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

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284
FXUS64 KLIX 271818
AFDLIX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
118 PM CDT SAT SEP 27 2014

.MARINE...

HAVE ISSUED A SMALL CRAFT ADVISORY FOR THE EASTERN LEGS OF THE
MARINE ZONES. AN INCREASING PRESSURE GRADIENT OVER THIS AREA HAS
ALLOWED FOR WINDS TO RISE TO 20 TO 25 KNOTS AND SEAS TO INCREASE
TO AROUND 7 FEET AS NOTED BY BUOY 42040. WINDS AND SEAS HAVE
ADJUSTED TO REFLECT THE TREND OVER THE LAST FEW HOURS...BUT STILL
EXPECT TO SEE A DECREASE IN THE OVERALL GRADIENT FLOW BY THE
EVENING HOURS AS THE PRESSURE GRADIENT OVER THE GULF EASES. 32

&&

.PREV DISCUSSION... /ISSUED 810 AM CDT SAT SEP 27 2014/

..SOUNDING DISCUSSION...

SHORTLY AFTER BALLOON RELEASE RH WAS LOST FOR AN UNKNOWN REASON
AND THIS IS WHY THERE IS NO DEWPOINT PROFILE ON THIS MORNING/S
SOUNDING. THE LACK OF THIS DATA MEANS THAT MANY CONVECTIVE
PARAMETERS /CONVECTIVE TEMP...LI/TT/K INDEX...ETC/ AND THE
PRECIPITABLE WATER VALUE ARE ERRONEOUS. MODELED PW VALUES AT
LAUNCH TIME WERE BETWEEN 1.2 AND 1.4 INCHES. BY THIS EVENING/S
BALLOON...PW VALUES SHOULD BE AROUND 2 INCHES /1.8 INCHES IN 11Z
RUC TO 2.3 INCHES IN 3Z SREF/6Z GFS/.

THERE WERE TWO TEMPERATURE INVERSION. THE FIRST BEING THE SURFACE
INVERSION AND THE OTHER INVERSION BEING LOCATED BETWEEN 860 AND
820MB. A NICE VEERING PROFILE THIS MORNING AS WINDS WERE FROM
THE NORTHEAST NEAR THE SURFACE AND THEN BECAME FROM THE SOUTHWEST
AROUND 8000 FEET ON UP TO THE TROPOPAUSE. THESE SOUTHWESTERLY
WINDS WILL MOVE A VERY MOIST AIRMASS IN BY LATE TODAY. A PEAK
WIND OF 44 KNOTS WAS FOUND AT 37000 FEET ABOVE THE GROUND.

12Z BALLOON INFO: OUTSIDE OF THE RH ISSUE MENTIONED ABOVE THE
FLIGHT WAS SUCCESSFUL. THE BALLOON ASCENDED FOR 109 MINUTES TO A
HEIGHT OF 21.2 MILES ABOVE THE GROUND AND BURST OVER THE SOUTHERN
PART OF PICAYUNE 14 MILES DOWNRANGE.

ANSORGE

PREV DISCUSSION... /ISSUED 329 AM CDT SAT SEP 27 2014/

SYNOPSIS...

AS HAS BEEN THE CASE THE LAST SEVERAL MORNINGS...HIGH PRESSURE
REMAINS PARKED OVER THE GREAT LAKES. REMNANTS OF THE OLD COLD
FRONT REMAIN PARKED OVER THE NORTHERN GULF AROUND 27N.
ALOFT...WEAK UPPER LOWS ARE OVER IOWA AND WEST TEXAS. ANOTHER WEAK
TROF EXTENDS FROM BERMUDA SOUTHWESTWARD ACROSS FLORIDA INTO THE
CENTRAL GULF. CONVECTION IS MAINLY CONFINED TO THE WESTERN
GULF...BUT A CONSIDERABLE AMOUNT OF CIRRUS CONTINUES TO GET
TRANSPORTED NORTHEAST ACROSS THE AREA. THERE ARE MORE BREAKS IN
THE CIRRUS THIS MORNING...WHICH HAS ALLOWED TEMPERATURES TO FALL
INTO THE MIDDLE 60S AWAY FROM MARINE INFLUENCES.

SHORT TERM...

