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

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FXUS64 KLIX 221028
AFDLIX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
428 AM CST SAT NOV 22 2014

.DISCUSSION...
THE MAIN CONCERN DURING THE FORECAST PERIOD IS THE POTENTIAL FOR
SEVERE WEATHER LATE TONIGHT INTO SUNDAY MORNING ACROSS THE ENTIRE
FORECAST AREA. THERE HAVE BEEN A FEW CHANGES MADE TO THE FORECAST
IN REGARDS TO TIMING AND THE OUTLOOK BY THE STORM PREDICTION
CENTER. THE STORM PREDICTION UPGRADED THE SEVERE WEATHER OUTLOOK
TO AN ENHANCED THREAT OVER OUR AREA FOR LATE SATURDAY NIGHT INTO
THE EARLY MORNING HOURS SUNDAY. THE LATEST GUIDANCE STILL SHOWS
THE SLOWING TREND IN THE FORECAST AND DOES NOT REALLY GET
WIDESPREAD PRECIPITATION UNTIL AFTER MIDNIGHT TONIGHT WITH THE
HIGHEST CHANCE OF SEVERE WEATHER BEING BETWEEN MIDNIGHT SATURDAY
NIGHT THOUGH AT LEAST THE MID MORNING HOURS ON SUNDAY. HAVE
ADJUSTED POPS TO REFLECT THE NEW TIMING AND THREAT TO THE FORECAST
AREA.

DIGGING INTO SOME OF THE PARAMETERS AND SOUNDINGS THERE ARE A FEW
ALARMING THINGS THAT SHOW UP IN THE DATA. MOISTURE WILL NOT BE A
PROBLEM AS PRECIPITABLE WATER VALUES WILL BE APPROACHING 2 INCHES
SATURDAY NIGHT AND SUNDAY MORNING. THE KINEMATICS AND LIFT WILL BE
PLENTIFUL AS SHEAR AND DIFFLUENCE ALOFT WILL BE ABLE TO SUPPORT
SEVERE THUNDERSTORMS. THE FEW THINGS THAT ARE ALARMING COME TO
LIGHT AS YOU LOOK AT THE MODEL SOUNDINGS. THE GFS IS MORE OMINOUS
THAN THE NAM. THE GFSBUFR SOUNDINGS SHOW VERY HIGH 0-3KM HELICITY
VALUES APPROACHING THE 400 M2/S2 BY 9Z SUNDAY MORNING WITH CAPE
VALUES OF 1600 J/KG AT KMSY. THE SAME VALUES ARE ALSO DEPICTED AT
KASD...AND ALSO FOR KGPT BY 12Z. IF THESE VALUES WERE TO VERIFY
THERE COULD BE SOME DANGEROUS STORMS ONGOING IN THE WEE HOURS OF
SUNDAY MORNING. THE NAM IS SLOWER AND NOT AS STRONG AND DOES NOT
PAINT THE SAME PICTURE. THE NAM PARAMETERS KEEP THE HIGHEST VALUES
OUT OVER THE GULF AND THE ECMWF SEEMS TO BE SOMEWHERE IN THE
MIDDLE OF BOTH SOLUTIONS. OF COURSE WE WILL HAVE TO SEE WHAT
HAPPENS TODAY AND SEE HOW WELL THE ATMOSPHERE RECOVERS AND THE
TRACK OF THE SURFACE LOW AND TROUGH WILL GREATLY HAVE A INFLUENCE
ON THE SEVERITY AND PLACEMENT OF THE STRONGEST STORMS AND SQUALL
LINE. THE SAME LIMITING FACTORS THAT WERE DISCUSSED IN THE
PREVIOUS FORECAST EXIST. THE MAIN ONE THAT I SEE THAT COULD
HAPPENING IS ANY CONVECTION OUT OVER THE COASTAL WATERS COULD
LIMIT THE INFLOW AND DAMPEN THE ATMOSPHERE OVER THE LAND. SO THIS
WILL DEFINITELY HAVE TO BE WATCHED THROUGHOUT THE DAY AND INTO THE
EVENING TO SEE HOW THIS EVOLVES.

