910
FXUS64 KLIX 180844
AFDLIX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
344 AM CDT SAT MAY 18 2013

.SHORT TERM...

NO SIGNIFICANT CHANGES TO THE FORECAST THROUGH MONDAY...AS AN
UPPER LEVEL RIDGE DOMINATES THE REGION. STRONG SUBSIDENCE ALOFT
COMBINED WITH DEEP LAYER SOUTHERLY FLOW OFF THE GULF OF MEXICO
WILL CONTINUE TO BRING A TYPICAL LATE MAY WEATHER REGIME TO THE
REGION. THE SUBSIDENCE AND RESULTANT CAPPING WILL PROHIBIT ANY
PRECIPITATION FOR DEVELOPING THROUGH MONDAY. ADDITIONALLY...THE
SUBSIDENCE COMBINED WITH STRONG SOLAR INSOLATION WILL ALLOW
TEMPERATURES TO CLIMB INTO THE UPPER 80S AND LOWER 90S EACH DAY.
THE AMPLE LOW LEVEL MOISTURE IN PLACE WILL ALSO KEEP OVERNIGHT
LOWS IN THE LOW 70S. DURING THE OVERNIGHT HOURS...THE ELEVATED
INVERSION WILL ALSO PROMOTE THE DEVELOPMENT OF A LOW STRATUS DECK.
THIS LOW CLOUD DECK WILL TEND TO FORM AROUND MIDNIGHT AND LINGER
THROUGH THE EARLY MORNING HOURS. THE CLOUD DECK WILL GRADUALLY MIX
OUT DURING THE MID-MORNING HOURS AS THE INVERSION WEAKENS AND
DRIER MID-LEVEL AIR MIXES DOWN INTO THE LOW LEVELS OF THE
ATMOSPHERE.

.LONG TERM...

HEADING INTO THE MIDDLE OF NEXT WEEK...THERE HAVE BEEN SOME
ADJUSTMENTS TO THE FORECAST...AS ALL OF THE MEDIUM RANGE GUIDANCE
SHOWS A COLD FRONT MOVING THROUGH THE FORECAST AREA. TUESDAY WILL
REMAIN WARM AND HUMID WITH CONTINUED UPPER LEVEL RIDGING
DOMINATING THE REGION. HOWEVER...THE RIDGE AXIS WILL BEGIN TO PULL
EASTWARD TUESDAY NIGHT AS A STRONG LONG WAVE TROUGH DEEPENS OVER
THE PLAINS STATES.

THIS STRONG TROUGH AND ASSOCIATED FRONT WILL SWEEP THROUGH THE
LOWER MISSISSIPPI VALLEY DURING THE DAY ON WEDNESDAY. A SHARP
INCREASE IN OVERALL INSTABILITY IS EXPECTED BY WEDNESDAY AFTERNOON
AS THE CAPPING THAT HAD DOMINATED THE REGION ERODES AND LAPSE
RATES ALOFT IMPROVE DUE TO SOME COOLER AIR ADVECTING IN WITH THE
APPROACHING TROUGH AXIS. INCREASING OMEGA IN THE MID TO UPPER
LEVELS WILL ALSO SUPPORT THE DEVELOPMENT OF CONVECTION WITH DEEPER
AND MORE SUSTAINED UPDRAFTS. ALTHOUGH THE GREATEST FORCING WILL
REMAIN WELL NORTH OF THE REGION...EXPECTED CAPE VALUES IN EXCESS
OF 2000 J/KG OVER NORTHERN ZONES WILL BE MORE THAN ENOUGH TO
SUPPORT SOME STRONGER THUNDERSTORMS. SHEAR VALUES WILL BE FAIRLY
LIMITED AT AROUND 15 KNOTS...SO THE WIND THREAT LOOKS LIMITED AT
THIS TIME.  HOWEVER...SOME HAIL MAY ACCOMPANY THE STRONGEST
CONVECTION AS LAPSE RATES ALOFT STEEPEN THROUGH THE DAY. HAVE WENT
WITH CHANCE POPS FOR AREAS NORTH OF INTERSTATE 12 IN LOUISIANA AND
SOUTHWEST MISSISSIPPI. SLIGHT CHANCE POPS EXIST ELSEWHERE ON
WEDNESDAY. CONVECTION WILL LINGER INTO THE OVERNIGHT HOURS...AS
THE UPPER LEVEL TROUGH AXIS SLOWLY TRANSITS THROUGH THE FORECAST
AREA. BY THURSDAY...THE TROUGH WILL BEGIN TO FINALLY LIFT OUT.
HOWEVER...THE LINGERING FRONTAL BOUNDARY WILL SLOWLY WASH OUT OVER
THE AREA ON THURSDAY. HAVE KEPT IN A SLIGHT CHANCE FOR CONVECTION
TO DEVELOP NEAR THIS BOUNDARY THROUGHOUT THE DAY.

