047  
FXUS64 KLIX 151335  
AFDLIX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE NEW ORLEANS LA  
735 AM CST FRI DEC 15 2017  
   
SOUNDING DISCUSSION
 
 
ROUTINE FLIGHT TERMINATED ABOUT 10 MILES EAST OF MOBILE AT A  
HEIGHT OF 110,000 FEET, OR 20.8 MILES ABOVE THE SURFACE.  
 
AIRMASS HAS MOISTENED SINCE LAST NIGHT WITH A PRECIPITABLE WATER  
VALUE OF 0.85 INCHES, BUT MOST OF THE MOISTURE IS LOCATED ABOVE  
700 MB, WITH A SATURATED OR NEARLY SATURATED LAYER BETWEEN 650 AND  
350 MB. THIS FITS WITH THE SOLID HIGH AND MID LEVEL CLOUD COVER  
OBSERVED AT LAUNCH. FRONTAL INVERSION LOOKED TO BE JUST BELOW 925  
MB AT LAUNCH TIME. FREEZING LEVEL THIS MORNING IS AT 9,600 FEET  
WITH THE -20C LEVEL AT 22,700 FEET.  
 
NORTHERLY WINDS AT THE SURFACE UP TO JUST BELOW 925 MB, WITH  
WESTERLY WINDS FOR THE REMAINDER OF THE FLIGHT. MAX WIND OF 121  
KNOTS WAS REPORTED NEAR 34,000 FEET. 35  
 

 
   
PREV DISCUSSION
 
/ISSUED 357 AM CST FRI DEC 15 2017/  
 
SHORT TERM...  
AN UPPER TROUGH WILL BE SWINGING ACROSS THE MISSISSIPPI VALLEY  
THIS MORNING. AT THE SURFACE, OBSERVATIONS SHOW A COLD FRONT  
CURRENTLY MOVING SOUTHWARD ACROSS THE CWA. AT THE SAME TIME, THE  
SUB-TROPICAL JET IS CARRYING PACIFIC MOISTURE ACROSS MEXICO TO THE  
NORTHERN GULF COAST. SHOWERS WILL DEVELOP OVER PORTIONS OF THE  
FORECAST AREA AS A RESULT OF THIS OVERRUNNING MOISTURE. THE BULK  
OF RAIN WILL BE LIMITED TO AREAS FROM NEW ORLEANS SOUTHWARD.  
EXACTLY HOW FAR NORTH THE SHOWERS ACTUALLY REACH IS QUITE  
CHALLENGING. THINKING IT WILL BE AROUND I-12. IN TERMS OF  
TEMPERATURES, THE COMBINATION OF OVERCAST SKIES AND COLD AIR  
ADVECTION WILL LIKELY KEEP TEMPS FAIRLY STEADY THROUGHOUT THE DAY.  
 
THESE SHOWERS WILL FADE AND SHIFT SOUTH AS THE FRONT CONTINUES  
TOWARDS THE CENTRAL GULF OF MEXICO. DECREASING CLOUDS AND COLDER DRY  
AIR MASS MOVING IN WILL BRING DOWN NIGHTTIME LOWS QUITE A BIT.  
EXPECTING MID 30S FOR MOST LOCATIONS WITH A FEW IN MISSISSIPPI  
TOUCHING THE FREEZING MARK SATURDAY MORNING.  
 
LONG TERM...  
MODELS STILL SHOW A CUTOFF LOW THAT IS CURRENTLY STUCK OVER THE BAJA  
OF CALIFORNIA GETTING PICKUP BY A PACIFIC TROUGH AND RACING  
NORTHEAST TO THE MID MISSISSIPPI VALLEY THIS WEEKEND. IN RESPONSE  
TO THIS, A SURFACE LOW AND APPENDANT FRONTAL BOUNDARY WILL  
DEVELOP OVER EAST TEXAS, WITH THE FRONT STALLING OVER THE CWA  
SUNDAY. NUMEROUS SHOWERS AND A FEW THUNDERSTORMS ARE LIKELY TO  
DEVELOP AS FRONTOGENESIS TAKES PLACE. WHILE RAIN WILL BEGIN FROM  
WEST TO EAST SATURDAY NIGHT, MOST OF THE HIGHER POPS SHOULDN'T  
COME IN UNTIL SUNDAY.  
 
