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

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554
FXUS64 KLIX 260458
AFDLIX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
1158 PM CDT THU SEP 25 2014

.UPDATE...
HAVE MADE ONLY A FEW MINOR UPDATES TO ACCOUNT FOR TEMPERATURE AND
SKY COVER TRENDS...OTHERWISE CURRENT FORECAST IS ON TRACK.
AVIATION WISE EXPECT VFR CONDITIONS TO PREVAIL THROUGH THE ENTIRE
FORECAST PERIOD. 13/MH

&&

.PREV DISCUSSION... /ISSUED 356 PM CDT THU SEP 25 2014/

SHORT TERM...

A DRY AND STABLE AIRMASS WILL REMAIN OVER THE FORECAST AREA
THROUGH TOMORROW AS A STRONG MID-LEVEL RIDGE AXIS REMAINS CENTERED
OVER THE CENTRAL GULF COAST. WITH THE RIDGE AND DRY AIR IN
PLACE...A STRONG MID-LEVEL CAP WILL REMAIN IN PLACE THROUGH THE
AFTERNOON HOURS TOMORROW. AS A RESULT...LITTLE IN THE WAY OF CLOUD
DEVELOPMENT IS EXPECTED IN THE LOW AND MID-LEVELS OF THE
ATMOSPHERE. ONLY SOME HIGH LEVEL CLOUD COVER ASSOCIATED WITH BLOW
OFF FROM A CONVECTIVE COMPLEX OVER EASTERN TEXAS AND THE WESTERN
GULF OF MEXICO WILL SPREAD ACROSS THE AREA THROUGH TOMORROW.
TEMPERATURES WILL GENERALLY RANGE NEAR SEASONAL NORMS TONIGHT AND
TOMORROW.

HEADING INTO TOMORROW NIGHT...THE MID-LEVEL RIDGE AXIS WILL PULL
AWAY FROM THE AREA. THIS WILL ALLOW AN INVERTED MID-LEVEL TROUGH
CURRENTLY OVER FLORIDA TO PULL WESTWARD INTO THE CENTRAL AND
EASTERN GULF OF MEXICO TOMORROW NIGHT. STILL EXPECT TO SEE ENOUGH
MID-LEVEL DRY AIR REMAIN IN PLACE TO KEEP ANY CONVECTIVE
DEVELOPMENT AT BAY...BUT SOME ISOLATED SHOWER MAY TRY TO DEVELOP
LATE SATURDAY NIGHT OVER THE OFFSHORE COASTAL WATERS. THIS TROUGH
AXIS WILL CONTINUE TO PULL CLOSER TO THE GULF COAST ON
SATURDAY...AND HAVE INCREASING POPS MOVE INTO THE FORECAST AREA
THROUGH THE DAY. BY SATURDAY AFTERNOON...SCATTERED CONVECTION
SHOULD BE FOUND ALONG THE LOUISIANA AND MISSISSIPPI COAST WITH
MORE ISOLATED COVERAGE FURTHER INLAND.

HEADING INTO SATURDAY NIGHT AND SUNDAY...HAVE DECIDED TO GO WITH A
50/50 MODEL BLEND OF THE ECMWF AND THE GFS SOLUTIONS. THE GFS HAS
A DRIER SOLUTION OVER THE FORECAST AREA...WITH THE TROUGH AXIS
POSITIONED MORE TOWARD THE ALABAMA COAST. HOWEVER...THE ECMWF HAS
THE MID-LEVEL TROUGH FIRMLY ENTRENCHED ACROSS SOUTHEAST LOUISIANA.
GIVEN THE TIGHT PRECIPITATION GRADIENT ON THE WESTERN OR MORE
SUBSIDENT SIDE OF THE TROUGH AXIS...HAVE OPTED TO GO WITH THE
MODEL BLEND AS A 100 MILE DIFFERENCE IN THE POSITION OF THE TROUGH
COULD MAKE FOR A SIGNIFICANT CHANGE IN RAIN CHANCES. WITH THIS
MODEL BLEND IN MIND...HAVE CHANCE POPS OVERSPREAD ALL OF THE
INLAND AREAS BY LATE SATURDAY NIGHT...AND LIKELY POPS DEVELOPING
ALONG THE LOUISIANA AND MISSISSIPPI COASTS.

