206  
FXUS64 KLIX 261326  
AFDLIX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE NEW ORLEANS LA  
826 AM CDT WED APR 26 2017  
   
..SOUNDING DISCUSSION
 
 
THE SOUNDING THIS MORNING DEPICTS THE RETURN OF MOISTURE AND THE  
GULF AIRMASS DUE TO SOUTHERLY ONSHORE FLOW, THOUGH IT IS SHALLOW.  
A STRONG 17 F TEMPERATURE INVERSION IS AT 900 MB AND MARKS A MUCH  
DRIER AIRMASS STILL ABOVE. WINDS ABOVE THE INVERSION BECOME  
WESTERLY. PW IS BELOW AVERAGE AT 0.74 INCHES. THE STRONG INVERSION  
AND DRY AIR JUST ABOVE THE BOUNDARY LAYER SHOULD KEEP THE AREA  
NEARLY RAIN FREE THROUGH THE DAY AND INTO THE EARLY EVENING  
HOURS.  
 
KRAUTMANN  
 

 
 
   
PREV DISCUSSION
 
/ISSUED 347 AM CDT WED APR 26 2017/  
 
SHORT TERM...  
A BROAD UPPER LEVEL TROUGH IS DIGGING SOUTHEAST ACROSS THE SOUTHERN  
ROCKIES AND BEGINNING TO SHARPEN. IT WILL QUICKLY MOVE INTO AND  
THROUGH THE CENTRAL PLAINS THROUGHOUT THE DAY. MODELS ARE IN GOOD  
AGREEMENT THAT THE TROUGH WILL THEN LIFT NORTHEAST TOWARDS THE GREAT  
LAKES THIS EVENING AND TONIGHT. A FRONTAL BOUNDARY ASSOCIATED WITH  
THE UPPER TROUGH WILL BE THE FOCUS FOR SHOWER AND THUNDERSTORM  
ACTIVITY THAT MOVES THROUGH THE CWA. CONVECTION SHOULD BE ON THE  
NORTHWESTERN DOORSTEP OF THE FORECAST AREA THURSDAY AT 00Z AND  
EXITING EASTERN AREAS AROUND SUNRISE THURSDAY. THE TYPICAL POP  
COVERAGE IN SIMILAR WEATHER PATTERNS IS MORE AND STRONGER STORMS  
ALONG THE LA/MS BORDER AND MINIMAL ALONG THE LA COAST(EXAMPLE: THE  
LAST SYSTEM THAT JUST MOVED THROUGH). THE CURRENT POP FORECAST IS  
BASED ON THAT SCENARIO WITH 80% IN SOUTHWEST MISSISSIPPI AND 20% IN  
SOUTHERN PLAQUEMINES PARISH. THE THREAT FOR SEVERE WEATHER WILL BE  
IN A SIMILAR WITH THE BEST PROBABILITIES NORTH OF I-12 AND MINIMAL  
THREAT ON THE COAST. MODEL SOUNDINGS SHOW THIS AS WELL WITH A MID  
LEVEL WARM NOSE THAT DOESN'T ERODE AND MUCH WEAKER WINDS IN THE  
COLUMN AT POINTS FURTHER SOUTH THAN NORTH. ML CAPE VALUES OVER  
2000J/KG, LI'S -6 TO -8 COMBINED WITH SHEAR OVER 40 KNOTS WILL BE  
SUFFICIENT FOR SEVERE THUNDERSTORMS IN THOSE NORTHERN AREAS. CURRENT  
SPC DAY 1 SHOWS SLIGHT RISK NORTHWEST OF OF A BTR TO MCB LINE AND  
MARGINAL FOR POINTS SOUTH OF THERE. IN ADDITION, THE INTENSITY OF  
STORMS SHOULD BE ON A DOWNWARD TREND AS THEY PROGRESS THROUGH THE  
EASTERN HALF OF THE CWA EARLY TOMORROW MORNING. THIS MAKES SENSE  
WITH THE TROUGH LIFTING FURTHER AWAY, AND TAKING THE STRONGER WIND  
FIELD WITH IT.  
 
LONG TERM...  
POST FRONTAL UPPER LEVEL RIDGE WILL BE EXPANDING OVER THE  
SOUTHEASTERN UNITED STATES ON FRIDAY. TEMPERATURES WILL RESPOND BY  
MODERATING WELL INTO THE 80S FOR THE AFTERNOON HIGHS. MOISTURE WILL  
BEGIN TO SURGE IN AS WELL AS SOUTHEAST FLOW STRENGTHENS. LOW TO MID  
70 DEGREE DEWPOINTS WILL ENGULF THE CWA BY THE AFTERNOON.  
 