THE BOUNDARY WILL LIKELY REMAIN STALLED ALONG THE NORTHERN GULF  
COAST THROUGH TUESDAY AS TROUGHING IS MAINTAINED WEST OF THE CWA.  
THIS WILL LEAD TO BOUTS OF RAIN MOVING ACROSS THE AREA RATHER THAN  
CONSTANT DOWNPOURS. CONFIDENCE IN THE FORECAST IS NORMAL THROUGH  
THIS PERIOD AND BELOW NORMAL THEREAFTER. THE MAIN DIFFERENCE IS THE  
THE GFS CLEARS OUT MOISTURE WED AND THU WITH THE AFOREMENTIONED  
PACIFIC TROUGH, WHILE THE ECMWF IS SLOWER WITH THE PROGRESSION OF  
THIS TROUGH. DIDN'T MAKE TOO MANY CHANGES FROM PREVIOUS FORECAST  
AND WENT WITH A BLEND OF SOLUTIONS FOR POPS.  
 
MEFFER  
 
AVIATION...VFR CONDITIONS WILL GENERALLY PREVAIL THROUGH THE TAF  
FORECAST PERIOD WITH PRIMARILY MID AND HIGH LEVEL CLOUDS EXPECTED. A  
COLD FRONT WILL PUSH SOUTH ACROSS THE FORECAST AREA OVERNIGHT/EARLY  
FRIDAY MORNING. SOME PATCHY FOG MAY OCCUR PRIOR TO THE FRONTAL  
PASSAGE AT KGPT AND KHUM. OTHERWISE, A FEW SHOWERS MAY IMPACT THE  
MORE COASTAL LOUISIANA TAF SITES FRIDAY MORNING. 11  
 
MARINE...COLD FRONT QUICKLY MOVING THROUGH AND WINDS WILL PICK UP  
LATER THIS MORNING. WINDS OVER ALL OF THE OPEN WATERS WILL INCREASE  
TO AT LEAST 15-20 KTS BUT THE OUTER WATERS SOUTH AND WEST OF THE  
DELTA WILL LIKELY BE CLOSER TO 20 KTS WITH HIGHER GUSTS. WITH THAT  
WILL HOIST AN SCY FOR THOSE WATERS AND THEN AN SCS FOR THE REST OF  
THE OPEN WATERS JUST FOR TODAY. HIGH PRESSURE WILL QUICKLY SLIDE  
TOWARDS THE SOUTHEASTERN CONUS AND WINDS WILL RELAX SOME FRIDAY  
NIGHT AND BEGIN TO SHIFT OUT OF THE EAST THROUGH SATURDAY. BY  
SATURDAY EVENING AND INTO SUNDAY WITH HIGH PRESSURE STILL OFF TO THE  
EAST AND LOWER PRESSURE DEVELOPING ALONG THE TX COAST WINDS WILL  
BEGIN TO SLOWLY INCREASE AND BECOME ONSHORE. AS THE LOW PULLS AWAY  
TO THE NORTHEAST THE FRONT WILL BECOME STATIONARY OVER THE AREA WITH  
WINDS RELAXING AGAIN. /CAB/  
   
DECISION SUPPORT
 
 
DSS CODE: BLUE.  
DEPLOYED: NONE.  
ACTIVATION: NONE.  
ACTIVITIES: SMALL CRAFT ADVISORY  
 
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 49 31 55 49 / 10 0 10 20  
BTR 50 35 57 53 / 20 0 10 20  
ASD 52 35 57 53 / 40 10 10 20  
MSY 53 40 58 55 / 60 10 10 20  
GPT 52 37 56 54 / 30 10 10 20  
PQL 52 31 57 51 / 20 10 10 10  
 

 
   
LIX WATCHES/WARNINGS/ADVISORIES
 
 
LA...NONE.  
GM...SMALL CRAFT ADVISORY UNTIL 6 PM CST THIS EVENING FOR GMZ570-572-  
575.  
 
MS...NONE.  
GM...SMALL CRAFT ADVISORY UNTIL 6 PM CST THIS EVENING FOR GMZ572-575.  
 

 
 

 
 
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