Area Forecast Discussion
Issued by NWS New Orleans/Baton Rouge, LA

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746
FXUS64 KLIX 301759 AAA
AFDLIX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
ISSUED BY NATIONAL WEATHER SERVICE BROWNSVILLE TX
100 PM CDT TUE SEP 30 2014

.AVIATION...VSBL SATL IMAGERY AND SURFACE OBS OVER SOUTHERN LA
INDICATES SOME DECENT FAIR WX CU FIELDS DEVELOPING OVER THE REGION.
THESE CLD DECKS WILL CONTINUE ON THROUGH MOST OF THE AFTERNOON AND
WILL THEN DISSIPATE SLOWLY WITH THE LOSS OF THE DAYTIME HEATING.
LATER TONIGHT FAIRLY LIGHT SURFACE WINDS WILL DEVELOP AFTER SUNSET.
THIS WILL COMBINE WITH GENERALLY CLEAR SKIES AND SURFACE DEWPOINTS
IN THE 70S TO ALLOW SOME AREAS OF FOG/LOW CEILINGS TO FORM AND
PERSIST THROUGH EARLY WED MORNING. EXPECT VFR/MVFR CONDITIONS TO
PREVAIL FOR MOST OF THE CURRENT TAF SET. HOWEVER THE LATE NIGHT FOG
AND LOW CEILINGS MAY BRIEFLY REDUCE CONDITIONS DOWN TO IFR/LIFR
LEVELS. ANY OF THESE THAT FORM WILL LIKELY BE PRETTY SHORT LIVED.
THE CEILINGS AND VSBYS WILL LIKELY QUICKLY IMPROVE AFTER SUNRISE.

.SHORT TERM...MDLS REALLY STRUGGLED WITH THE DEPTH AND SURGE OF DRY
AIR THAT OCCURRED YESTERDAY. 3-4 DAYS AGO THEY SUGGESTED WE WOULD
DRY OUT FOR MON AND TUE BUT THEN SAT NIGHT THEY BEGAN TO SUGGEST THE
BNDRY WOULD HOLD FURTHER NORTH AND MOISTURE WOULD NOT LEAVE THE
REGION ALONG WITH SCT SHRA MON AND TODAY. THIS WAS EVEN WITH WHAT
SHOULD BE A S/W RIDGE MOVING ACROSS THE AREA WHICH WOULD SUGGEST
SUBSIDENCE AND A BIG NEGATIVE ON RAIN CHANCES. WELL WE SHOULD HAVE
STUCK WITH OUR GUNS YESTERDAY AND KEPT THE FCST DRY BUT WILL DO SO
TODAY.

S/W RIDGING IS ALREADY MOVING INTO THE AREA AS THE L/W TROUGH SLOWLY
PUSHES EAST OVER THE CONTINENTAL DIVIDE TODAY. LAST NIGHT PWS JUST
OFF TO THE NORTH WERE NEAR 1.5 WHILE OUR BNDRY DRIFTED WELL INTO THE
GULF. COMBINE ALL THAT WITH WEAK NW FLOW ALOFT AND IT HELPED KEEP
THINGS QUIET YESTERDAY. AS FOR TODAY MOISTURE IS EXPECTED TO DROP
EVEN FURTHER ACROSS MUCH OF SELA AND SRN MS ALONG WITH THE RIDGE
MOVING THROUGH. THIS SHOULD MEAN ANOTHER DAY OF RELATIVELY QUIET
WEATHER AND ACTUALLY FEW CLOUDS IN THE SKY. ENJOY IT AS THIS VERY
WELL COULD BE THE LAST DRY DAY UNTIL THIS WEEKEND.

AS WE MOVE INTO TUE NIGHT AND MORE SO WED AND THU...MOISTURE WILL BE
BACK ON THE RISE AND OUR S/W RIDGE WILL FLATTEN OUT AND SHIFT TO THE
EAST. BY WED PWS SHOULD BE BACK AROUND 2 INCH WITH DEVELOPING WSW
FLOW ALOFT. THIS WILL LIKELY SEND A WEAK IMPULSE INTO THE REGION.
THIS COMBINED WITH THE INCREASE IN MOISTURE AND DAYTIME HEATING
SHOULD ALLOW FOR SCT CONVECTION WED.