THE SECOND AND LIKELY MORE IMPACTFUL EVENT OF THIS FORECAST PERIOD  
WILL BE ROLLING THROUGH DURING THE SECOND HALF OF THIS WEEKEND. AN  
UPPER TROUGH WILL BE CLOSING A LOW AND ROTATING NEGATIVE AS IT DIGS  
WELL INTO TEXAS AND THE LOWER MISSISSIPPI VALLEY SATURDAY INTO  
SUNDAY. A WIDE SWATH OF SHOWERS AND EMBEDDED STRONG/SEVERE  
THUNDERSTORMS WILL MARCH ACROSS THE STATE ON SUNDAY. SURFACE WINDS  
LOOK TO BE STRONG SATURDAY AND SATURDAY NIGHT AS A SUB-1000MB  
SURFACE LOW DEVELOPS OVER TEXAS. THIS WILL CONTINUE TO BRING  
INCREASED MOISTURE WELL PAST THE CWA. CAPE VALUES WILL LIKELY BE  
OVER 2000 J/KG AS MOISTURE AND TEMPS STAY HIGH WHILE MID LEVEL TEMPS  
DROP FROM THE APPROACHING DEEP TROUGH. THAT TYPE OF MOISTURE AND  
INSTABILITY COMBINED WITH A 50+KT MID LEVEL JET MAY SET THE STAGE  
FOR QUITE A BIT SEVERE WEATHER AND MAYBE A FEW SIGNIFICANTLY STRONG  
CELLS. ALL MODES OF SEVERE WEATHER POSSIBLE ALTHOUGH TORNADOES AND  
WIND SEEM TO BE THE MORE LIKELY THREATS. TIMING IS THE BIGGEST ??  
ATTM AS NOW THE ECMWF IS SLOWER THAN THE GFS. WILL LIKELY SEE  
FLUCTUATIONS UNTIL THE EVENT OCCURS.  
 
DRY AND COOLER TEMPS EXPECTED EARLY NEXT WEEK AS POST FRONTAL  
SURFACE HIGH PRESSURE BUILDS IN. A PROGRESSIVE UPPER LEVEL PATTERN  
IN GENERAL WILL LIKELY BRING THE THREAT FOR RAIN BACK INTO THE  
FORECAST FAIRLY QUICKLY.  
 
MEFFER  
 
AVIATION...  
SCT-BKN015 WILL MOVE INTO EACH TERMINAL TODAY. THIS WILL BECOME AN  
OVC035 BY EARLY EVENING. WINDS WILL BECOME GUSTY FROM THE SOUTH  
TODAY AS SOUTH WINDS OF 15 TO 20 KNOTS WITH HIGHER GUSTS ARE  
EXPECTED. SOME LOW LEVEL OVC005 CEILINGS MAY OCCUR OVERNIGHT AS THE  
SH/TS BEGIN TO MOVE IN AS WELL.  
 
MARINE...  
AN INCREASING PRESSURE GRADIENT OVER THE COASTAL WATERS RELATED TO A  
DEEPENING LOW PRESSURE SYSTEM IN THE SOUTHERN PLAINS WILL RESULT IN  
EXERCISE CAUTION CONDITIONS OVER ALL WATERS THROUGH 4PM TODAY. AS  
WINDS RISE IN ADVANCE OF THE FRONT, ADVISORY CONDITIONS WILL START  
AT 4PM AND LAST THROUGH AT LEAST 4AM THURSDAY. WINDS ON THE BACK  
SIDE OF THIS FRONT ARE EXPECTED TO COLLAPSE RAPIDLY AND ALL FLAGS  
SHOULD BE ABLE TO LOWER AFTER 9Z THURSDAY. AS A COLD FRONT STALLS  
OVER THE NORTHERN GULF TONIGHT AND THURSDAY, WINDS WILL REMAIN  
RATHER WEAK UNTIL THURSDAY NIGHT AS FLOW WILL BECOME ESTABLISHED  
ONCE AGAIN OUT OF THE SOUTH AHEAD OF THE NEXT MUCH STRONGER COLD  
FRONT EXPECTED TO MOVE THROUGH SUNDAY NIGHT IN TO MONDAY MORNING.  
WINDS WILL RISE ENOUGH TO BECOME HIGH END ADVISORY CONDITIONS BUT  
MAY ACTUALLY BECOME STRONG ENOUGH FOR GALE CONDITIONS OR AT LEAST  
GUSTS TO GALE FORCE BY AS EARLY AS SATURDAY NIGHT. AS THE FRONT  
MOVES THROUGH MONDAY MORNING, WINDS WILL SHIFT TO NORTHWEST AND  
REMAIN AT AROUND 20-25KT EARLY THURSDAY. WINDS WILL EASE THROUGH THE  
MORNING WITH ALL FLAGS POSSIBLY DROPPING BY NOON OR SHORTLY  
AFTER.  
 
DECISION SUPPORT...  
DSS CODE...GREEN.  
DEPLOYED...NONE.  
ACTIVATION...NONE.  
ACTIVITIES...NONE.  
 
DECISION SUPPORT SERVICE (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 OF SEVERE WEATHER;  
NEARBY TROPICAL EVENTS, HAZMAT OR OTHER LARGE EPISODES  
RED = FULL ENGAGEMENT FOR MODERATE RISK OF SEVERE WEATHER; DIRECT  
TROPICAL THREATS; EVENTS OF NATIONAL SIGNIFICANCE.  
 

 
   
PRELIMINARY POINT TEMPS/POPS
 
 
MCB 85 55 83 65 / 10 80 0 10  
BTR 87 58 84 67 / 10 70 0 10  
ASD 84 63 85 71 / 0 70 10 10  
MSY 85 63 84 72 / 0 60 10 10  
GPT 78 66 83 74 / 0 70 20 10  
PQL 77 65 84 69 / 0 70 30 10  
 

 
   
LIX WATCHES/WARNINGS/ADVISORIES
 
 
LA...NONE.  
GM...SMALL CRAFT ADVISORY FROM 4 PM THIS AFTERNOON TO 4 AM CDT  
THURSDAY FOR GMZ532-536-538-550-552-555-557-570-572-575-577.  
 
MS...NONE.  
GM...SMALL CRAFT ADVISORY FROM 4 PM THIS AFTERNOON TO 4 AM CDT  
THURSDAY FOR GMZ536-538-550-552-555-557-570-572-575-577.  
 

 
 

 
 
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