201
FXUS64 KLIX 211428
AFDLIX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
928 AM CDT TUE MAY 21 2013

.UPDATE...

.SOUNDING DISCUSSION...

NO PROBLEMS WITH THE FLIGHT THIS MORNING. ANOTHER MUGGY MORNING
WITH PLENTY OF INSTABILITY AND MOISTURE NEAR THE SURFACE WITH A PW
OF 1.25 INCHES AND AN LI OF -8.0. A LARGE CAP ABOVE 940 MB...EXPECTED
TO KEEP AFTERNOON AND EVENING CONVECTION TO A MINIMUM. A LIGHT TO MODERATE
SOUTHERLY FLOW IN THE LOWER TO MIDDLE LEVELS WITH A LIGHT TO
MODERATE WEST NORTHWESTERLY FLOW ALOFT.

&&

.PREV DISCUSSION... /ISSUED 534 AM CDT TUE MAY 21 2013/

SHORT TERM...

HIGH PRESSURE IN THE LOWER TO MID LEVELS OF THE ATMOSPHERE WILL
REMAIN IN CONTROL OF THE CENTRAL GULF COAST REGION TODAY. PARTLY
SUNNY SKIES WILL FILTER THROUGH SOME LOWER AND HIGH LEVEL
CLOUDS...SO THE HIGHS TODAY SHOULD ONCE AGAIN PUSH INTO THE 85 TO
90 DEGREE RANGE. MOISTURE DEPTH WILL BE RATHER LIMITED BUT
ADEQUATE FOR A FEW AFTERNOON SHOWERS AND THUNDERSTORMS...MAINLY
OVER SOUTHWEST MISSISSIPPI INTO ADJACENT PORTIONS OF EAST CENTRAL
AND SOUTHEAST LOUISIANA. THE MAIN WEATHER MAKER TODAY AND TONIGHT
WILL BE A STRONG SHORTWAVE TROUGH THAT WILL ADVANCE EAST ACROSS
THE SOUTHERN PLAINS AND REACH THE LOWER MISSISSIPPI VALLEY LATE
TONIGHT AND WEDNESDAY. MID AND UPPER LEVEL DIVERGENCE WILL BECOME
ENHANCED ON THE SOUTHEAST PERIPHERY OF THE SHORTWAVE TROUGH DUE TO
THE RIGHT ENTRANCE REGION OF THE MAIN UPPER JETSTREAM CORE ON THE
EAST SIDE OF THE SYSTEM...AND IN A SHARPLY SPLITTING UPPER WIND
FLOW REGIME BETWEEN THE SHORTWAVE TROUGH AND A SHORTWAVE RIDGE
OVER THE NORTH GULF OF MEXICO. THERE IS A MODERATE RISK OF SEVERE
THUNDERSTORMS TODAY AND TONIGHT ACROSS THE ARKLATEX REGION WITH A
SLIGHT RISK EXTENDING AS FAR SOUTHEAST AS NORTHEAST AND WEST
CENTRAL LOUISIANA AND WEST CENTRAL MISSISSIPPI...OR JUST NORTHWEST
OF THE FORECAST AREA.

ON WEDNESDAY...THE SOUTHERN PORTION OF THE SHORTWAVE TROUGH WILL
MOVE THROUGH THE FORECAST AREA ALONG WITH AN AREA OF ENHANCED
UPPER DIVERGENCE AND DEEPER MOISTURE. A WEAKENING FRONTAL BOUNDARY
MAY BRUSH THE NORTHWEST PORTION OF THE FORECAST AREA BY LATE
WEDNESDAY...BUT THE MAIN LOW LEVEL FOCUS WILL COME FROM ANY
THUNDERSTORM OUTFLOW BOUNDARIES. HAVE MAINTAINED THE HIGHEST
CHANCES OF THUNDERSTORMS ACROSS THE NORTH AND NORTHWEST WITH A
TAPERING OFF TO LOWER CHANCE RANGE NEAR THE COAST AND EVEN LESS
OFFSHORE IN THE GULF. MOST OF THE LAND AREAS OF THE FORECAST AREA
REMAIN IN A /SEE TEXT/ OR 5 PERCENT PROBABILITY FOR SEVERE
THUNDERSTORMS ON WEDNESDAY...AND THE MAIN THREATS STILL APPEAR TO
BE A FEW STORMS WITH STRONG GUSTY WINDS AND HAIL.

THE MAIN FORCING FROM THE SHORTWAVE AND UPPER JETSTREAM WILL
QUICKLY EXIT THE AREA WEDNESDAY EVENING...SO WILL HAVE DIMINISHING
RAIN CHANCES WEDNESDAY NIGHT. NORTHWEST FLOW ALOFT WILL SET UP ON
THURSDAY...AND ANOTHER WEAK SHORTWAVE TROUGH/VORT LOBE WILL LIKELY
MOVE THROUGH THE FORECAST AREA. MOISTURE WILL BECOME LIMITED
AGAIN...HOWEVER...STRONG DAYTIME HEATING WILL LIKELY RESULT IN
ADEQUATE INSTABILITY AND LIFT FOR ISOLATED TO LOW END SCATTERED
DIURNAL SHOWERS AND THUNDERSTORMS. THE RISK OF SEVERE STORMS
SHOULD REMAIN LOW...BUT AN ISOLATED STRONG STORM CANNOT BE RULED
OUT.

