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

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238
FXUS64 KLIX 141636
AFDLIX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
1136 AM CDT SUN SEP 14 2014

.AVIATION...
IFR-MVFR CLOUD DECK SLOWLY ERODED AND MOVING WEST FROM KBTR TO
WEST OF KMCB AT THIS TIME. VFR CONDITIONS ARE EXPECTED TO PREVAIL
OR IMPROVE TO PREVAILING THIS AFTERNOON ALL TERMINALS. CONVECTION
SHOULD BE LIMITED IN COVERAGE AND WILL BE OMITTED FROM TAFS. 24/RR

&&

.SOUNDING DISCUSSION...
STABLE LOOKING SOUNDING WITH FRONTAL INVERSION NOTED FROM SURFACE
TO 2KFT. COLUMN HAS DRIED CONSIDERABLY WITH PRECIPITABLE WATER
VALUES LOWERED TO 1.86 INCHES. WINDS WERE NE-N 10-15KT SURACE TO
7500 FT...NE-NW 5-15 KT ABOVE WITH A SMALL LAYER OF VARIABLE WINDS
BETWEEN 30-33KFT. 24/RR

&&

.PREV DISCUSSION... /ISSUED 354 AM CDT SUN SEP 14 2014/

SHORT TERM...QUIET NIGHT WITH NO CONVECTION OVER LAND AREAS WITH
THE EXCEPTION OF EXTREME COASTAL PLAQUEMINES PARISH AROUND THE MOUTH
OF THE RIVER. COLD FRONT MADE IT ALL THE WAY TO THE LA COAST AND
INTO THE COASTAL WATERS SOUTH OF MS. DRIER AIR IS NOTED OVER THE
REGION WITH DEWPOINTS AS LOW AS THE MID 60S ACROSS SWRN MS. AT 8Z
TEMPS WERE RANGING FROM THE MID 60S TO MID 70S.

TODAY MAIN QUESTION IS HOW MUCH CONVECTION WE SEE TODAY AND HOW FAR
INLAND IT GETS. THE SECOND QUESTION APPEARS TO BE AN EASIER ANSWER
AS THE LOCATION THAT HAS THE BEST CHANCE FOR MEASURABLE RAIN SHOULD
BE SE OF A LINE FROM HOUMA TO POPLARVILLE. EVEN THOUGH THE COLD
FRONT IS FURTHER SOUTH THAN THAT LINE ABUNDANT MOISTURE IS IN PLACE
JUST ABV THE SFC AND THERE WILL BE AN AREA OF LL CONVERGENCE NOTED
AROUND THAT PREVIOUSLY MENTIONED LINE. THIS IS ALSO CO-LOCATED WITH
THE H85 THETA E RIDGE. IF THERE ARE ENOUGH BREAKS IN THE CLOUDS TO
ALLOW FOR A LITTLE DIURNAL HEATING THEN WE SHOULD SEE A LINE OF
CONVECTION SOMEWHERE ACROSS SELA AND COASTAL MS. IF CLOUDS HOLD
STRONG FOR THE MOST PART THEN ISLTD CONVECTION AT BEST IS EXPECTED.
HAVE DECIDED TO GO WITH 30-40% POPS ANTICIPATING JUST ENOUGH HEATING
FOR SCT STORMS BUT DEFINITELY NOT THE HEAVY RAIN POTENTIAL THAT
COULDVE DEVELOPED HAD THE FRONT STALLED A TAD FARTHER NORTH AND OUR
TROPICAL WAVE MOVED ACROSS THE NRN GULF.