UPPER LOW OVER TEXAS FINALLY BEGINS LIFTING OUT TODAY AND TONIGHT.
THIS...COMBINED WITH THE TROF OVER THE EASTERN GULF...WILL INCREASE
MOISTURE LEVELS AND PROVIDE SUFFICIENT FORCING TO DEVELOP
PRECIPITATION ACROSS THE AREA BEGINNING THIS AFTERNOON AND
CONTINUING THROUGH A GOOD PORTION OF SUNDAY. THE BEST INGREDIENTS
FOR PRECIPITATION WILL BE OVER EASTERN PORTIONS OF THE
AREA...WHERE LIKELY TO CATEGORICAL POPS WILL BE IN PLACE. GFS BUFR
SOUNDINGS QUICKLY RAISE PRECIPITABLE WATER VALUES TO AROUND 2
INCHES BY LATE AFTERNOON...WHILE NAM IS SOMEWHAT SLOWER. HAVE
TRENDED TOWARD THE WETTER ECMWF/GFS SOLUTIONS AND AWAY FROM THE
NAM SOLUTION. CERTAINLY SOME POTENTIAL FOR LOCALLY HEAVY
RAINFALL...BUT ANTECEDENT CONDITIONS ARE DRY AND MUCH OF THE
HEAVIER RAINFALL WILL REMAIN OFFSHORE OR TO THE EAST OF THE AREA.
THERE REMAINS AT LEAST SOME POTENTIAL FOR A BUSTED POP FORECAST IF
CONVECTION DEVELOPS OFFSHORE AND REMAINS THERE.

UPPER SYSTEM SHOULD BE LIFTING EAST OF THE AREA BY SUNDAY EVENING
WITH DRYING CONDITIONS FOR MONDAY. GUIDANCE TEMPERATURES ARE
PRETTY CLOSE FOR TODAY AND TONIGHT. GENERALLY...GFS/MAV GUIDANCE
LOOKS TOO WARM ON HIGHS FOR SUNDAY. HAVE UNDERCUT SOMEWHAT AND MAY
STILL NOT BE COOL ENOUGH FOR SUNDAY...WHERE PRECIPITATION COULD
HOLD TEMPERATURES IN SOME AREAS BELOW 80 DEGREES. PARTLY SUNNY
SKIES ON MONDAY SHOULD ALLOW TEMPERATURES TO RECOVER INTO THE
MIDDLE 80S. 35

LONG TERM...

UPPER RIDGE WILL TRAVERSE THE AREA AT MIDWEEK WITH A COUPLE OF DRY
DAYS TUESDAY AND WEDNESDAY. MEX NUMBERS APPEAR TO BE SOMEWHAT TOO
WARM ON TUESDAY AND WEDNESDAY...AND HAVE BACKED THOSE OFF A FEW
DEGREES. SHORTWAVES MOVING ACROSS THE NORTHERN HALF OF THE COUNTRY
ARE INCREASING IN AMPLITUDE AT THE END OF THE WEEK AS A WESTERN
RIDGE-EASTERN TROF PATTERN RE-EMERGES. THIS WILL DRIVE A COLD
FRONT THROUGH THE AREA ON FRIDAY NIGHT. GFS AND ECMWF ARE IN
FAIRLY DECENT AGREEMENT ON TIMING OF THIS FEATURE. SHOWERS AND
THUNDERSTORMS ARE POSSIBLE IN ADVANCE OF THE FRONT AS EARLY AS
THURSDAY AFTERNOON. FOR NOW...WILL CARRY CHANCE POPS FOR THURSDAY
THROUGH FRIDAY. LATER FORECASTS ARE LIKELY TO RAISE POPS SOMEWHAT
FOR AT LEAST ONE PERIOD DURING THAT TIME AS FRONTAL TIMING BECOMES
MORE ESTABLISHED. 1000-500MB THICKNESS VALUES DROP IN EXCESS OF
100 METERS FROM FRIDAY TO SUNDAY...AND 850MB TEMPERATURES DROP
FROM 16-18C TO 10-12C...WHICH WOULD INDICATE TEMPERATURES COOLING
10F OR MORE BY SUNDAY. WILL BE HOLDING TEMPERATURES IN THE MIDDLE
AND UPPER 70S FOR SATURDAY AND SUNDAY...WITH LOWS NEXT SUNDAY
MORNING LIKELY IN THE MIDDLE 50S ACROSS NORTHWEST PORTIONS OF THE
AREA. 35

AVIATION...

