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

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117
FXUS64 KLIX 280321
AFDLIX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
921 PM CST FRI FEB 27 2015

.UPDATE...

UPDATED MARINE HEADLINES TO BETTER FIT WIND FORECAST DESCRIBED IN
GRIDS. THIS WILL ADD INNER OPEN WATERS EAST OF THE MOUTH OF THE
MISSISSIPPI RIVER TO THE ADVISORY...AND WILL CARRY EXERCISE
CAUTION ACROSS REMAINING MARINE ZONES.

WILL ALSO MASSAGE HOURLY TEMP/DEW POINT GRIDS TO FIT EXISTING
CONDITIONS. NO CHANGES TO OVERNIGHT LOW FORECAST AT THIS TIME. 35

&&

.PREV DISCUSSION... /ISSUED 723 PM CST FRI FEB 27 2015/

SOUNDING DISCUSSION...

ROUTINE FLIGHT TERMINATED A FEW MILES FROM LAST NIGHTS TERMINATION
POINT...ABOUT 2 MILES NORTH OF THE UNIVERSITY OF SOUTH ALABAMA
CAMPUS IN MOBILE. FLIGHT REACHED A HEIGHT OF 110.5K FEET OR CLOSE
TO 21 MILES IN ALTITUDE AFTER 105 MINUTES OF FLIGHT.

SOUNDING REMAINS RATHER DRY WITH A PRECIPITABLE WATER VALUE OF
0.49 INCHES. THERE WAS ABOUT A 4C INVERSION JUST BELOW 900
MB...AND AN ISOTHERMAL LAYER BETWEEN 780 AND 680 MB. FREEZING
LEVEL WAS AT 11K FEET...AND -20C WAS AT 21.6 FEET.

WINDS WERE LIGHT NORTHERLY IN THE LOWEST 5000 FEET...BECAME
WESTERLY AROUND 7000 FEET AND REMAINED GENERALLY WESTERLY THROUGH
100 MB. MAX WIND OF 120 KNOTS AT 36.8K FEET.  35

PREV DISCUSSION... /ISSUED 250 PM CST FRI FEB 27 2015/

SHORT TERM...
CLEAR SKIES CONTINUE OVER THE AREA THIS AFTERNOON AS STRONG HIGH
PRESSURE BUILDS IN FROM THE NORTH. TEMPERATURES HAVE STRUGGLED TO
REACH THE LOWER 50S AND A FEW LOCATIONS HAVEN/T EVEN DONE THAT AS
COLD AIR ADVECTION BRINGS IN THE SURGE OF COLD AIR. SIMILAR TREND
WILL PERSIST OVERNIGHT WITH ANOTHER ROUND OF SUB 40 DEGREE LOWS AND
POSSIBLY A FEW LOCATIONS TOUCHING FREEZING ONCE AGAIN. TEMPS COULD
BE EVEN COLDER THAN THAT BUT GUIDANCE SHOWING MIDLEVEL MOISTURE
INCREASING THIS EVENING AND OVERNIGHT WHICH SHOULD RESULT IN SOME
CLOUDS AT AROUND 10K FEET. THINKING IS THAT THIS WILL KEEP TEMPS
FROM FALLING TOO MUCH. FOR CLIMATOLOGY REFERENCE...THESE
TEMPERATURES ARE STILL AROUND 15 TO 20 DEGREES BELOW NORMAL.
CONDITIONS WILL NOT BE ALL THAT DIFFERENT TOMORROW EXCEPT FOR TEMPS
ABOUT 10 DEGREES WARMER MOISTURE ON THE RISE AS WINDS BECOME MORE
EASTERLY.

LONG TERM...
SIGNIFICANT CHANGES WILL BE COMING THIS WEEKEND. UPPER LEVEL RIDGE
WILL BE BUILDING OVER THE CARIBBEAN/GULF OF MEXICO AND PUSHING NORTH
INTO GULF COAST. THIS WILL BRING MOISTURE AND WARMER TEMPS TO THE
AREA BEGINNING SUNDAY. HIGHS WILL BE COMING UP INTO THE MID TO UPPER
60S SUNDAY PER GUIDANCE. RAIN CHANCE IS SLIGHTLY MORE UNCERTAIN ON
SUNDAY AS GFS HAS BACKED OFF BY 20 TO 30 PERCENT. DID LOWER POPS
SOME BUT NOT TO THAT DEGREE AS ECMWF STILL SHOWING QUITE A BIT OF
ACTIVITY OVER THE AREA.

