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

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FXUS64 KLIX 252158
AFDLIX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
358 PM CST THU DEC 25 2014

.SHORT TERM...
AFTER A NICE CHRISTMAS DAY WE CAN EXPECT A PLEASANT EVENING AND
OVERNIGHT. HIGH PRESSURE CENTERED OVER THE AREA WILL QUICKLY SHIFT
TO THE EAST AHEAD OF A DEVELOPING STORM SYSTEM OVER THE CENTRAL
PLAINS. THIS SYSTEM WILL CONTINUE TO DIVE SOUTHWARD OVER THE NEXT
FEW DAYS. STILL EXPECTING A FAIRLY QUIET DAY FOR TOMORROW AND
RETURN FLOW SHOULD SET UP LATE FRIDAY AFTERNOON AND EVENING. THIS
WILL INCREASE THE MOISTURE ACROSS THE REGION. WITH THAT RAIN
CHANCES WILL INCREASE LATER ON FRIDAY WITH ONLY A FEW SHOWERS
POSSIBLE LATE ON FRIDAY BEFORE THE AFOREMENTIONED SYSTEM IMPACTS
THE AREA ON SATURDAY.

.LONG TERM...
THE BIG WEATHER MAKER FOR THIS WEEKEND WILL BE A SYSTEM MOVING
INTO THE AREA ON SATURDAY. OUT AHEAD OF THIS SYSTEM WE WILL HAVE
INCREASING MOISTURE AS A PERSISTENT SOUTHEASTERLY FLOW OFF THE
GULF PRIMES THE AREA FOR SOME HEAVY RAINFALL. AS THE HIGH OFF TO
THE EAST AND THE DEEPENING LOW AND FRONT APPROACHING THE
AREA...THIS WILL SET UP A PERSISTENT SOUTHWEST FLOW ACROSS THE
AREA SATURDAY AND SUNDAY WITH CONTINUOUS BROAD SCALE LIFT OVER THE
AREA SHOULD SET UP A PRETTY LONG DURATION RAIN EVENT FOR THE DEEP
SOUTH. DIVING INTO SOME OF THE NUMBERS OF THE SITUATION...THERE
WILL BE ENOUGH INSTABILITY ON SATURDAY FOR THE STORM PREDICTION
CENTER TO HIGHLIGHT A MARGINAL RISK FOR SEVERE WEATHER ON
SATURDAY. IT LOOKS LIKE STRONG WINDS WOULD BE THE MAIN
THREAT...THERE IS A SMALL WINDOW OF INCREASED HELICITY OVER THE
AREA MIDDAY SATURDAY BUT AS THAT SOUTHWEST FLOW KICKS IN THE
HELICITY QUICKLY DIMINISHES. WILL HAVE TO WATCH FOR A FEW STRONG TO
SEVERE STORMS ON SATURDAY...BUT THE MAIN THREAT THIS WEEKEND WILL
BE HEAVY RAINFALL WITH SOME POSSIBLE FLOODING ISSUES.

DEEP LAYER MOISTURE...WITH PRECIPITABLE WATER VALUES IN THE 1.7 TO
NEAR 2.0 INCH RANGE ARE VERY IMPRESSIVE FOR THIS TIME OF YEAR. IN
FACT THIS IS IN BETWEEN THE 99TH PERCENTILE AND THE OBSERVED MAX
FOR THIS TIME OF YEAR...THIS IS RED FLAG IN TERMS OF FLOOD
POTENTIAL. THESE TYPES OF VALUES ARE NEAR 200 PERCENT OF NORMAL
FOR THIS TIME OF YEAR. ALSO LOOKING AT SOME OF THE HISTORICAL
ANALOGS FOR THIS TYPE OF EVENT...IT IS POINTING AT HEAVY RAINFALL
POTENTIAL ACROSS PORTIONS OF THE DEEP SOUTH. BOTH OF THESE POINTS
COUPLED WITH THE DEPTH OF THE WARM CLOUD LAYERS...UNIDIRECTIONAL
HODOGRAPHS...BROAD SCALE LIFT...AND THE POSSIBILITY OF TRAINING
SHOWERS AND THUNDERSTORMS HAVE CAUSED US TO ISSUE A FLOOD WATCH
FOR THE ENTIRE FORECAST AREA STARTING LATE FRIDAY NIGHT AND
LASTING THROUGH SUNDAY EVENING. THE WEATHER PREDICTION CENTER
FORMALLY THE HYDROLOGICAL PREDICTION CENTER HAS HIGHLIGHTED
PORTIONS OF OUR AREA FOR A SLIGHT RISK OF FLOODING ON SATURDAY IN
THEIR EXCESSIVE RAINFALL OUTLOOK. THIS IS SIMILAR TO THE STORM
PREDICTION CENTER SEVERE WEATHER OUTLOOK. SO MULTIPLE SOURCES AND
INDICATORS POINT TO SOME POTENTIAL FOR A PRETTY SIGNIFICANT
RAINFALL EVENT FOR THE DEEP SOUTH. WITH ALL OF THAT BEING
SAID...WE EXPECT RAINFALL TOTALS OF 2 TO 4 INCHES WITH SOME
LOCALLY HIGHER AMOUNTS OF 6 INCHES PLUS OVER THE AREA THROUGH
SUNDAY NIGHT. EXPECT THE HIGHER AMOUNT TO OCCUR WHERE
THUNDERSTORMS TRAIN AND LOCAL CONVERGENCE ZONES WHERE HEAVY RAIN
WILL PERSIST. PLEASE STAY TUNED TO OUR FORECASTS AND VARIOUS PAGES
FOR UPDATES AS THE EVENT DRAWS NEAR.

