Flash Flooding and Flooding in Louisiana, March 10 to 15, 2016

AREA FORECAST DISSCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
422 PM CST THU MAR 10 2016

.SHORT TERM...
AS ADVERTISED A LONG DURATION HEAVY RAINFALL EVENT IS FINALLY
UNDERWAY ACROSS OUR FORECAST AREA. NO MAJOR CHANGES IN THE
THINKING FROM THE LAST FORECAST PACKAGE. HEAVY RAIN IS ONGOING
ACROSS THE FORECAST AREA THIS AFTERNOON MAINLY ALONG AND WEST OF
INTERSTATE 55. BATON ROUGE HAS ALREADY MEASURED THREE INCHES OF
RAIN THIS AFTERNOON. THIS SYSTEM HAS A LOT GOING FOR IT AS IT
SLOWLY MOVES ACROSS THE AREA THROUGH SATURDAY. DEEP MOISTURE WILL
BE IN PLACE...PRECIPITABLE WATER VALUES WILL BE AT A RECORD HIGH
OVER THE NEXT FEW DAYS. THE MEASURED PRECIPITABLE WATER VALUE FROM
THIS MORNING WAS 1.76 INCHES AND THAT WAS A DAILY RECORD...AND I
EXPECT THE NEXT FEW OBSERVATIONS TO BE RECORDS AS WELL. MODELS
INDICATE THAT THE VALUES OVER THE NEXT 24 TO 48 HOURS WILL BE IN
THE 1.8 TO 2.1 INCH RANGE. THAT IS A SIGNIFICANT AMOUNT OF
MOISTURE FOR THIS TIME OF THE YEAR. WARM CLOUD DEPTHS ARE IN THE
12K TO 14K FOOT RANGE...COUPLE THAT WITH THE SLOW MOVING AND
TRAINING NATURE OF THE SHOWERS AND STORMS AND YOU HAVE A RECIPE
FOR FLOODING. THE WEATHER PREDICTION CENTER HAS OUR AREA IN A
MODERATE RISK FOR FLASH FLOODING TONIGHT THROUGH FRIDAY EVENING.
JUST LOOKING AT A FEW TRENDS OF HIGH RES GUIDANCE IT LOOKS AS IF
THIS CURRENT BAND OF RAIN WILL STALL OVER THE NEXT FEW HOURS AND
PIVOT TO MORE OF AN EAST/WEST ORIENTATION BEFORE AN ADDITIONAL BAND
DEVELOPS OVERNIGHT AND MOVES IN BY DAYBREAK. I AM BECOMING MORE
CONCERNED OVERNIGHT WITH THE DEVELOPMENT OF SOME DEEPER CONVECTION
EMBEDDED IN THE OVERALL BAND THAT WOULD GREATLY ENHANCE RAINFALL
TOTALS. THERE IS SOME ELEVATED CAPE THAT WILL BE IN PLACE TONIGHT
AND WITH THESE LITTLE IMPULSES IN THE MAIN FLOW THAT COULD
TRIGGER A FEW STORMS WITH HEAVIER RAIN.

