202
FXUS64 KLIX 110826
AFDLIX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
326 AM CDT SAT MAY 11 2013

.SHORT TERM...SEVERAL MORE ROUNDS OF SHOWERS AND THUNDERSTORMS
REMAIN BEFORE A SLOW MOVING COLD FRONT PUSHES OFFSHORE TONIGHT. AN
UPPER LEVEL TROUGH AXIS HAS A HOLD ON THE REGION. SEVERAL FAST MOVING
PERTURBATIONS MOVE ALONG THE AXIS PROVIDING THE INSTABILITY TO
KICK HEAVY RAIN. IR SATELLITE SHOWS 2 SUCH IMPULSES POISED TO MOVE
THROUGH. THE FIRST IS ASSOCIATED WITH THE RAIN INDICATED ON RADAR
IN SW LA AND THE OTHER FURTHER WEST IN S TX. EXPECT THE FIRST
IMPULSE TO BRING HEAVY RAIN THIS MORNING AND THE 2ND TO BRING
ANOTHER ROUND OF HEAVY RAIN LATER THIS MORNING ON INTO THE
AFTERNOON HOURS.

PREVIOUS SOUNDING MEASURED A PW OF 1.58 WITH VERY LITTLE TEMP DEW
POINT SPREADS THROUGH 35K FEET.  GFS AND ECMWF HAVING SOME
DIFFICULTY HANDLING THE SITUATION...SEEMS MESO MODELS INITIALIZING
BETTER PER WSR88D. GFS HAS THE BULK OF THE RAIN FURTHER SOUTH THAN OTHER
MODEL SOLUTIONS. THE RUC SEEMS TO HAVE THE BEST HANDLE ON THIS
EVENT WITH A 850 THETA E RIDGE MOVING FROM NORTH FROM THE COAST.
EXPECT THE CONVECTION AND HEAVY RAIN TO FOLLOW THE THETA E AXIS.
MESO MODELS ALSO SHOW INCREASING UPPER LEVEL DIVERGENT FLOW WITH
SOME DEGREE OF SFC CONVERGENCE. THE THETA E AXIS... IMPULSE
INDUCED LIFT...UPPER LEVEL DIVERGENCE AND LOW LEVEL CONVERGENCE
ALL ADD UP TO THE POTENTIAL OF HEAVY RAIN. FFG VALUES AVERAGE OUT
TO BE AROUND 1.6 TO 2.1 INCHES AN HOUR FOR MOST LOCATIONS. HOWEVER...
SEVERAL LOCATIONS ARE AT PARTICULAR RISK WITH .5 INCHES FOR AN
HOUR AND EVEN .6 INCHES IN A 6 HOUR PERIOD. RAIN ALONG THE COASTAL
LA PARISHES SUCH AS TERREBONNE AND LAFOURCHE WILL CAUSE FLASH
FLOOD ISSUES EXPANDING TO OTHER AREAS TODAY. ROUND ONE WILL BEGIN
AROUND 10Z WITH ROUND TWO NEAR 17Z.

THE COLD FRONT WILL PUSH THROUGH TONIGHT AND WILL BRING COOLER AND
DRIER AIR INTO THE ENTIRE AREA.

.LONG TERM...
WE HAVE A CHANCE TO DRY OUT SUNDAY THROUGH MID WEEK. AN UPPER
TROUGH DIGS INTO THE AREA WED NIGHT AND INTO THURSDAY BRINGING
RAIN CHANCES BACK INTO THE FORECAST. SO FAR... THIS SYSTEM DOES
NOT APPEAR TO BE AS MOIST AND PROLONGED AS THE PREVIOUS. LOOKS LIKE
DIURNAL CONVECTION IS POSSIBLE LATE IN THE WEEK.

&&
.MARINE...THE PRESSURE GRADIENT HAS WEAKENED SOME AS THE COLD FRONT
DRIFTS EVER CLOSER TO THE REGION. WEAK TO MODERATE ONSHORE FLOW WILL
GENERALLY CONTINUE THROUGH THE DAY BUT THE FRONT WILL FINALLY PUSH
INTO THE GULF OVERNIGHT AND WINDS WILL BECOME NRLY BEHIND IT.
MODERATE OFFSHORE WINDS ARE EXPECTED TOMORROW BUT AS HIGH PRESSURE
PUSHES INTO THE LOWER MS VALLEY THE PRESSURE GRADIENT WILL TIGHTEN
ACROSS THE NCNTRL AND NERN GULF AND THIS COULD LEAD TO STRONG
OFFSHORE WINDS OVERNIGHT SUN BEFORE FINALLY RELAXING MON AS HIGH
PRESSURE FINALLY SITS IN RIGHT OVER THE AREA. LGT WINDS ARE THEN
EXPECTED THROUGH THE MIDDLE OF THE WEEK AS HIGH PRESSURE DOMINATES
THE REGION. /CAB/

&&

.AVIATION...ALL SORTS OF AVIATION ISSUES THIS MORNING. MOST
TERMINALS ARE DEALING WITH CIG OR VSBY REDUCTIONS OR BOTH.
TERMINALS ARE RANGING FROM MVFR TO IFR WITH VSBYS GENERALLY B/T 2
AND 5SM AND CIGS FROM AS LOW AS 600 TO 5K FT. UNTIL CONVECTION MOVES
BACK IN NOT EXPECTING CONDITIONS TO CHANGE MUCH BESIDES BOUNCE
BETWEEN IFR AND MVFR...EVEN TEMPORARILY DROPPING TO LIFR AT TIMES.
CONVECTION SHOULD BEGIN TO IMPACT BTR B/T 915 & 945Z WITH EACH
TERMINAL TO THE EAST SEEING CONVECTION IN UNDER AND HOUR OR 2
AFTERWARD. CURRENT TIMING HAS MSY SEEING CONVECTION NEAR
1030-1045Z. OF COURSE CIGS AND VSBYS WILL BE REDUCED SIGNIFICANTLY
WITH THE CONVECTION AND FREQUENT LIGHTNING WILL BE AN ISSUE AGAIN.
WIND GUSTS WILL BE A PROBLEM BUT DO NOT APPEAR TO BE AS MUCH OF AN
ISSUE AS THEY WERE YESTERDAY. CONVECTION SHOULD FINALLY CLR OUT
AFTER 20Z. /CAB/

&&

.DECISION SUPPORT...

DSS CODE...YELLOW.
DEPLOYED...NONE.
ACTIVATION...NONE.
ACTIVITIES...SLURRY SUPPORT
             MONITORING RIVERS
             MONITORING CONVECTION FOR SEVERE AND FLASH FLOODING

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  77  55  78  49 /  80  20  10  10
BTR  79  57  79  51 /  80  20  10  10
ASD  78  58  78  51 /  80  30  10  10
MSY  77  63  78  57 /  80  30  10  10
GPT  77  59  78  52 /  80  40  10  10
PQL  79  58  78  50 /  80  40  10  10

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...FLASH FLOOD WATCH UNTIL 1 AM SUNDAY FOR THE FOLLOWING ZONES:
     ASCENSION...ASSUMPTION...EAST BATON ROUGE...EAST
     FELICIANA...IBERVILLE...LIVINGSTON...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...FLASH FLOOD WATCH UNTIL 1 AM SUNDAY FOR THE FOLLOWING ZONES:
     AMITE...HANCOCK...HARRISON...JACKSON...PEARL
     RIVER...PIKE...WALTHALL...AND WILKINSON.

GM...NONE.
&&

$$