISIANA TUESDAY. SHOWERS  
AND STORMS WILL ACCOMPANY THIS WAVE. POPS SHOULD HAVE A GRADIENT  
WITH HIGHER CHANCES IN NORTHWESTERN ZONES AND LOWER IN SOUTHEASTERN  
ONES. PROGRESSIVE PATTERN BRINGS A MORE ESTABLISHED TROUGH ACROSS  
THE MIDDLE OF THE COUNTRY MIDWEEK. IF THE RIDGE TO THE SOUTH STAYS  
IN PLACE, STORMS COMING IN WILL LIKELY BE WEAKENING IN INTENSITY AND  
LOWERING IN OVERALL COVERAGE AS THEY MOVE FROM NORTH TO SOUTH ACROSS  
THE CWA.  
 
MEFFER  
 
AVIATION...MVFR TO OCCASIONAL IFR CATEGORY CONDITIONS WILL PREVAIL  
OVERNIGHT AND FRIDAY MORNING...PRIMARILY AS A RESULT OF CEILINGS,  
BUT ALSO DUE TO RESTRICTED VSBYS DUE TO PATCHY FOG IN SOME  
LOCATIONS. VFR TO MVFR CONDITIONS WILL THEN PREVAIL DURING THE  
AFTERNOON HOURS FRIDAY OUTSIDE OF SCATTERED CONVECTION. CEILINGS  
WILL LOWER AGAIN INTO THE MVFR TO IFR CATEGORIES FRIDAY NIGHT. /11/  
 
MARINE...LITTLE CHANGE IN THE FORECAST WITH MODERATE ONSHORE FLOW  
TO CONTINUE INTO THE WEEKEND. THE COLD FRONT WILL FINALLY MAKE ITS  
WAY TO THE COAST SUNDAY BEFORE STALLING FOR ABOUT 18-24 HOURS AND  
THEN GET A SECONDARY SURGE SUNDAY EVENING. THE FRONT WILL PUSH SOUTH  
OF THE COAST MOMENTARILY LEADING WINDS TO VEER AROUND TO OFFSHORE  
THROUGH THE DAY MONDAY. THE FRONT WILL THEN QUICKLY RETREAT BACK TO  
THE NORTH EARLY TUESDAY WITH RETURN FLOW BACK IN PLACE MIDDAY. /CAB/  
 
DECISION SUPPORT...  
DSS CODE: GREEN.  
DEPLOYED: NONE.  
ACTIVATION: NONE.  
ACTIVITIES: NONE.  
 
DECISION SUPPORT SERVICES (DSS) CODE LEGEND  
GREEN = NO WEATHER IMPACTS THAT REQUIRE ACTION.  
BLUE = LONG-FUSED WATCH, WARNING, OR ADVISORY IN EFFECT OR  
HIGH VISIBILITY EVENT.  
YELLOW = HEIGHTENED IMPACTS WITH SHORT-FUSED WATCH, WARNING OR  
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 RISK OF SEVERE AND/OR  
DIRECT TROPICAL THREATS; EVENTS OF NATIONAL SIGNIFICANCE.  
 

 
   
PRELIMINARY POINT TEMPS/POPS
 
 
MCB 82 69 83 63 / 70 40 50 80  
BTR 84 69 84 64 / 80 20 30 70  
ASD 84 69 84 69 / 60 40 30 40  
MSY 82 70 84 68 / 60 30 20 40  
GPT 79 68 79 68 / 50 50 20 40  
PQL 80 67 81 68 / 50 40 20 40  
 

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

 
 

 
 
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