THE SEVERE WEATHER TREAT IS SMALL BUT NON ZERO...WE STILL MAINTAIN
A MARGINAL RISK FOR SEVERE WEATHER TONIGHT WITH DAMAGING WINDS
BEING THE MAIN CONVECTIVE CONCERN OUTSIDE OF HEAVY RAINFALL. AN
ADDITIONAL 3 TO 4 INCHES OF RAIN WITH LOCALLY HIGHER AMOUNTS COULD
IMPACT AREAS WEST OF INTERSTATE 55...BRINGING RAIN TOTALS OT 7 TO
10 INCHES. FOR AREAS EAST OF THE I-55 CORRIDOR IN SOUTHEAST
LOUISIANA AND SOUTHWEST MISSISSIPPI...INCLUDING METRO NEW
ORLEANS...HEAVY RAINFALL OF 3 TO 6 INCHES WITH LOCALLY HIGHER
AMOUNTS OVER 8 INCHES COULD OCCUR TONIGHT AND TOMORROW. AS STATED
IN THE PREVIOUS PACKAGE THERE WAS SHIFT IN THINKING FOR
SATURDAY...AND THAT INDICATION HAS BEEN REINFORCED WITH MODEL
RUNS FOR TODAY. THE HEAVY RAIN THREAT WILL LINGER OVER THE
FORECAST AREA THROUGH SATURDAY AFTERNOON. IT LOOKS LIKE THE
HIGHEST PROBABILITY AREAS FOR HEAVY RAINFALL WILL GENERALLY BE
FROM METRO NEW ORLEANS AND THE NORTHSHORE EASTWARD ACROSS THE
MISSISSIPPI GULF COAST. AN ADDITIONAL 3 TO 5 INCHES OF RAIN WITH
LOCALLY HIGHER AMOUNTS OF OVER 6 INCHES COULD IMPACT METRO NEW
ORLEANS AND NORTHSHORE. THE MISSISSIPPI COAST COULD EASILY SEE 3
TO 5 INCHES OF RAIN AS WELL WITH LOCALLY HIGHER AMOUNTS OVER 6
INCHES POSSIBLE. STORM TOTAL RAINFALL ACROSS THE AREA COULD VARY
FROM 7 TO 10 INCHES FOR THE BATON ROUGE AREA AND MISSISSIPPI GULF
COAST TO A BULLSEYE OF 10 PLUS INCHES FOR METRO NEW ORLEANS AND
THE NORTHSHORE BY THE TIME THE EVENT IS OVER. ALL OF THESE TOTALS
ARE HIGHLY DEPENDENT ON EXACTLY WHERE THE HEAVY RAIN BAND
DEVELOPS...AND IF MULTIPLE AREAS OF HEAVIER RAIN TRAIN OVER THE
SAME LOCATION. SIGNIFICANT FLOODING ISSUES COULD ARISE WITH THIS
EVENT GIVEN THE HIGH RAINFALL TOTALS EXPECTED. 13/MH

.LONG TERM...
THE SYSTEM FINALLY MOVES OUT LATE SATURDAY INTO SUNDAY. ANOTHER
QUICK MOVING IMPULSE WILL MOVE NORTH OF THE AREA. NOT EXPECTING
ANY RAINFALL FROM THAT IMPULSE...SO WE WILL DRY OUT FOR THE
LATTER HALF OF THE WEEKEND. TEMPERATURES WILL WARM INTO THE 80S BY
EARLY NEXT WEEK. THE NEXT CHANCE OF ORGANIZED RAINFALL LOOKS TO
OCCUR IN THE WEDNESDAY THURSDAY TIMEFRAME. A FRONT IS EXPECTED TO
MOVE THROUGH AROUND THAT TIME AND SHOULD BE THE FOCUS FOR
SCATTERED SHOWER AND THUNDERSTORM ACTIVITY. TEMPERATURES WILL
REMAIN MILD...WITH HIGHS IN THE MIDDLE TO UPPER 70S BOTH WEDNESDAY
AND THURSDAY. AS MOISTURE INCREASES OVER THE AREA...OVERNIGHT LOWS
SHOULD CLIMB BACK INTO THE 60S BY WEDNESDAY NIGHT. 13/MH

&&

.AVIATION...
CONDITIONS WILL BE ROUGH THROUGH THE FCST. ALL TERMINALS WILL
LIKELY BE DEALING WITH PERSISTENT MVFR TO IFR CONDITIONS AND COULD
EVEN DROP TO LIFR DURING THE HEAVIER SHRA AND TSRA. WITH THE
EXCEPTION OF THE MS COAST ALL TERMINALS WILL BE DEALING WITH SOME
CONVECTION BY NO LATER THAN 2230Z. WINDS ARE FINALLY RELAXING SOME
SO NOT ANTICIPATING ANY LLWS ISSUES TOMORROW MORNING AROUND MSY
AND NEW. /CAB/

&&

.MARINE...
STRONG ONSHORE FLOW WILL CONTINUE INTO TOMORROW AS THE GRADIENT
RELAXES AND TIGHTENS BACK UP WITH EACH WAVE. SOUTHEAST WINDS WILL
CONTINUE TO RANGE FROM 15 TO 25 KTS AT TIMES. EVEN WHEN THE WINDS
DROP BELOW 20 KTS FREQUENT GUSTS OF GREATER THAN 25 KTS WILL BE
OCCURRING OVER PRETTY MUCH ALL OF THE COASTAL WATERS. SCY FLAGS
WILL REMAIN IN EFFECT THROUGH FRI AND WILL LIKELY NEED TO BE
EXTENDED INTO THE WEEKEND.