A SECONDARY SURGE OF UPPER LEVEL ENERGY WILL ROUND THE BASE OF THE
UPPER LEVEL TROUGH ON FRIDAY...FORCING A MUCH COOLER AND DRIER
AIRMASS INTO THE REGION. AS THIS REINFORCING COLD FRONT MOVES
THROUGH...SOME ISOLATED CONVECTION COULD SPARK OFF. HAVE DECIDED
TO KEEP A SLIGHT CHANCE OF POPS IN FOR THE AFTERNOON HOURS...EVEN
THOUGH OVERALL INSTABILITY AND FORCING WILL BE LIMITED IN NATURE.
POPS GOING INTO NEXT WEEKEND WILL BE VERY LOW AS THE COOLER AND
DRIER AIRMASS SETTLES OVER THE AREA.

&&

.AVIATION...

MOSTLY MVFR CONDITIONS WILL PREVAIL DUE TO CIGS AND SOME MINOR VSBY
RESTRICTIONS THROUGH ABOUT 14-17Z TODAY WITH A COUPLE AIRPORTS
LIKELY TO HAVE A PERIOD OF IFR CATEGORY CIGS. VFR CONDITIONS WILL
RETURN  BY MIDDAY. LOWER CIGS AND POSSIBLY SOME MINOR VSBY
RESTRICTIONS WILL LEAD TO ANOTHER PERIOD OF MVFR TO IFR CONDITIONS
STARTING AROUND 05Z/MIDNIGHT TONIGHT AND PERSISTING THROUGH MID TO
LATE MORNING ON SUNDAY. 22/TD

&&

.MARINE...

A SURFACE HIGH PRESSURE RIDGE WILL PERSIST AND EXTEND FROM THE
ATLANTIC OCEAN TO THE NORTH GULF COAST REGION THROUGH THE MIDDLE OF
NEXT WEEK. SOUTHEAST TO SOUTH WINDS FROM AROUND 10 KNOTS TO 10 TO 15
KNOTS WILL PERSIST DURING MOST OF THE PERIOD THROUGH
WEDNESDAY...EXCEPT THE WESTERN WATERS MAY BECOME SUSTAINED AROUND
15 KNOTS AT TIMES MONDAY NIGHT AND TUESDAY NIGHT. WAVE HEIGHTS IN
THE COASTAL WATERS SHOULD FALL IN THE TYPICAL RANGES FOR THE
WINDS...MAINLY 2 TO 3 FEET...EXCEPT RISING TO 4 FEET OVER PORTIONS
OF THE WESTERN WATERS MONDAY THROUGH WEDNESDAY MORNING. 22/TD

&&

.DECISION SUPPORT...
DSS CODE...BLUE.
DEPLOYED...NONE.
ACTIVATION...NONE.
ACTIVITIES...SLURRY SUPPORT.
             MONITORING RIVER 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  89  68  88  69 /  10  10  10  10
BTR  90  69  90  71 /  10  10  10  10
ASD  85  70  87  70 /  10  10  10  10
MSY  87  71  87  72 /  10  10  10  10
GPT  83  70  83  71 /  10  10  10  10
PQL  85  67  85  70 /  10  10  10  10

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...NONE.
GM...NONE.
MS...NONE.
GM...NONE.
&&

$$

32