WE ARE STILL EXPECTING THE MAIN MODE OF SEVERE WEATHER TO COME IN
THE FORM OF A SQUALL LINE TONIGHT WITH DAMAGING STRAIGHT LINE
WINDS. WITH THE ATMOSPHERIC CONDITIONS THAT COULD BE IN PLACE OVER
THE AREA ANY STORMS THAT FORM AHEAD OF THE LINE WILL HAVE THE
GREATEST CHANCE FOR PRODUCING TORNADOES. THERE ALSO IS A HEAVY
RAIN THREAT WITH THIS SYSTEM. WE ARE STILL THINKING THAT 2 TO 3
INCHES OF RAIN COULD FALL OVER THE ENTIRE EVENT AND WITH THE AREA
BEING FAIRLY DRY WE ARE NOT ANTICIPATING WIDESPREAD FLASH FLOODING
PROBLEMS. HOWEVER WITH THE AMOUNT OF MOISTURE IN THE ATMOSPHERE
AND HIGH RAINFALL RATES POSSIBLE E COULD SEE SOME NUISANCE
TYPE STREET FLOODING OR POUNDING OF WATER IN LOW LYING AND POOR
DRAINAGE AREAS. HAVE DECIDED NOT TO ISSUE A FLASH FLOOD WATCH BUT
WILL LET THE DAY SHIFT HAVE THE FINAL DECISION WITH THAT.

LAST HAZARD TO TALK ABOUT WITH THIS EVENT IS THE COASTAL FLOOD
THREAT. PERSISTENT MODERATE TO STRONG ONSHORE FLOW HAS ALREADY
RESULTED IN TIDAL RISES ON EAST FACING SHORES. THIS TREND SHOULD
CONTINUE THROUGH TONIGHT AND SOME MINOR/NUISANCE COASTAL FLOODING
WILL BE POSSIBLE OUTSIDE OF LEVEE PROTECTION FOR AREAS FROM BAY
SAINT LOUIS TO THE MOUTH OF THE MISSISSIPPI RIVER. A COASTAL FLOOD
ADVISORY IS IN EFFECT FOR THESE AREAS FROM NOON TODAY THROUGH 6 AM
SUNDAY.

CONDITIONS SHOULD IMPROVE RAPIDLY FROM WEST TO EAST BY MID TO LATE
MORNING ACROSS THE AREA AND NO CHANGES WERE REALLY MADE AFTER
MONDAY WITH THE CURRENT FORECAST. THE COLD FRONT FINALLY SWINGS
THROUGH THE AREA SUNDAY NIGHT BRINGING COOLER AND DRIER AIR WITH
IT. A REINFORCING FRONT IS FORECAST TO MOVE THROUGH THE AREA
TUESDAY NIGHT...BUT WITH VERY LITTLE MOISTURE IN PLACE...EXPECT IT
TO COME THROUGH DRY.

WITH ALL OF THAT BEING SAID...THE MAIN TAKE AWAY SHOULD BE PLEASE
STAY ABREAST OF THE WEATHER SITUATION FOR LATER ON THIS EVENING
AND OVERNIGHT HOURS. THE GREATEST WINDOW FOR SEVERE WEATHER WILL
BE AFTER MIDNIGHT TONIGHT THROUGH SUNDAY MORNING. CHECK OUR SOCIAL
MEDIA PAGES AND OUR MAIN WEBSITE FOR THE LATEST TODAY IN REGARDS
TO THE SEVERE WEATHER THREAT TONIGHT. 13/MH

&&

.AVIATION...
SIMILAR TO LAST NIGHT VFR CONDITIONS WILL PERSIST
THROUGH THE FCST. ONLY ISSUE AT THIS TIME WOULD BE TEMPO MVFR VSBYS
DUE TO FOG AT THE NORMAL PROBLEM SITES...MCB/ASD/GPT/HDC. /CAB/