THE L/W TROUGH MOVING ACROSS THE PLAINS WILL SHARPEN AND CONTINUE TO
SLIDE EAST. THIS WILL INCREASE THE SW FLOW ALOFT OVER THE REGION
WITH GREATER BROAD SCALE LIFT IN PLACE. BROAD DIVERGENCE ALOFT WILL
ALSO BE IN PLACE AND THIS ALONG WITH A RATHER MOIST AIRMASS SHOULD
LEAD TO SCT TO POSSIBLY NUMEROUS SHRA AND TSRA THU WITH CONVECTION
POSSIBLY INCREASING LATE THU/THU NIGHT AS OUR COLD FRONT BEGINS TO
APPROACH THE LOWER MS VALLEY. /CAB/

.LONG TERM...NOTHING HAS REALLY CHANGED IN THE EXTENDED PORTION OF
THE FCST. THE MEDIUM RANGE MDLS CONTINUE TO BE IN GREAT AGREEMENT
WITH THE PASSAGE OF OUR FIRST TRUE COLD FRONT. ONLY VERY MINOR
TIMING AND STRENGTH DIFFERENCES BUT OVERALL GOOD AGREEMENT. THEY ALL
CONTINUE TO TREND A TAD COOLER WITH THE ECMWF THE COLDEST. AGAIN
WILL USE A BLEND OF THE MDLS BUT WILL GIVE A LITTLE MORE WEIGHT TO
THE ECMWF GIVEN THE TRENDS.

FRI WILL BE THE LAST DAY THAT WE WILL SEE CONVECTION IN THE FCST. A
STRONG MID LVL JET DROPPING OUT OF WRN CANADA WILL SHARPEN THE L/W
TROUGH OVER THE CNTRL CONUS AND CAUSE IT TO DIG AS IT MOVES INTO THE
ERN CONUS FRI NIGHT WITH A CLOSED LOW LIKELY DEVELOPING OVER THE GRT
LAKES REGION. THIS WILL DRIVE A COLD FRONT THROUGH THE REGION FRI
AND WITH THE STRONG PUSH THIS FRONT COULD REACH THE COAST BY
MIDDAY/EARLY AFTN FRI. SHRA AND TSRA WILL BE LIKELY AHEAD AND WITH
THE FRONT WITH SOME LINGERING LIGHT SHRA IMMEDIATELY BEHIND THE
FRONT BUT DRY COLD AIR WILL QUICKLY PUSH IN FRI AFTN. AS FOR STRONG
SVR POTENTIAL...THERE WILL BE SOME INSTABILITY TO WORK WITH BUT MID
LVL FLOW WILL NOT BE THAT IMPRESSIVE. IN ADDITION MID LVL LAPSE
RATES ARE RATHER SHALLOW AND VT WILL ONLY BE AROUND 24-25C. CANT
RULE OUT A ROGUE STRONG/SVR STORM OR TWO BUT OVERALL NOT IMPRESSED
WITH THE SVR POTENTIAL WITH THIS SYSTEM.

HEADING INTO FRI NIGHT AND THIS WEEKEND LOOK FOR OUR FIRST REAL
TASTE OF AUTUMN. STRONG COLD AIR ADV OVERNIGHT FRI WILL OVERCOME ANY
MIXING FROM WINDS AND WILL COOL THINGS OFF IMPRESSIVELY WITH LOWS
SAT MORNING LIKELY RANGING FROM THE UPPER 50S IN SWRN MS TO MID 60S
ALONG THE COAST. IF THE FRONT IS ANY FASTER THEN LOWS COULD BE A FEW
DEGREES COOLER. THAT SAID LOOK FOR SUN MORNING TO BE THE COLDEST
MORNING SINCE MID MAY. DEWPOINTS ARE EXPECTED TO DROP INTO THE LOWER
40S IF NOT THE 30S ACROSS THE REGION AND SAT NIGHT OPTIMAL RAD
COOLING CONDITIONS COULD SET UP. THERE ARE SOME TIMING DIFFERENCES
B/T THE MDLS WITH RESPECT TO THE SFC HIGH BUT IT LOOKS LIKE IT WILL
SIT RIGHT OVER THE REGION THAT NIGHT PROVIDING RATHER LIGHT WINDS.
SKIES SHOULD BE CLEAR AND LL TEMPS WILL NOT BE WARMING YET AND ALL
OF THIS WOULD BE GREAT FOR RAD COOLING POTENTIAL. IF THE SFC HIGH
PUSHES EAST A TAD FASTER THAN WE MAY START TO SEE RETURN FLOW IN THE
LL WHICH COULD HURT LOWS BUT THE OTHER LIMITING FACTOR COULD BE
GROUND MOISTURE. IF WE OVERACHIEVE WITH THE RAINFALL ON FRI THEN
THERE COULD STILL BE ENOUGH MOISTURE TO HURT THE COOLING POTENTIAL.
AS MENTIONED EARLIER THE TREND FROM ALL OF THE MLDS HAS BEEN TO GO A
LITTLE COOLER WITH EACH MDL RUN AND SEE NO REASON TO DISAGREE WITH
THIS. THE ECMWF HAS BEEN THE MOST BULLISH AND ACTUALLY SHOWS MID 40S
IN SWRN MS. NOT GOING TO BITE ON THAT QUITE YET BUT WILL SHOW 50 FOR
MCB AND LOWER 50S ALONG AND NORTH OF THE 10/12 CORRIDOR. /CAB/