THE STRONG ONSHORE FLOW IS ALSO LEADING TO MINOR TO MODERATE COASTAL
FLOODING AND THIS WILL CONTINUE TO BE THE CASE THROUGH TOMORROW AS
WELL. THERE IS A CHANCE THAT TIDES COULD BOUNCE BACK TO 3.5 FT ABV
NORMAL IN ISOLATED AREAS FRI NIGHT AND SAT MORNING WHEN THE WINDS
LOOK TO INCREASE ONCE AGAIN AND THE ASTRONOMICAL TIDE RANGES RAMP
BACK UP. /CAB/

&&

.DECISION SUPPORT...
.DECISION SUPPORT...
DSS CODE....YELLOW.
DEPLOYED...NONE.
ACTIVATION...NONE.
ACTIVITIES...RIVER FLOODING
             FLASH FLOOD WATCH
             COASTAL FLOOD ADV
             SMALL CRAFT ADV

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

&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  68  72  65  72 / 100 100  80  90
BTR  68  73  65  74 / 100 100  80  80
ASD  69  73  67  73 / 100 100  90  90
MSY  69  73  67  74 / 100 100  90  90
GPT  68  73  67  72 / 100 100  90  90
PQL  68  73  66  72 / 100 100  90  90

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...FLASH FLOOD WATCH THROUGH SATURDAY AFTERNOON FOR LAZ034>037-039-
     040-046>050-056>072.

     COASTAL FLOOD ADVISORY UNTIL 6 PM CST FRIDAY FOR LAZ049-050-057-
     058-060>064-066>070.

     WIND ADVISORY UNTIL 6 PM CST THIS EVENING FOR LAZ040-058>070-072.

     COASTAL FLOOD WARNING UNTIL 6 PM CST THIS EVENING FOR LAZ040-072.

     COASTAL FLOOD ADVISORY FROM 6 PM THIS EVENING TO 6 PM CST FRIDAY
     FOR LAZ040-072.

GM...SMALL CRAFT ADVISORY UNTIL 6 PM CST FRIDAY FOR GMZ530-532-534-
     536-538-550-552-555-557-570-572-575-577.

MS...FLASH FLOOD WATCH THROUGH SATURDAY AFTERNOON FOR MSZ068>071-077-
     080>082.

     COASTAL FLOOD ADVISORY UNTIL 6 PM CST FRIDAY FOR MSZ081-082.

     WIND ADVISORY UNTIL 6 PM CST THIS EVENING FOR MSZ080>082.

     COASTAL FLOOD WARNING UNTIL 6 PM CST THIS EVENING FOR MSZ080.

     COASTAL FLOOD ADVISORY FROM 6 PM THIS EVENING TO 6 PM CST FRIDAY
     FOR MSZ080.

GM...SMALL CRAFT ADVISORY UNTIL 6 PM CST FRIDAY FOR GMZ532-534-536-
     538-550-552-555-557-570-572-575-577.

&&

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE NEW ORLEANS LA
600 PM CST THU MAR 10 2016