MODELS STILL SHOWING A COLD FRONT APPROACHING THE AREA MONDAY BUT
STALLING TO THE NORTH DUE TO LOSS OF ITS UPPER LEVEL TROUGH PUSH.
RAIN CHANCES DO REMAIN ELEVATE WITH NORTHERN ZONES SEEING HIGHER
POPS THAN COASTAL AREAS. NO BIG CHANGES FROM PREVIOUS FORECAST FOR
THAT OR TEMPS. KEPT HIGHS IN THE LOWER TO MID 70S AS WELL AS
DEWPOINTS IN THE 60S. WILL THEN BE IN A LULL FOR RAIN TUESDAY...
THOUGH A FEW SCATTERED SHOWERS POSSIBLE...UNTIL THE NEXT FRONT COMES
ON WEDNESDAY. THE UPPER LEVEL TROUGH BEHIND THIS FRONT LOOKS BE MUCH
BROADER AND WILL DIG FURTHER SOUTH ACROSS THE SERN CONUS. COULD SEE
A GOOD 24 HOUR PERIOD OF LIGHT TO MODERATE RAIN. LATEST MODEL
SOUNDING INDICATE THAT SUB FREEZING LOW LEVEL AIR COULD PUSH IN OVER
SOUTHERN MISSISSIPPI RIGHT BEFORE THE RAIN FINISHES. IF THIS WERE TO
HAPPEN...A SHORT PERIOD OF FREEZING RAIN MIXED WITH SLEET COULD
OCCUR. TOO MANY IF`S AT THIS TIME TO BE OVERLY CONCERNED WITH THAT
OUTCOME AT THIS TIME. JUST SOMETHING TO WATCH.

MEFFER

AVIATION...

LOW CLOUDS WITH BASES 016-022 SHOULD DISSIPATE BY OR SHORTLY AFTER
THE START OF THE 18Z TAF PERIOD. GENERALLY CLEAR SKIES AND EXCELLENT
VSBYS WILL PREVAIL THROUGH THIS EVENING. SLIGHTLY ELEVATED NORTHEAST
WINDS 10 TO 15 KNOTS WITH A FEW GUSTS TO NEAR 20 KNOTS SHOULD
SUBSIDE EARLY THIS AFTERNOON. SOME MID LEVEL CLOUDS ARE EXPECTED
TONIGHT...AND THIS WILL LIKELY KEEP TEMPERATURES FROM FALLING CLOSE
ENOUGH TO THE DEWPOINTS TO PRODUCE FOG OR MIST...SO VFR IS EXPECTED
TO PREVAIL THROUGH 18Z SATURDAY.

22/TD

MARINE...
A REINFORCING SHOT OF COLD AIR WILL CONTINUE TO SETTLE IN OVER THE
FORECAST AREA TONIGHT. THE PRESSURE GRADIENT DIDN/T REALLY
RELAX...SO HAD TO EXTEND THE SCA TO THIS AFTERNOON WITH THIS
MORNING/S ISSUANCE. NOW...WITH NOCTURNAL WIND ENHANCEMENT EXPECTED
OVER OFFSHORE WATERS...DOESN/T MAKE SENSE TO CANCEL THE SCA FOR A
SHORT PERIOD LATE THIS AFTERNOON BEFORE WINDS PICK BACK UP TO ABOVE
20 KNOTS. KIND OF IN THE SAME BOAT TOMORROW AS WINDS MAY SLIGHTLY
WEAKEN DURING THE DAY TO JUST BELOW CRITERIA AND THEN COME BACK UP
IN THE EVENING. WINDS WILL FINALLY SWITCH AROUND TO THE EAST ON
SUNDAY AND THEN SOUTHEAST MONDAY AND TUESDAY AS HIGH PRESSURE TO THE
NORTH...SLIDES EAST. FORECASTED MID TO UPPER 60 DEGREE DEWPOINTS
WILL BE CONDUCIVE FOR SEA FOG DEVELOPMENT NEXT WEEK. STRONG COLD
FRONT TO BRING THE RETURN OF SCA CONDITIONS LATER ON WEDNESDAY.

MEFFER

DECISION SUPPORT...

DSS CODE...BLUE.
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  32  61  47  66 /  10  10  10  40
BTR  34  61  50  70 /  10  10  20  40
ASD  36  60  50  67 /  10  10  20  40
MSY  41  58  54  70 /  10  10  20  50
GPT  38  59  51  65 /  10  10  20  40
PQL  36  61  47  66 /  10  10  20  30

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...NONE.
GM...SMALL CRAFT ADVISORY UNTIL MIDNIGHT SUNDAY 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...COASTAL WATERS FROM PORT FOURCHON TO LOWER
     ATCHAFALAYA RIVER FROM 20 TO 60 NM...COASTAL WATERS FROM
     STAKE ISLAND LA TO THE SOUTHWEST PASS OF THE MISSISSIPPI
     RIVER FROM 20 TO 60 NM...AND COASTAL WATERS FROM THE
     SOUTHWEST PASS OF THE MISSISSIPPI RIVER TO PORT FOURCHON
     FROM 20 TO 60 NM.

MS...NONE.
GM...SMALL CRAFT ADVISORY UNTIL MIDNIGHT SUNDAY 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...COASTAL WATERS FROM PORT FOURCHON TO LOWER
     ATCHAFALAYA RIVER FROM 20 TO 60 NM...COASTAL WATERS FROM
     STAKE ISLAND LA TO THE SOUTHWEST PASS OF THE MISSISSIPPI
     RIVER FROM 20 TO 60 NM...AND COASTAL WATERS FROM THE
     SOUTHWEST PASS OF THE MISSISSIPPI RIVER TO PORT FOURCHON
     FROM 20 TO 60 NM.

&&

$$







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