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

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725
FXUS64 KLIX 251308
AFDLIX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
808 AM CDT THU SEP 25 2014

...SOUNDING DISCUSSION...

SUCCESSFUL BALLOON LAUNCH THIS MORNING FROM WFO SLIDELL. CLEAR AND DRY
CONDITIONS PERSIST IN THE AREA DOWN 2 STANDARD DEVIATIONS BELOW
NORMAL FOR MOISTURE CONTENT. EARLY MORNING MOISTURE AND DEW AT THE
SURFACE FOLLOWED BY A STRONG INVERSION WITH EASTERLY WINDS UP TO
20 KTS IN THE LOWER LEVELS. MID LEVEL WIND FIELD UP TO 500MB WAS
PRIMARILY NORTHERLY OTHERWISE LIGHT & VRBL. 400 MB LEVEL UP TO BALLOON
TERMINATION WAS SUMMARIZED IN SOUTHWEST WINDS VARYING IN STRENGTH
UP TO 45 KTS PEAK NEAR 250 MB THEN REDIRECTED BACK TOWARD THE WFO
SLIDELL AS A RESULT OF CONSISTENT NE WIND FLOW. MAX HEIGHT
ACHIEVED BY BALLOON REACH 33500 METERS.

MGW

.PREV DISCUSSION... /ISSUED 302 AM CDT THU SEP 25 2014/

SYNOPSIS...

AT THE SURFACE...HIGH PRESSURE CONTINUES TO BE CENTERED OVER NEW
ENGLAND WITH A RIDGE AXIS SOUTHWEST TO TEXAS. A WEAK INVERTED TROF
IS LOCATED ALONG THE CAROLINA COAST. A WEAK LOW PRESSURE CENTER
ALSO APPEARS TO BE CENTERED OVER THE WESTERN GULF OF MEXICO NEAR
BROWNSVILLE.

ALOFT...A WEAK TROF EXTENDS FROM WISCONSIN SOUTHWEST TO THE TEXAS
PANHANDLE. ANOTHER WEAK TROF IS LOCATED OVER THE CENTRAL GULF OF
MEXICO AND HAS CONVECTION ASSOCIATED WITH IT TO THE SOUTH AND
SOUTHWEST OF OUR COASTAL WATERS.

QUITE A BIT OF CIRRUS ACROSS ABOUT THE SOUTHERN THREE QUARTERS OF
THE AREA IS LIKELY HOLDING TEMPERATURES UP SOMEWHAT FROM THE
PREVIOUS TWO NIGHTS. READINGS ARE GENERALLY IN THE 60S AWAY FROM
MARINE INFLUENCES.

SHORT TERM...

EXPECT CIRRUS SHIELD TO REMAIN ACROSS MOST OF THE AREA THROUGH
SATURDAY...SOMEWHAT RESTRICTING DIURNAL TEMPERATURE SPREADS. UPPER
TROFFING FROM WISCONSIN TO TEXAS IS EXPECTED TO REMAIN IN THAT
GENERAL AREA THROUGH SATURDAY. HOWEVER...THE FLOW AROUND IT WILL
PULL MOISTURE NORTHWARD FROM THE GULF INTO THE AREA...AS WELL AS A
COUPLE OF WEAK IMPULSES. PRECIPITABLE WATER VALUES CURRENTLY NEAR ONE
INCH WILL INCREASE TO 2-2.25 INCHES BY SATURDAY EVENING.

FOR THE FIRST 48 HOURS...THROUGH FRIDAY NIGHT...HAVE NOT MADE MUCH
CHANGE FROM PREVIOUS FORECAST. HAVE BUMPED UP POPS FOR SATURDAY
FROM PREVIOUS FORECAST AS MODELS ARE IN DECENT AGREEMENT ON
FORECAST SCENARIO. ACTUALLY ABOVE NAM/GFS MOS GUIDANCE IN MOST
AREAS ON SATURDAY...BUT NOT QUITE AS HIGH AS SOME OF THE ECMWF MOS
GUIDANCE WOULD INDICATE. IN FAIRLY GOOD AGREEMENT WITH MOST OF THE
NEIGHBORING OFFICES WITH RESPECT TO POPS ON SATURDAY.

HAVE NOT HAD TO MAKE MANY CHANGES TO TEMPERATURE FORECAST OVER THE
NEXT 48 HOURS. CIRRUS WILL HOLD TEMPERATURES BACK FROM MAXING OUT
THEIR POTENTIAL. GENERALLY HAVE TRENDED BELOW THE WARMER
GUIDANCE...AND IT IS POSSIBLE SATURDAY HIGH TEMPERATURES MAY HAVE
TO BE LOWERED A LITTLE BIT MORE IF PRECIPITATION DEVELOPS EARLIER
THAN ANTICIPATED. 35

LONG TERM...