BOTH MODELS INDICATE THAT SOME SHORT-WAVE ENERGY IN THE UPPER
LEVELS WILL KICK OUT OF TEXAS AND PULL THROUGH THE AREA ON SUNDAY.
THIS SYSTEM WILL ALLOW FOR THE DEVELOPMENT OF A WEAK LOW IN THE
MID-LEVELS BY SUNDAY AFTERNOON AND THE LOW LEVELS ON MONDAY. AS
THIS LOW FORMS...DRIER AIR WILL WRAP AROUND THE SYSTEM...AND BEGIN
TO SPREAD INTO WESTERN ZONES BY SUNDAY AFTERNOON. HOWEVER...EXPECT
TO SEE LIKELY POPS OVER MOST OF THE FORECAST AREA SUNDAY MORNING
IN ADVANCE OF THIS UPPER LEVEL FEATURE. ALONG THE MISSISSIPPI
COAST...CATEGORICAL POPS HAVE BEEN INTRODUCED THROUGH THE DAY.
SOME OF THE RAINFALL MAY BE LOCALLY HEAVY ALONG THE MISSISSIPPI
COAST AS STORMS TRAIN OVER THE SAME LOCATIONS. AS THE LOW PULLS TO
THE EAST OF THE AREA SUNDAY NIGHT INTO EARLY MONDAY...AND DRIER
AIR AND INCREASED UPPER LEVEL SUBSIDENCE BEGINS TO ADVECT INTO THE
AREA...EXPECT TO SEE RAIN CHANCES DECREASE THROUGHOUT THE NIGHT
SUNDAY NIGHT INTO EARLY MONDAY FROM WEST TO EAST.

LONG TERM...

A SHORT WAVE RIDGE AXIS WILL SPREAD OVER THE AREA ON TUESDAY
BRINGING DRIER AIR AND INCREASED SUBSIDENCE TO THE AREA. AS A
RESULT...HAVE NO MENTION OF RAINFALL FOR TUESDAY...AND EXPECT TO
SEE ONLY LIMITED CLOUD COVER DEVELOPMENT BELOW THE MID-LEVEL CAP.
THIS RIDGE WILL LINGER INTO TUESDAY NIGHT...BUT WILL BEGIN TO
WEAKEN ON WEDNESDAY AND SHIFT TOWARD THE SOUTHEASTERN CONUS. AS
THIS OCCURS...THE MID-LEVEL CAP WILL WEAKEN. THIS WEAKENING OF THE
CAP COULD ALLOW FOR SOME ISOLATED CONVECTIVE ACTIVITY TO DEVELOP
DURING THE PEAK HEATING HOURS.

A WEAK SHORT WAVE TROUGH WILL THEN SLIDE THROUGH THE AREA ON
THURSDAY. THIS WEAK TROUGH SHOULD PROVIDE ENOUGH LIFT ACROSS THE
AREA TO SPARK OFF SCATTERED CONVECTION. THE CONVECTION WILL BE
MOST LIKELY DURING THE AFTERNOON HOURS WHEN OVERALL INSTABILITY IS
MAXIMIZED. TEMPERATURES WILL GENERALLY RANGE NEAR SEASONAL NORMS
THROUGH THE EXTENDED FORECAST PERIOD WITH HIGHS IN THE MIDDLE TO
UPPER 80S AND LOWS IN THE UPPER 60S AND LOWER 70S.

&&

MARINE...

THE COMBINATION OF RIDGE OVER THE GULF SOUTH AND A BROAD AREA OF
LOW PRESSURE OVER THE CENTRAL AND EASTERN GULF OF MEXICO WILL KEEP
PERSISTENT EASTERLY FLOW OF AROUND 15 KNOTS IN PLACE ACROSS THE
GULF COASTAL WATERS THROUGH SATURDAY. SEAS WILL GENERALLY RANGE
FROM 3 TO 5 FEET TONIGHT...BUT SHOULD DECREASE TO 2 TO 4 FEET FOR
FRIDAY AND SATURDAY. OVER THE LAKES AND SOUNDS...WINDS WILL RANGE
CLOSER TO 10 KNOTS DURING THIS PERIOD. A WEAK AREA OF LOW PRESSURE
WILL BEGIN TO FORM OVER THE COASTAL WATERS ON SUNDAY AND THE HIGH
OVER THE SOUTHEAST WILL MOVE AWAY FROM THE AREA. AS A
RESULT...GRADIENT FLOW WILL WEAKEN AND TURN MORE VARIABLE SUNDAY
INTO SUNDAY NIGHT. WINDS SHOULD TURN MORE NORTHERLY BY MONDAY IN
THE WAKE OF THE DEPARTING LOW AS SOME DRIER AIR ADVECTS INTO THE
AREA FROM THE NORTH. SEAS WILL FALL BACK TO AROUND 1 TO 2 FEET
DURING THIS PERIOD.

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  61  85  64  85 /   0   0  10  20
BTR  65  85  67  85 /   0   0  10  20
ASD  63  86  65  85 /   0   0  10  30
MSY  71  84  71  84 /   0   0  10  30
GPT  66  86  68  84 /   0   0  10  40
PQL  63  85  66  85 /   0   0  10  40

&&

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

$$







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