&&

.MARINE...
MULTIPLE IMPACTS EXPECTED OVER THE COASTAL WATER LIKELY
THROUGH THE NEXT 4-5 DAYS. AS HAS BEEN MENTIONED THE LAST FEW DAYS A
VERY STRONG LATE FALL STORM SYSTEM WILL BRING A MULTITUDE OF ISSUES
TO THE REGION WITH SOME BEGINNING AS EARLY AS TODAY. DEVELOPING SFC
LOW IN TX AND STRONG HIGH CNTRD OVER THE TOBACCO ROAD REGION WILL
LEAD TO A TIGHTENING OF THE PRESSURE GRADIENT WITH ERLY FLOW PICKING
UP TO AROUND AROUND 15-20 KTS BY MIDDAY OVER THE OPEN WATERS WITH
FREQUENT GUSTS LIKELY ABV 20 KTS. WITH THAT WE WILL ISSUE A SCY
BEGINNING AT 18Z TODAY AND HAVE IT RUN THROUGH AT LEAST 12Z SUN.
THIS WILL LIKELY NEED TO BE EXTENDED OR AT LEAST REISSUED LATE
SUN/MON. THE SCY WILL EXPAND AT 12Z SAT TO INCLUDE THE TIDAL LAKES
AND SOUNDS. THE STRONG WIND AND PERSISTENT ERLY TO SERLY FLOW TODAY
THROUGH SUN MORNING WILL LEAD TO WATER PILING UP ON THE COAST. WITH
THAT A COASTAL FLOOD ADV HAS ALREADY BEEN ISSUED AND NO CHANGES WILL
BE MADE TO IT. LAST OF COURSE WILL BE CONVECTION THAT WILL LIKELY
BEGIN TO IMPACT THE REGION SAT AFTN WITH A SQUALL LINE ANTICIPATED
OVERNIGHT SAT AND EARLY SUN MORNING. /CAB/

&&

.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  71  60  77  53 /  50 100 100  10
BTR  73  63  78  55 /  60 100 100  10
ASD  72  63  78  58 /  50 100 100  10
MSY  73  65  78  60 /  60 100 100  10
GPT  69  64  76  60 /  50 100 100  10
PQL  69  63  76  60 /  50 100 100  10

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...COASTAL FLOOD ADVISORY FROM NOON SATURDAY TO 6 AM SUNDAY FOR THE
     FOLLOWING ZONES: LOWER PLAQUEMINES...LOWER ST.
     BERNARD...ORLEANS...AND UPPER ST. BERNARD.

GM...SMALL CRAFT ADVISORY UNTIL 6 PM SUNDAY FOR THE FOLLOWING ZONES:
     BRETON SOUND...CHANDELEUR SOUND...LAKE BORGNE...LAKE
     PONTCHARTRAIN AND LAKE MAUREPAS...AND MISSISSIPPI SOUND.

     SMALL CRAFT ADVISORY UNTIL 6 PM 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 PORT FOURCHON
     TO LOWER ATCHAFALAYA RIVER OUT 20 NM...COASTAL WATERS FROM
     STAKE ISLAND LA TO THE SOUTHWEST PASS OF THE MISSISSIPPI
     RIVER FROM 20 TO 60 NM...COASTAL WATERS FROM THE SOUTHWEST
     PASS OF THE MISSISSIPPI RIVER TO PORT FOURCHON FROM 20 TO
     60 NM...AND COASTAL WATERS FROM THE SOUTHWEST PASS OF THE
     MISSISSIPPI RIVER TO PORT FOURCHON OUT 20 NM.

MS...COASTAL FLOOD ADVISORY FROM NOON SATURDAY TO 6 AM SUNDAY FOR THE
     FOLLOWING ZONES: AND HANCOCK.

GM...SMALL CRAFT ADVISORY UNTIL 6 PM SUNDAY FOR THE FOLLOWING ZONES:
     BRETON SOUND...CHANDELEUR SOUND...LAKE BORGNE...LAKE
     PONTCHARTRAIN AND LAKE MAUREPAS...AND MISSISSIPPI SOUND.

     SMALL CRAFT ADVISORY UNTIL 6 PM 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 PORT FOURCHON
     TO LOWER ATCHAFALAYA RIVER OUT 20 NM...COASTAL WATERS FROM
     STAKE ISLAND LA TO THE SOUTHWEST PASS OF THE MISSISSIPPI
     RIVER FROM 20 TO 60 NM...COASTAL WATERS FROM THE SOUTHWEST
     PASS OF THE MISSISSIPPI RIVER TO PORT FOURCHON FROM 20 TO
     60 NM...AND COASTAL WATERS FROM THE SOUTHWEST PASS OF THE
     MISSISSIPPI RIVER TO PORT FOURCHON OUT 20 NM.

&&

$$







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