AS TROF OVER THE GREAT PLAINS FINALLY LIFTS OUT SUNDAY AND
MONDAY...IT WILL PULL ONE LAST UPPER AND SURFACE IMPULSE ACROSS
THE AREA SUNDAY AND SUNDAY NIGHT. SOME DIFFERENCES IN EXACT
DETAILS BETWEEN ECMWF AND GFS...WITH EITHER SCENARIO A REASONABLE
SOLUTION. WILL CARRY POPS IN THE 40-60 RANGE FOR SUNDAY...WITH
SOMEWHAT LOWER POPS FOR SUNDAY NIGHT. MINIMAL MENTION OF RAIN ON
MONDAY...AND ECMWF SOLUTION WOULD HAVE US DRY FOR MONDAY. CAN
CONTINUE TO TRACK THAT TREND IN LATER FORECASTS. WEAK UPPER
RIDGING FOLLOWS FOR MUCH OF THE FOLLOWING WORKWEEK. CANNOT RULE
OUT AT LEAST ISOLATED PRECIPITATION POTENTIAL FOR TUESDAY AND
WEDNESDAY...BUT AGAIN ECMWF SOLUTION WOULD HAVE US DRY. A NEW
STRONG UPPER TROF WILL ENTER THE GREAT PLAINS ON THURSDAY...AND AS
THE LOW LEVEL GRADIENT INCREASES...MOISTURE WILL RETURN AS WILL
THE CHANCES FOR RAIN. MODEL SOLUTIONS DIVERGE ON SYSTEM SPEED FOR
NEXT WEEKEND...BUT THAT IS BEYOND THE REALM OF THE CURRENT
FORECAST PACKAGE. TEMPERATURES WILL REMAIN NEAR TO ABOVE NORMAL
FOR THE EXTENDED PERIOD. 35

AVIATION...

VFR CONDITIONS ARE GENERALLY EXPECTED AT THE TERMINALS THROUGH THE
TAF FORECAST PERIOD. THE POSSIBLE EXCEPTION WOULD BE A PERIOD OF
MVFR VSBYS DUE TO PATCHY FOG AT THE MORE FOG PRONE TAF SITES DURING
THE EARLY MORNING HOURS PRIOR TO AND AROUND SUNRISE. 11

MARINE...

A LARGE HIGH PRESSURE RIDGE COVERING THE EASTERN U.S. WILL PERSIST
THROUGH SATURDAY. MEANWHILE...A WEAK INVERTED TROUGH WILL DEVELOP
OVER THE SOUTHWEST AND CENTRAL GULF. THESE TWO FEATURES WILL
MAINTAIN A MODERATE TO OCCASIONALLY STRONG EASTERLY FETCH ACROSS THE
NORTH GULF THROUGH THE END OF THE WEEK. A SMALL CRAFT ADVISORY FOR
THE OUTER WATERS EAST OF THE MISSISSIPPI RIVER WILL CONTINUE UNTIL 7
AM WITH EXERCISE CAUTION HEADLINES ELSEWHERE. AFTER 7 AM...EXERCISE
CAUTION HEADLINES BE MAINTAINED FOR MOST ALL OF THE GULF COASTAL
WATERS THROUGH THE MORNING HOURS...AND FOR THE JUST THE OUTER WATERS
DURING THE AFTERNOON. THE PRESSURE GRADIENT SHOULD WEAKEN TO BRING
WINDS DOWN TO AROUND 10 KNOTS OR LESS SUNDAY AFTERNOON INTO EARLY
NEXT WEEK AS HIGH PRESSURE WEAKENS AND A WEAK TROUGH MOVES OVER THE
CENTRAL GULF COAST REGION. WITH THE WEAK TROUGH OVER THE AREA DURING
THE THE WEEKEND...NUMEROUS SHOWERS AND THUNDERSTORMS ARE EXPECTED
ACROSS THE COASTAL WATERS. 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  85  63  87  66 /   0   0   0  10
BTR  87  64  88  68 /   0   0   0  10
ASD  86  64  88  68 /  10   0  10  20
MSY  85  71  87  72 /  10   0  10  20
GPT  85  65  87  70 /  10   0  10  10
PQL  85  62  87  68 /  10   0   0  10

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...NONE.
GM...SMALL CRAFT ADVISORY UNTIL 7 AM THURSDAY 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 UNTIL 7 AM THURSDAY 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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