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

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065
FXUS64 KLIX 220909
AFDLIX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
409 AM CDT MON SEP 22 2014

.SYNOPSIS...

COLD FRONT AT 3 AM APPEARS TO HAVE JUST CLEARED INTERSTATE 20 AND
CONTINUING TO MOVE SOUTHWARD. ISOLATED CONVECTION IS JUST TO THE
NORTH OF THE FRONT. EVEN AHEAD OF THE FRONT...THE AIR IS
RELATIVELY DRY WITH DEW POINTS ACROSS MOST OF THE AREA IN THE MID
60S...AND PRECIPITABLE WATER VALUES AROUND 1.2 INCHES. SOUNDER
DATA SHOWS A RIBBON OF AROUND 1.6 INCHES NEAR THE FRONT.

&&

.SHORT TERM...

ONLY PRECIPITATION EVENT DURING THE SHORT TERM PORTION OF THE
FORECAST OVER LAND AREAS WILL BE WITH THE PASSAGE OF THE FRONT
TODAY. WITH LAKE AND SEA BREEZES LIKELY AT MIDDAY...AND THE FRONT
MOVING INTO THE AREA...FEEL THERE WILL BE ENOUGH LOW LEVEL
CONVERGENCE TO WORK ON THE SLIGHTLY MORE MOIST AIR TO PRODUCE
ISOLATED TO SCATTERED CONVECTION THIS AFTERNOON NEAR THE FRONT.
WILL CONTINUE WITH A RIBBON OF CHANCE POPS NEAR WHERE LAKE AND SEA
BREEZES ARE EXPECTED...WITH LOWER POPS TO EITHER SIDE. EXPECT
PRECIPITATION WILL MOVE OFFSHORE DURING THE EVENING HOURS. MODEL
SOLUTIONS ARE DRY FOR TUESDAY...BUT CANNOT RULE OUT SOME VERY
ISOLATED PRECIPITATION OVER LOWER PORTIONS OF THE COASTAL PARISHES
WEDNESDAY.

THE DRIER AIR MOVING INTO THE AREA SHOULD PROVIDE LOW TEMPERATURES
THAT ARE ACTUALLY BELOW NORMAL FOR MUCH OF THE AREA THE NEXT
COUPLE NIGHTS. DIURNAL TEMPERATURE SPREADS WILL BE A LITTLE LARGER
THAN NORMAL...ABOUT 25 DEGREES...SO HIGH TEMPERATURES ARE LIKELY
TO END UP RELATIVELY CLOSE TO NORMAL...OR POSSIBLY A LITTLE
ABOVE...THROUGH WEDNESDAY. 35

&&

.LONG TERM...

WEAK UPPER RIDGING OVER THE LOWER MISSISSIPPI RIVER VALLEY SHOULD
HOLD THE MOISTURE RETURN AT BAY A LITTLE LONGER THAN PREVIOUS
FORECAST PACKAGE WOULD INDICATE. ECMWF AND GFS SOLUTIONS KEEP RAIN
CHANCES BELOW 20 PERCENT AT MOST ALL LAND BASED STATIONS UNTIL
SATURDAY AFTERNOON. HAVE BACKED POPS DOWN QUITE A BIT FOR THURSDAY
AND FRIDAY. WILL CONTINUE THE PREVIOUS CHANCE POPS MENTION FOR
SATURDAY AND SUNDAY AS GREAT PLAINS SYSTEM WILL GRADUALLY MOVE
ACROSS THE LOWER MISSISSIPPI RIVER VALLEY NEXT WEEKEND. DEPENDING
ON YOUR MODEL OF CHOICE...THE BACK END OF THE RAIN THREAT WILL
MOVE THROUGH THE AREA SUNDAY NIGHT OR MONDAY...WITH THE ECMWF
SOLUTION ABOUT 12 HOURS SLOWER. CURRENT FORECAST IS TRENDED TOWARD
THIS SOLUTION.

EXPECT TEMPERATURES TO BE NEAR TO SLIGHTLY WARMER THAN NORMAL
DURING THE EXTENDED FORECAST PERIOD...ALTHOUGH IF STRENGTH OF
UPPER SYSTEM DEPICTED BY ECMWF IS CORRECT...HIGH TEMPERATURES FOR
SUNDAY AND MONDAY MAY NEED TO BE LOWERED A BIT DUE TO ADDITIONAL
CLOUD COVER. 35

&&

.AVIATION...

MAINLY VFR CONDITIONS WILL PREVAIL AT THE TERMINALS THROUGH THE TAF
FORECAST PERIOD...HOWEVER A PERIOD OF MVFR VSBYS DUE TO PATCHY FOG
WILL BE POSSIBLE AT A COUPLE TAF AIRPORTS THROUGH ABOUT 13Z TODAY.
A COLD FRONT WILL MOVE FROM NORTH TO SOUTH THROUGH THE TAF AIRPORTS
TODAY. ISOLATED TO SCATTERED SHRA AND SOME TSRA ARE EXPECTED TO
DEVELOP BY MIDDAY JUST AHEAD OF THE FRONT...HOWEVER IMPACTS ON THE
TERMINALS SHOULD BE BRIEF DUE TO LIMITED COVERAGE AND FAIRLY QUICK
MOVEMENT. HAVE OPTED NOT TO INCLUDE MENTION IN THE TAFS AT THIS
TIME...BUT SOME MENTION MAY BE NEEDED LATER AS RADAR TRENDS ARE
ESTABLISHED. MAINLY CLEAR SKIES AND UNRESTRICTED VSBYS ARE EXPECTED
BEHIND THE FRONT GOING INTO TONIGHT AND THE NEXT COUPLE DAYS. 22/TD

&&

.MARINE...

