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

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519
FXUS64 KLIX 250148
AFDLIX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
848 PM CDT TUE MAR 24 2015

.SOUNDING DISCUSSION...
THERE WERE NO PROBLEMS WITH THE UPPER AIR RELEASE THIS EVENING.
THE 00Z SOUNDING DEPICTED A DRY AND STABLE ATMOSPHERE. THE
PRECIPITABLE WATER VALUE WAS 0.84 INCH AND THERE WAS A STRONG
INVERSION LOCATED JUST BELOW 800 MB. SOME MOISTURE WAS PRESENT
BELOW THIS INVERSION...BUT VERY DRY AIR WAS LOCATED AT ALL LEVELS
ABOVE IT. LIGHT TO MODERATE SOUTHERLY FLOW WAS OBSERVED BELOW THE
INVERSION...WITH WEST SOUTHWEST WINDS ABOVE THE INVERSION. 11

&&

.PREV DISCUSSION... /ISSUED 339 PM CDT TUE MAR 24 2015/

SHORT TERM...

A PERSISTENT THERMAL TROUGH AROUND 850MB HAS KEPT AN ELEVATED
INVERSION IN PLACE THROUGH DAY. AFTER REVIEWING MODEL SOUNDINGS
AND THE 850MB TEMPERATURE PLOT FROM SEVERAL MODEL SOURCES...HAVE
DECIDED TO KEEP A BROKEN STRATUS DECK IN PLACE FOR THE AREA
THROUGH TOMORROW AS THIS THERMAL TROUGH REMAINS IN PLACE.
TEMPERATURES WILL FINALLY WARM AND THE INVERSION WILL BEGIN TO
BREAK HEADING INTO TOMORROW NIGHT. THIS WILL MAINLY BE DUE TO
INCREASED SOUTHWEST FLOW IN THE MID-LEVELS PUMPING WARMER OFFSHORE
AIR INTO THE AREA. THERE MAY BE SOME PATCHY FOG DEVELOPING LATER
TONIGHT AS A WEAK LOW LEVEL INVERSION FORMS. HOWEVER...THE CLOUD
COVER IN PLACE WILL LIMIT THE STRENGTH OF RADIATIONAL
COOLING...LIMITING THE DEPTH OF THE INVERSION...AND THUS LOWERING
THE OVERALL RISK OF FOG. TEMPERATURES WILL REMAIN SEASONABLY
WARM...WITH READINGS IN THE MIDDLE TO UPPER 70S IN THE AFTERNOON
AND OVERNIGHT LOWS IN THE 50S AND LOWER 60S.

THURSDAY STILL LOOKS LIKE A VERY ACTIVE WEATHER DAY AS A POTENT
COLD FRONT SWEEPS THROUGH THE FORECAST AREA. EXPECT TO SEE A BAND
OF SHOWERS AND THUNDERSTORMS APPROACH THE AREA FROM THE NORTHWEST
TUESDAY MORNING...AND THEN QUICKLY RACE ACROSS ALL OF SOUTHEAST
LOUISIANA AND SOUTHERN MISSISSIPPI THURSDAY AFTERNOON INTO THE
EVENING. BY LATE EVENING...THE MAJORITY OF THE PRECIPITATION
SHOULD BE OFFSHORE...WITH ONLY SOME LINGERING SHOWERS EXPECTED
OVER FAR SOUTHEAST LOUISIANA. THERE WILL BE AMPLE OMEGA IN PLACE
AHEAD OF THE FRONT TO SUPPORT SOME STRONGER VERTICAL
UPDRAFTS...BUT OVERALL SHEAR VALUES LOOK TO BE VERY LIMITED AS THE
FRONT MOVES THROUGH. GIVEN THE LACK OF SHEAR...DO NOT EXPECT TO
SEE SEVERE THUNDERSTORM ACTIVITY FORM ALONG THE FRONT ON THURSDAY.
AT MOST...A FEW STRONGER CELLS COULD DEVELOP...PRODUCING FREQUENT
LIGHTNING STRIKES...GUSTY WINDS...AND HEAVY DOWNPOURS AS THEY MOVE
THROUGH.

STRONG DRY AND COLD AIR ADVECTION IN THE WAKE OF THE FRONT...ALONG
WITH INCREASING SUBSIDENCE THROUGHOUT THE ATMOSPHERIC COLUMN WILL
BRING RAPIDLY CLEARING SKIES AND RAPIDLY FALLING TEMPERATURES TO
THE AREA THURSDAY NIGHT. OVERNIGHT LOWS WILL DROP INTO THE 40S AND
LOWER 50S ACROSS THE REGION...ABOUT A 15 DEGREE DROP FROM
WEDNESDAY NIGHT. THE HEART OF THE COLD POOL WILL SETTLE IN ON
FRIDAY AND LINGER INTO SATURDAY...WITH TEMPERATURES AVERAGING
AROUND 10 DEGREES BELOW NORMAL. OVERNIGHT LOWS COULD FALL INTO THE
UPPER 30S OVER PARTS OF SOUTHWEST MISSISSIPPI SATURDAY MORNING.
WITH A DRY AND STABLE AIRMASS IN PLACE...CLEAR SKIES WILL BE RULE
FOR BOTH FRIDAY AND SATURDAY.

LONG TERM...