&&

.AVIATION...

MOSTLY LIGHT FOG WITH MVFR CONDITIONS IS EXPECTED TO DEVELOP AT A
HUM...MCB...BTR...ASD AND HDC...MAINLY BETWEEN 09-13Z. BRIEF OR
TEMPO IFR WILL BE POSSIBLE AT HUM AND MCB. CLOUD COVER SHOULD BE
LESS THAN MONDAY AND VFR CONDITIONS WILL PREVAIL AFTER 14Z THIS
MORNING THROUGH 06Z WEDNESDAY. ISOLATED SHRA THIS AFTERNOON MAY
BRIEFLY IMPACT HUM...NEW...MSY AND BTR...VERY ISOLATED SO WILL NOT
MENTION AT THIS TIME. 18

&&

.MARINE...

LIGHT EAST TO SOUTHEAST WILL PREVAIL...OCCASIONALLY VARIABLE THROUGH
THIS EVENING. ONSHORE FLOW WILL BEGIN TO DEVELOP LATE TONIGHT INTO
WEDNESDAY. THIS FLOW WILL INCREASE WEDNESDAY NIGHT INTO THURSDAY AS
THE PRESSURE GRADIENT INCREASES BETWEEN A DEPARTING HIGH OVER THE
EASTERN SEABOARD AND DEVELOPING LOW IN THE PLAINS. A STRONG COLD
FRONT WILL PUSH ACROSS THE COASTAL WATERS FRIDAY AND FRIDAY NIGHT.
1000 TO 700MB THICKNESS LAYER DECREASE ABOUT 60M TO 70M BEHIND THE
FRONT ACCORDING TO GFS AND EURO. GFS SHOWS WARM AIR ADVECTION AS THE
MAIN TROUGH MOVES TO THE EAST COAST SATURDAY AND SURFACE HIGH OVER
THE AREA. EURO HOLD COLD AIR ADVECTION LONGER INTO SATURDAY NIGHT.
LATER PACKAGES WILL EXAMINE THE DURATION OF OFF SHORE WINDS OVER THE
WEEKEND. ALL IN ALL...A SMALL CRAFT ADVISORY HEADLINES MAY BE NEEDED
FOR FRIDAY NIGHT INTO SATURDAY. 18

&&

.DECISION SUPPORT...
DSS CODE...GREEN.
DEPLOYED...NONE.
ACTIVATION...NONE.
ACTIVITIES...SLURRY SUPPORT.

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 TO HIGH RISK SVR
         AND/OR DIRECT TROPICAL THREATS; EVENTS OF NATIONAL
         SIGNIFICANCE.

&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  87  70  86  72 /  10  10  30  30
BTR  88  71  87  73 /  10  10  40  30
ASD  86  69  86  72 /  10  10  20  20
MSY  85  74  86  75 /  20  10  40  30
GPT  85  70  85  73 /  10  20  20  20
PQL  85  66  85  70 /  10  20  20  20

&&

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

$$

SHORT TERM...60
LONG TERM...63
GRAPHICAST/UPPER AIR...65







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