THE FRONT WILL TAKE ITS TIME MOVING OUT OF THE AREA. GUIDANCE IS TRENDING
DRIER FOR MONDAY AND TUESDAY. WILL HOLD SLIGHT POPS FOR MONDAY BUT
WILL REMOVE RAIN CHANCES ON TUESDAY. ANOTHER SOUTHWESTERN TROF
WILL APPROACH TOWARD THE END OF NEXT WEEK...BUT SOME DIVERGENCE IN
SOLUTIONS...AND WILL CONTINUE PREVIOUS FORECAST WITH A BLEND FOR
THE EXTENDED FORECAST. 13/MH

&&

.AVIATION...
VFR CONDITIONS SHOULD HOLD AT MOST LOCATIONS THOUGH SOME NEAR
COASTAL TERMINALS MAY GET A BRIEF MVFR CIG AS MARINE LAYER BEGINS
ADVECTING NORTHWARD FRI MORNING. 24/RR

&&

.MARINE...
HIGH PRESSURE WILL MOVE EAST STEADILY WITH RETURN FLOW BECOMING
ESTABLISHED FRIDAY. SOME BAROCLINIC RETURN SHOULD PROVIDE A BRIEF
PERIOD OF GUSTINESS AS WARM FRONTOGENESIS TAKES PLACE OVER THE NORTH
GULF. THERE MAY BE A NEED FOR `EXERCISE CAUTION` HEADLINES FOR
FRIDAY AS CONVERGENT FLOW REACHES MODERATE LEVELS BEFORE RELAXING
SATURDAY AFTERNOON. COLD FRONT THEN MOVES THROUGH THE NORTH GULF
WATERS SUNDAY AFTERNOON BUT WITH LIMITED COLD AIR ADVECTION. 24/RR

&&

.DECISION SUPPORT...
DSS CODE...BLUE.
DEPLOYED...NONE.
ACTIVATION...NONE.
ACTIVITIES...SLURRY SUPPORT
             ASSESSING FLOOD WATCH POTENTIAL FOR THE WEEKEND

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  40  63  56  70 /  10  30  50  90
BTR  43  66  59  73 /  10  40  60  90
ASD  43  65  59  71 /  10  40  60  90
MSY  48  67  61  72 /  10  40  70  90
GPT  46  64  59  70 /  10  30  70  90
PQL  42  65  57  70 /  10  30  70  90

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...FLOOD WATCH FROM MIDNIGHT SATURDAY TO 6 PM SUNDAY FOR THE
     FOLLOWING ZONES: ASCENSION...ASSUMPTION...EAST BATON
     ROUGE...EAST FELICIANA...IBERVILLE...LIVINGSTON...LOWER
     JEFFERSON...LOWER LAFOURCHE...LOWER PLAQUEMINES...LOWER ST.
     BERNARD...LOWER TERREBONNE...NORTHERN
     TANGIPAHOA...ORLEANS...POINTE COUPEE...SOUTHERN
     TANGIPAHOA...ST. CHARLES...ST. HELENA...ST. JAMES...ST.
     JOHN THE BAPTIST...ST. TAMMANY...UPPER JEFFERSON...UPPER
     LAFOURCHE...UPPER PLAQUEMINES...UPPER ST. BERNARD...UPPER
     TERREBONNE...WASHINGTON...WEST BATON ROUGE...AND WEST
     FELICIANA.

GM...NONE.
MS...FLOOD WATCH FROM MIDNIGHT SATURDAY TO 6 PM SUNDAY FOR THE
     FOLLOWING ZONES:
     AMITE...HANCOCK...HARRISON...JACKSON...PEARL
     RIVER...PIKE...WALTHALL...AND WILKINSON.

GM...NONE.
&&

$$






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