MON AND TUE RAIN CHANCES SHOULD BE FAR GREATER. MON THE FRONT WILL
BEGIN TO LOSE MUCH OF ITS IDENTITY BUT BROAD LL CONVERGENCE WILL BE
NOTED OVER MOST OF THE REGION ALONG WITH THE RRQ OF A WEAK JET
STREAK. THE BIGGEST FCST IMPACT APPEARS TO BE DEEP TROPICAL MOISTURE
SURGING NORTH OUT OF THE GULF...H85 THETA E AIR OF AROUND 340-345K
AND PWS RAMPING BACK UP TO NEAR 2"(ABOUT 130-140% OF NORMAL). THIS
ALONG WITH THE WEAKENING MID LVL RIDGE SHOULD ALLOW FOR SCT TO EVEN
NUM STORMS DURING THE AFTN WITH MORE RAIN IN STORE FOR TUE. A SECOND
COLD FRONT WILL BE ON THE WAY. MON NIGHT A S/W WILL BE DROPPING
THROUGH THE UPPER MS VALLEY AND INTO THE OH VALLEY. THIS WILL HELP
TO DEEPEN THE ERN CONUS L/W TROUGH WHICH IN HAND WILL DRIVE A COLD
FRONT TWRDS THE LOWER MS VALLEY LATE TUE. AHEAD OF THIS FRONT
MOISTURE WILL CONTINUE TO POOL BUT BIGGEST CHANGE WILL BE BROAD LIFT
ACROSS THE REGION AS MID LVL HGHTS FALL AND COOL IN RESPONSE TO THE
DEVELOPING L/W TROUGH. THIS SHOULD LEAD TO SCT TO NUM STORMS ONCE
AGAIN. AS FOR TEMPS LOOK FOR NEAR NORMAL BUT IF CONVECTION STARTS
EARLY AFTN HIGHS COULD REMAIN A TAD BELOW NORMAL THX TO CLOUDS AND
RAIN. /CAB/

LONG TERM...MEDIUM RANGE MDLS IN AGREEMENT THROUGH MUCH OF THE WORK
WEEK WITH THE L/W TROUGH AXIS SLIDING EAST AND A RIDGE BUILDING OVER
TX BUT OVER THE WEEKEND THE GFS AND ECMWF DIVERGE AS THE ECMWF IS
MUCH DEEPER WITH THE NEXT TROUGH TRYING TO RE-ESTABLISH THE ERN
CONUS L/W TROUGH. THE GFS IS NO AS DEEP WITH IT AND THUS HOLDS ONTO
A RIDGE OVER MUCH OF THE GULF COAST STATES. GIVEN THE LAST YEAR WILL
BASE THE FCST CLOSER TO THE ECMWF AS THE ERN CONUS TROUGH HAS WON
OUT MORE OFTEN THAN NOT. SO WHAT DOES THIS MEAN FIRST...THE COLD
FRONT SHOULD MOVE INTO THE REGION EARLY WED AND THEN CONTINUE TO
SLOWLY WORK INTO THE GULF. BY THU WE SHOULD SEE SLIGHTLY COOLER
TEMPS AND DRIER CONDITIONS WITH LITTLE IF ANY RAIN THU AND FRI. BY
FRI NIGHT AND ESPECIALLY INTO THE WEEKEND RETURN FLOW WILL SET UP
WITH MOISTURE RETURNING AND THUS CONVECTION SLOWLY RETURNING ACROSS
THE REGION. /CAB/

AVIATION...EXPECT MVFR TO VFR CONDITIONS THIS MORNING AS A FRONTAL
PASSAGE WILL KEEP WINDS OUT OF THE NORTHEAST TODAY. MVFR DECK SHOULD
RISE TO VFR DECK AFTER SUNRISE AND SHOULD REMAIN THERE THROUGHOUT
THE DAY. CONVECTION TODAY SHOULD BE LIMITED AND HAVE ONLY INCLUDED
VCTS FOR THE MORE COASTAL SITES FOR TODAY. WILL HAVE TO WATCH FOR
DEVELOPMENT FOR AMENDMENTS THIS AFTERNOON. 13/MH

MARINE...FRONT WILL LINGER NEAR THE COAST TODAY AND TOMORROW BEFORE
LOSING ITS IDENTITY MON NIGHT.  HIGH PRESSURE CNTRD WELL OFF TO THE
NE AND LOWER PRESSURE OVER THE WRN GULF WILL MAINTAIN MOSTLY ERLY
WINDS AT 10 TO 15 KNOTS THROUGH SUN NIGHT. STARTING MON...A
LIGHTER WIND REGIME IS EXPECTED THROUGH AT LEAST THE MIDDLE OF
NEXT WEEK AS WEAKER HIGH PRESSURE DEVELOPS CLOSER TO THE MARINE
AREA. /CAB/


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  86  70  90  71 /  10  20  60  30
BTR  87  73  91  74 /  20  20  60  30
ASD  87  75  89  74 /  40  30  60  40
MSY  87  77  90  76 /  40  30  60  40
GPT  87  76  89  75 /  30  30  60  40
PQL  88  74  89  73 /  30  30  60  40

&&

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

$$








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