VFR CONDITIONS ARE GENERALLY EXPECTED AT THE TERMINALS TODAY...
HOWEVER THE THREAT FOR SHOWERS AND THUNDERSTORMS WILL BE INCREASING
AS THE AFTERNOON PROGRESSES...PARTICULARLY AT TAF SITES SITES CLOSER
TO THE COAST. THE BETTER CHANCE FOR RAIN...HOWEVER...WILL HOLD OFF
UNTIL AFTER 00Z SUNDAY WHEN NUMEROUS SHOWERS AND THUNDERSTORMS ARE
EXPECTED OVERNIGHT AND DURING THE EARLY MORNING HOURS SUNDAY ACROSS
THE SOUTHEAST HALF OF THE FORECAST AREA. THE ACTIVITY WILL BE MORE
SCATTERED IN NATURE ACROSS THE NORTHWEST HALF OF THE AREA. MVFR
CEILINGS ARE GENERALLY EXPECTED BETWEEN 06Z AND 12Z SUNDAY. 11

MARINE...

MODERATE EASTERLY FLOW ACROSS THE COASTAL WATERS THIS MORNING WILL
BEGIN TO DIMINISH LATE TODAY AND TONIGHT. EXERCISE CAUTION HEADLINES
WILL BE MAINTAINED FOR SOME OF THE OUTER COASTAL WATERS EAST OF THE
MISSISSIPPI RIVER TODAY. WINDS WILL BECOME LIGHT AND MORE VARIABLE
LATER TONIGHT AND SUNDAY AS AN INVERTED TROUGH OR WEAK AREA OF LOW
PRESSURE MOVES SLOWLY ACROSS THE COASTAL WATERS. THIS FEATURE WILL
BRING WIDESPREAD SHOWER AND THUNDERSTORM ACTIVITY TO THE COASTAL
WATERS LATER TODAY THROUGH SUNDAY. WINDS WILL TURN NORTHERLY MONDAY
IN THE WAKE OF THE DEPARTING TROUGH/LOW PRESSURE AREA. SEAS OF 2 TO
4 FEET TODAY WILL SUBSIDE TO 1 TO 2 FEET LATE TONIGHT AND SUNDAY.
WINDS BE LIGHT AND SEAS LOW DURING THE EARLY AND MID PART OF THE
UPCOMING WORK WEEK WITH WEAK HIGH PRESSURE OVER THE AREA. 11

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  83  67  80  65 /  20  50  50  20
BTR  84  68  84  66 /  20  40  40  20
ASD  85  68  82  65 /  40  70  70  30
MSY  83  73  82  71 /  40  60  60  30
GPT  85  71  81  66 /  50  80  80  30
PQL  85  70  81  65 /  50  90  80  40

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...NONE.
GM...SMALL CRAFT ADVISORY UNTIL 7 PM SATURDAY FOR THE FOLLOWING
     ZONES: COASTAL WATERS FROM BOOTHVILLE LA TO THE SOUTHWEST
     PASS OF THE MISSISSIPPI RIVER OUT 20 NM...COASTAL WATERS
     FROM PASCAGOULA MS TO STAKE ISLAND LA FROM 20 TO 60
     NM...COASTAL WATERS FROM PASCAGOULA MS TO STAKE ISLAND LA
     OUT 20 NM...AND COASTAL WATERS FROM STAKE ISLAND LA TO THE
     SOUTHWEST PASS OF THE MISSISSIPPI RIVER FROM 20 TO 60 NM.

MS...NONE.
GM...SMALL CRAFT ADVISORY UNTIL 7 PM SATURDAY FOR THE FOLLOWING
     ZONES: COASTAL WATERS FROM BOOTHVILLE LA TO THE SOUTHWEST
     PASS OF THE MISSISSIPPI RIVER OUT 20 NM...COASTAL WATERS
     FROM PASCAGOULA MS TO STAKE ISLAND LA FROM 20 TO 60
     NM...COASTAL WATERS FROM PASCAGOULA MS TO STAKE ISLAND LA
     OUT 20 NM...AND COASTAL WATERS FROM STAKE ISLAND LA TO THE
     SOUTHWEST PASS OF THE MISSISSIPPI RIVER FROM 20 TO 60 NM.

&&

$$







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