LONG TERM...

THE MODELS HAVE TRENDED EVEN DRIER FOR THE ENTIRE HOLIDAY WEEKEND
FROM FRIDAY THROUGH MEMORIAL DAY/MONDAY AS HIGH PRESSURE AT ALL
LEVELS TAKE CONTROL. THE MOST SIGNIFICANT CHANGE TODAY IS A TREND
FOR A BACKDOOR COLD FRONT TO COME IN STRONGER RESULTING IN SOME
SUBSTANTIALLY COOLER NIGHTTIME LOWS AND LOWER HUMIDITY LEVELS.
THE GFS IS THE MOST AGGRESSIVE WITH THIS BRINGING MID TO UPPER 50S
DEWPOINTS INTO NORTHERN PORTIONS OF THE AREA FRIDAY AND LOWER TO
MID 50S DEWPOINTS OVER MOST AREAS ON SATURDAY...BEFORE MODIFYING
SLOWLY SUNDAY AND MONDAY. THE ECMWF ONLY LOWERS THE DEWPOINTS INTO
THE 60S DURING THE PERIOD. HAVE GONE WITH NO MENTION OF RAIN
DURING THE PERIOD...AND HAVE LOWERED THE NIGHTTIME LOWS...BUT NOT
QUITE AS LOW AS THE GFS MEX GUIDANCE. 22/TD

AVIATION...

LITTLE CHANGE IN THE PATTERN OVER THE LAST SEVERAL DAYS...AND NOT
MUCH CHANGE ANTICIPATED UNTIL WEDNESDAY AFTERNOON.

OVERNIGHT FORECAST MONITORING HAS BEEN PLAGUED BY LACK OF TIMELY
SURFACE OBSERVATIONS DUE TO A NATIONAL DATA OUTAGE. DATA IS NOW
FLOWING...WITH THE DATA QUEUE SHRINKING. WILL BE AMENDING FORECASTS
REMOVING THE AMD NOT SKED REMARK WITH DATA FLOWING.

MOST AREAS THAT ARE SEEING CLOUD DECKS ARE SEEING THEM IN THE
FL010-FL020 RANGE. THE EXCEPTION AT THIS POINT IS KMCB WHERE IFR
CONDITIONS ARE OCCURRING. COULD SEE BRIEF IFR ELSEWHERE. WITH WINDS
REMAINING AROUND 5 KNOTS...FOG SHOULD NOT BE AN ISSUE THIS MORNING.
CONDITIONS SHOULD IMPROVE AROUND 15Z WITH CEILINGS ALL ABOVE FL020.
ANY CONVECTIVE DEVELOPMENT TODAY WILL BE ISOLATED AND NOT MENTIONED
IN 12Z FORECAST PACKAGE. A REPEAT OF CURRENT SCENARIO WILL BE
REPORTED OVERNIGHT TUESDAY NIGHT/WEDNESDAY MORNING. 35

MARINE...

RIDGE OF HIGH PRESSURE CENTERED IN THE WESTERN ATLANTIC EXTENDS INTO
THE NORTHEAST GULF OF MEXICO. IT WILL SLOWLY RETREAT EAST THROUGH
WEDNESDAY. THIS WILL KEEP WINDS SOUTHEASTERLY AT 10 TO 15
KNOTS...POSSIBLY A TOUCH ABOVE 15 KNOTS BRIEFLY IN SPOTS. SEAS THRU
THAT PERIOD TO BE MAINLY IN THE 2 FOOT RANGE...WITH THE EXCEPTION OF
THE WESTERN WATERS WITH 3 TO 4 FOOT WAVES POSSIBLE TODAY WITH
PERSISTENT WINDS NEAR 15 KNOTS.

UPPER LEVEL TROUGH WILL DIG ACROSS THE EASTERN HALF BEGINNING MID
WEEK. THIS WILL BREAK DOWN RIDGE OVER THE GULF COAST AND CAUSE THE
WIND FIELD TO BREAKDOWN. A WEAK FRONTAL BOUNDARY WILL PASS THROUGH
FRIDAY MORNING WITH A WIND SHIFT TO THE NORTH THROUGH MUCH OF THE
WEEKEND. 18/35

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  68  86  66  89 /  20  50  20  30
BTR  73  88  69  90 /  20  50  20  30
ASD  72  86  69  89 /  10  30  20  30
MSY  74  87  72  87 /  10  30  20  30
GPT  73  84  71  86 /  10  30  20  30
PQL  67  85  67  87 /   0  30  20  30

&&

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

$$