GMZ530-532-534-536-538-550-552-555-557-570-572-575-577-LAZ034>037-
039-040-046>050-056>072-MSZ068>071-077-080>082-111400-
LAKE PONTCHARTRAIN AND LAKE MAUREPAS-MISSISSIPPI SOUND-
LAKE BORGNE-CHANDELEUR SOUND-BRETON SOUND-
COASTAL WATERS FROM PORT FOURCHON LA TO LOWER ATCHAFALAYA RIVER
LA OUT 20 NM-
COASTAL WATERS FROM THE SOUTHWEST PASS OF THE MISSISSIPPI RIVER
TO PORT FOURCHON LOUISIANA OUT 20 NM-
COASTAL WATERS FROM BOOTHVILLE LA TO SOUTHWEST PASS OF THE
MISSISSIPPI RIVER OUT 20 NM-
COASTAL WATERS FROM PASCAGOULA MISSISSIPPI TO STAKE ISLAND OUT
20 NM-
COASTAL WATERS FROM PORT FOURCHON LOUISIANA TO LOWER ATCHAFALAYA
RIVER LA FROM 20 TO 60 NM-
COASTAL WATERS FROM SOUTHWEST PASS OF THE MISSISSIPPI RIVER TO
PORT FOURCHON LOUISIANA FROM 20 TO 60 NM-
COASTAL WATERS FROM STAKE ISLAND LA TO SOUTHWEST PASS OF THE
MISSISSIPPI RIVER FROM 20 TO 60 NM-
COASTAL WATERS FROM PASCAGOULA MISSISSIPPI TO STAKE ISLAND
LOUISIANA OUT 20 TO 60 NM-POINTE COUPEE-WEST FELICIANA-
EAST FELICIANA-ST. HELENA-WASHINGTON-ST. TAMMANY-IBERVILLE-
WEST BATON ROUGE-EAST BATON ROUGE-ASCENSION-LIVINGSTON-ASSUMPTION-
ST. JAMES-ST. JOHN THE BAPTIST-UPPER LAFOURCHE-ST. CHARLES-
UPPER JEFFERSON-ORLEANS-UPPER PLAQUEMINES-UPPER ST. BERNARD-
UPPER TERREBONNE-LOWER TERREBONNE-LOWER LAFOURCHE-LOWER JEFFERSON-
LOWER PLAQUEMINES-LOWER ST. BERNARD-NORTHERN TANGIPAHOA-
SOUTHERN TANGIPAHOA-WILKINSON-AMITE-PIKE-WALTHALL-PEARL RIVER-
HANCOCK-HARRISON-JACKSON-
600 PM CST THU MAR 10 2016

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTHEAST
LOUISIANA...SOUTH MISSISSIPPI AND THE ADJACENT COASTAL WATERS.

.DAY ONE...TONIGHT

SMALL CRAFT ADVISORIES REMAIN IN EFFECT FOR ALL THE COASTAL WATERS TONIGHT.

A COASTAL FLOOD ADVISORY IS IN EFFECT FOR ALL COASTAL LOCATIONS
FROM THE MOUTH OF THE ATCHAFALAYA RIVER TO THE MISSISSIPPI-ALABAMA
STATE LINE. TIDES UP TO 2.5 ABOVE NORMAL CAN BE EXPECTED WITH A FEW
LOCATIONS SEEING TIDES OF 3 TO 3.5 FEET ABOVE NORMAL LEVELS.

A MARGINAL RISK OF SEVERE THUNDERSTORMS WILL EXIST FOR THE ENTIRE
AREA TONIGHT. THE MAIN CONCERNS WILL BE DAMAGING WINDS AND THE
POSSIBILITY OF AN ISOLATED TORNADO.

A FLASH FLOOD WATCH REMAINS IN EFFECT. HEAVY RAINFALL IS EXPECTED TO
IMPACT SOME AREAS OVERNIGHT WITH A FEW INCHES OF RAINFALL POSSIBLE.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

A FLASH FLOOD WATCH WILL REMAIN IN EFFECT FOR THE ENTIRE AREA
THROUGH SATURDAY AFTERNOON. STORM TOTAL RAINFALL AMOUNTS OF 7 TO 10
INCHES ARE EXPECTED WITH LOCALLY HIGHER AMOUNTS POSSIBLE.

A SMALL CRAFT ADVISORY WILL REMAIN IN EFFECT FOR ALL OF THE
COASTAL WATERS THROUGH FRIDAY FOR HAZARDOUS CONDITIONS FOR SMALL
CRAFT.

A COASTAL FLOOD ADVISORY WILL REMAIN IN EFFECT FOR ALL COASTAL
LOCATIONS FROM THE MOUTH OF THE ATCHAFALAYA RIVER TO THE MISSISSIPPI-
ALABAMA STATE LINE THROUGH FRIDAY. TIDES UP TO 2.5 FEET ABOVE NORMAL
CAN BE EXPECTED WITH A FEW LOCATIONS SEEING TIDES OF 3 TO 3.5 FEET
ABOVE NORMAL LEVELS.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NECESSARY THROUGH SATURDAY...MAINLY FOR
FLOOD REPORTING.