THE TROUGH DOMINATING THE EASTERN SEABOARD WILL BEGIN TO LIFT OUT
ON SUNDAY...AND EXPECT TO SEE A LARGELY ZONAL FLOW PATTERN SET UP
BY MONDAY. AS THE TROUGH DEPARTS...THE COLD POOL WILL ALSO PULL
AWAY FROM THE AREA. TEMPERATURES WILL SLOWLY MODIFY...WITH HIGHS
CLIMBING CLOSER TO 70 DEGREES ON SUNDAY...AND THEN WARMING BACK TO
MORE SEASONAL NORMS ON MONDAY. OVERNIGHT LOWS WILL REMAIN
COOL...IN THE UPPER 40S AND 50S SUNDAY NIGHT. TEMPERATURES WILL
CONTINUE TO WARM INTO MONDAY NIGHT...WITH LOWS CLOSER TO AVERAGE
IN THE MIDDLE TO UPPER 50S.

BOTH THE EURO AND GFS INDICATE THAT A SOUTHERN STREAM SHORT WAVE
TROUGH WILL BEGIN TO APPROACH THE AREA ON TUESDAY...BUT THERE ARE
SIGNIFICANT DIFFERENCES IN THE STRENGTH OF THIS FEATURE. THE GFS
HAS A MUCH DEEPER UPPER LEVEL LOW MOVING INTO THE SOUTHERN
PLAINS...WHILE THE EURO HAS A MUCH WEAKER AND OPEN TROUGH MOVING
INTO TEXAS. GIVEN THESE DIFFERENCES IN STRENGTH...HAVE WENT WITH A
BLEND OF SOLUTIONS IN THE DAY 7 AND 8 PERIOD. EXPECT TO SEE WARMER
AND MORE HUMID CONDITIONS MOVE IN TUESDAY AND DEEP LAYER SOUTHERLY
FLOW TAKES HOLD...AND A SLIGHT CHANCE OF RAIN MOVING IN FOR
WEDNESDAY AS THE TROUGH AXIS SLIDES THROUGH THE LOWER MISSISSIPPI
VALLEY.

AVIATION...

RATHER EXTENSIVE CUMULUS/STRATOCUMULUS FIELD DEVELOPED ON THE LOW
LEVEL ONSHORE FLOW THIS MORNING. TWO DIFFERENT LAYERS OF
CLOUDS...ONE THIN BAND TRAPPED JUST BELOW THE INVERSION AT 850
MB...AND SOME LOWER CLOUDS GENERALLY AROUND 2500 FEET. WHILE MOST
AREAS WILL REMAIN VFR FOR THE REMAINDER OF THE DAY...COULD SEE
OCCASIONAL BROKEN CLOUDS WITH THE 2500 FOOT LAYER PROVIDING MVFR
CONDITIONS. WE SHOULD LOSE AT LEAST SOME OF THE CLOUDS AFTER
SUNSET...BUT MODEL SOUNDINGS DO SHOW THAT MOISTURE FURTHER BELOW THE
850 MB INVERSION...CURRENTLY BEING OBSERVED NEAR 2500 FEET...COULD
BUILD DOWN ENOUGH TO CREATE CEILINGS BETWEEN 1500-2000 FEET
OVERNIGHT. TWO SCENARIOS EXIST...ONE WOULD BE FOR THE 1500-2000 FOOT
CEILINGS TO PREVAIL...THE OTHER WOULD BE FOR SKIES TO CLEAR
OVERNIGHT...PRODUCING THE POTENTIAL FOR RADIATION FOG AT MOST
TERMINALS. FOR THE MOST PART...THIS FORECAST PACKAGE TRENDS TOWARD
THE FIRST SCENARIO...WITH POTENTIAL FOR VFR CONDITIONS AT ALL
TERMINALS AROUND 15-16Z TOMORROW. 35

MARINE...

BENIGN CONDITIONS ARE EXPECTED OVER THE COASTAL WATERS THROUGH
THURSDAY...WITH WINDS OF 5 TO 10 KNOTS FROM THE SOUTH OVER THIS
PERIOD. THURSDAY NIGHT WILL BE A PERIOD OF TRANSITION AS A STRONG
COLD FRONT SWEEPS THROUGH THE COASTAL WATERS. AS A RESULT...A PERIOD
OF SMALL CRAFT ADVISORY CONDITIONS ARE EXPECTED TO FORM OVER SOME OR
MOST OF  THE COASTAL WATERS FRIDAY INTO FRIDAY NIGHT. WINDS WILL
SWITCH AROUND FROM NORTHEAST SATURDAY MORNING TO SOUTHEAST BY THE
EVENING AS SURFACE RIDGE TO THE NORTH SLIDES EAST. WINDS WILL REMAIN
ONSHORE SUNDAY AS THE HIGH BUILDS INTO THE NORTHEASTERN GULF OF
MEXICO. A BACKDOOR COLD FRONT MAY APPROACH THE COASTAL WATERS EARLY
NEXT WEEK BUT COULD BE IN A WEAKENING STATE AND HAVE LITTLE IMPACT.

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 TONIGHT RISK SVR
         AND/OR DIRECT TROPICAL THREATS; EVENTS OF NATIONAL
         SIGNIFICANCE

&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  77  52  79  56 /   0   0  10  10
BTR  78  53  80  57 /   0   0   0  10
ASD  77  53  79  57 /  10   0  10  10
MSY  76  58  79  62 /  10   0  10  10
GPT  75  56  77  59 /  10  10  10  10
PQL  76  54  78  56 /  10  10  10  10

&&

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

$$



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