THERE IS A LULL IN WINDS AND WAVE HEIGHTS AT THE MOMENT DUE TO A
RELAXED PRESSURE GRADIENT...AND THAT WILL REMAIN THE CASE THROUGH
MOST OF THE DAY TODAY. WINDS TODAY ARE EXPECTED TO RANGE FROM 5 TO
10 KNOTS ACROSS TIDAL LAKES AND SOUNDS...AND MOSTLY 10 TO 15 KNOTS
ACROSS THE COASTAL WATERS WITH WAVE HEIGHTS MOSTLY IN THE 1 TO 3
FEET RANGE.

THE FIRST STRONG COLD FRONT OF AUTUMN WILL APPROACH THE CENTRAL GULF
COAST FROM THE NORTH THIS AFTERNOON THEN PUSH ACROSS THE COASTAL
WATERS FROM NORTH TO SOUTH TONIGHT. NORTHEAST WINDS ARE EXPECTED TO
RISE TO NEAR 20 KNOTS OR 20 TO 25 KNOTS ACROSS THE TIDAL
LAKES...SOUNDS...AND COASTAL WATERS NORTHEAST OF SOUTHWEST PASS BY
AROUND 10 PM TONIGHT...SO HAVE ISSUED A SMALL CRAFT ADVISORY FOR THE
LAKES AND SOUNDS FROM 10 PM THROUGH 7 AM TUESDAY. THESE WATERS
SHOULD DROP JUST BELOW SMALL CRAFT CRITERIA MOST OF THE DAY ON
TUESDAY...HOWEVER HEADLINES OF AT LEAST /SMALL CRAFT EXERCISE
CAUTION/ WILL NEED TO BE ADDED LATER...AND SMALL CRAFT ADVISORIES
ARE LIKELY GOING TO HAVE TO BE REISSUED FOR LATE TUESDAY NIGHT AND
WEDNESDAY.

FOR THE COASTAL WATERS...A SMALL CRAFT ADVISORY WILL BE IN EFFECT
FOR THE EASTERN MARINE ZONES FROM 10 PM TONIGHT THROUGH
WEDNESDAY...AND THIS WILL LIKELY NEED TO BE EXPANDED IN AREA AND
EVENTUALLY LATER IN TIME AS A STOUT PRESSURE GRADIENT IS EXPECTED TO
PERSIST BETWEEN AN EXPANSIVE HIGH PRESSURE AREA OVER THE EASTERN
STATES AND LOWER PRESSURES OVER THE GULF OF MEXICO. EAST TO
NORTHEAST WINDS WILL BRIDGE ACROSS THE STALLED FRONTAL BOUNDARY
OFFSHORE...HOWEVER THE STRONG BAROCLINICITY AND EASTERLY
WAVE/INVERTED TROUGH FEATURES MAY LOCALLY ENHANCE THE PRESSURE
GRADIENT AND WIND SPEEDS THROUGH EARLY SATURDAY...HOWEVER THE MODELS
ALL AGREE THE WINDS AND WAVE HEIGHTS SHOULD BE WELL BELOW SMALL
CRAFT ADVISORY CRITERIA OVER THE WEEKEND. 22/TD

&&

.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  58  85  61 /  10  10  10  10
BTR  89  60  85  62 /  20  10  10  10
ASD  89  62  86  64 /  30  10  10  10
MSY  89  70  84  71 /  30  10  10  10
GPT  89  64  85  66 /  30  10  10  10
PQL  88  60  85  64 /  30  10  10  10

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...NONE.
GM...SMALL CRAFT ADVISORY FROM 10 PM MONDAY TO 7 AM TUESDAY FOR THE
     FOLLOWING ZONES: BRETON SOUND...CHANDELEUR SOUND...LAKE
     BORGNE...LAKE PONTCHARTRAIN AND LAKE MAUREPAS...AND
     MISSISSIPPI SOUND.

     SMALL CRAFT ADVISORY FROM 10 PM MONDAY TO 7 PM WEDNESDAY FOR THE
     FOLLOWING ZONES: COASTAL WATERS FROM PASCAGOULA MS TO STAKE
     ISLAND LA FROM 20 TO 60 NM...AND COASTAL WATERS FROM
     PASCAGOULA MS TO STAKE ISLAND LA OUT 20 NM.

MS...NONE.
GM...SMALL CRAFT ADVISORY FROM 10 PM MONDAY TO 7 AM TUESDAY FOR THE
     FOLLOWING ZONES: BRETON SOUND...CHANDELEUR SOUND...LAKE
     BORGNE...LAKE PONTCHARTRAIN AND LAKE MAUREPAS...AND
     MISSISSIPPI SOUND.

     SMALL CRAFT ADVISORY FROM 10 PM MONDAY TO 7 PM WEDNESDAY FOR THE
     FOLLOWING ZONES: COASTAL WATERS FROM PASCAGOULA MS TO STAKE
     ISLAND LA FROM 20 TO 60 NM...AND COASTAL WATERS FROM
     PASCAGOULA MS TO STAKE ISLAND LA OUT 20 NM.

&&

$$







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