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

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38
158
FXUS64 KLIX 221839
AFDLIX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
1239 PM CST SAT NOV 22 2014

.AVIATION...
CONDITIONS ARE GRADUALLY EXPECTED TO DETERIORATE TO MVFR TO IFR
BY THIS AFTERNOON INTO TONIGHT AND SUNDAY MORNING AS A STORM
SYSTEM APPROACHES THE AREA. RAIN AND THUNDERSTORMS ARE EXPECTED TO
BECOME WIDESPREAD OVER THE AIRPORTS ALONG AND WEST OF I-55
BETWEEN 06Z-12Z SUNDAY AND ELSEWHERE BETWEEN 10Z-16Z. STRONG TO
SEVERE TSRA MAY BECOME WIDESPREAD AND ORGANIZED ENOUGH TO HAVE A
HIGH PROBABILITY OF GUSTS 35 TO 40 KNOTS AS A SQUALL LINES MOVES
THROUGH...SO HAVE ADDED A 4 HOUR TEMPO GROUP WITH THESE GUSTS
ALONG WITH LOWER VSBYS AND CIGS DURING THE PERIOD OF TSRA. 22/TD

&&

.PREV DISCUSSION... /ISSUED 837 AM CST SAT NOV 22 2014/

UPDATE...
QUICK UPDATE TO THE ZONES MAINLY TO ELIMINATE THE HIGHER POPS
THAT BLED OVER INTO THE LATE AFTERNOON PERIOD FROM THE EVENING
PERIOD. HAVE REDUCED POPS GENERALLY TO THE 20 TO 30 PERCENT
RANGE FOR THIS AFTERNOON OVER LAND AREAS...AND FRANKLY EVEN THAT
MIGHT BE GENEROUS BASED ON LATEST GUIDANCE. ALSO MADE SOME MINOR
ADJUSTMENTS TO HOURLY TEMPERATURES TO CAPTURE LATEST OBSERVATION
TRENDS.

OTHERWISE...FORECAST LOOKS TO BE ON TRACK AND NO ADDITIONAL
UPDATES ARE ANTICIPATED BEFORE THIS AFTERNOON/S PACKAGE.

PREV DISCUSSION... /ISSUED 458 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.

MARINE...
WINDY CONDITIONS OVER ALL OF THE WATERS. A DEEPENING SFC
LOW WILL MOVE FROM ERN TX THROUGH THE ARKLAMISS AND INTO WRN
TENNESSEE. THIS WILL KEEP THE WINDS STRONG THROUGH SUN WITH ONSHORE
FLOW. THE PERSISTENT STRONG ONSHORE FLOW WILL ALSO LEAD TO HIGHER
THAN NORMAL TIDES BEGINNING LATER TODAY. NUMEROUS SHOWERS AND
THUNDERSTORMS WILL ALSO IMPACT THE MARINE ZONES LATE TODAY AND
THROUGH SUN MORNING UNTIL A SQUALL LINE MOVES THROUGH. A COLD FRONT
WILL FINALLY MOVE THROUGH LATE MON BUT AS THIS HAPPENS WINDS WILL
GET ANOTHER SURGE BACK INTO SCY CRITERIA. MODERATE TO STRONG
OFFSHORE WILL REMAIN OVER THE REGION TUE THROUGH MUCH OF NEXT WEEK.

AVIATION...
TAFS WILL REMAIN QUIET THROUGH AT LEAST THE FIRST HALF
OF THE DAY AND POSSIBLY THROUGH 0Z. BY THAT TIME THOUGH CONVECTION
WILL BEGIN TO ROLL INTO THE REGION AND TAFS WILL BEGIN TO HEAD
DOWNHILL THROUGH THE NIGHT.

DECISION SUPPORT...
DSS CODE...BLUE.
DEPLOYED...NONE.
ACTIVATION...NONE.
ACTIVITIES...SLURRY SUPPORT
             SMALL CRAFT ADVISORIES
             COASTAL FLOOD ADVISORY
             ENHANCED RISK OF SEVERE

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 /  20  90 100  10
BTR  73  63  78  55 /  30 100  90  10
ASD  72  63  78  58 /  30  90 100  10
MSY  73  65  78  60 /  30  90 100  10
GPT  69  64  76  60 /  20  80 100  10
PQL  69  63  76  60 /  20  70 100  10

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...COASTAL FLOOD ADVISORY UNTIL 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...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...COASTAL WATERS FROM THE SOUTHWEST PASS OF THE
     MISSISSIPPI RIVER TO PORT FOURCHON OUT 20 NM...LAKE
     BORGNE...LAKE PONTCHARTRAIN AND LAKE MAUREPAS...AND
     MISSISSIPPI SOUND.

MS...COASTAL FLOOD ADVISORY UNTIL 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...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...COASTAL WATERS FROM THE SOUTHWEST PASS OF THE
     MISSISSIPPI RIVER TO PORT FOURCHON OUT 20 NM...LAKE
     BORGNE...LAKE PONTCHARTRAIN AND LAKE MAUREPAS...AND
     MISSISSIPPI SOUND.

&&

$$







USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.