023
FXUS64 KLIX 201410
AFDLIX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
910 AM CDT MON MAY 20 2013

.UPDATE...

.SOUNDING DISCUSSION...

NO PROBLEMS WITH THE FLIGHT THIS MORNING. A VERY SUMMER-LIKE
MORNING WITH PLENTY OF INSTABILITY AND MOISTURE NEAR THE SURFACE
WITH A PW OF 1.37 INCHES AND AN LI OF -8.2. A SIGNIFICANT CAP ABOVE
850 MB...EXPECTED TO KEEP AFTERNOON AND EVENING CONVECTION TO A
MINIMUM. A MODERATE SOUTHERLY FLOW IN THE LOWER TO MIDDLE LEVELS
WITH A LIGHT TO MODERATE WEST NORTHWESTERLY FLOW ALOFT.

&&

.PREV DISCUSSION... /ISSUED 510 AM CDT MON MAY 20 2013/

SHORT TERM...

LOW TO MID LEVEL HIGH PRESSURE TO THE EAST OF THE FORECAST AREA
WILL BE GRADUALLY WEAKENING...BUT WILL CONTINUE TO INFLUENCE THE
WEATHER PATTERN ACROSS THE FORECAST AREA THROUGH TUESDAY AS A
SHORTWAVE TROUGH MOVES OUT OF THE SOUTHERN ROCKIES INTO THE
SOUTHERN PLAINS. ISOLATED /10 TO 15 PERCENT COVERAGE/ AFTERNOON
SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE ACROSS PORTIONS OF EAST
CENTRAL AND SOUTHEAST LOUISIANA TODAY DUE TO A COMBINATION OF
SLIGHTLY HIGHER TEMPERATURES THAN YESTERDAY AND THE EXPECTED
WEAKENING OF THE STRONG CAPPING INVERSION BETWEEN 800 AND 700 MB.
THIS CAP WAS MAINTAINED YESTERDAY DUE TO MID LEVEL SUBSIDENCE IN
THE WAKE OF A POTENT SHORTWAVE TROUGH THAT MOVED THROUGH...BUT
THAT SHOULD NOT BE A SOURCE OF MID LEVEL WARMING TODAY AS
PERSISTENT SOUTHERLY WINDS ARE EXPECTED FROM THE SURFACE UP TO
ABOUT 600 MB. IN ADDITION...THE UPPER LEVEL WINDS WILL START TO
BECOME DIFFLUENT TODAY AND ESPECIALLY ON TUESDAY BETWEEN
ANTICYCLONIC FLOW OVER THE GULF OF MEXICO AND CYCLONIC FLOW NEAR
THE APPROACHING SHORTWAVE TROUGH OVER THE PLAINS. ISOLATED
AFTERNOON SHOWERS AND THUNDERSTORMS ARE AGAIN EXPECTED ON TUESDAY
INLAND FROM THE COAST.

HAVE GONE SLIGHTLY ABOVE THE MAV MOS POP GUIDANCE AND BLENDED IN
SOME OF THE ECMWF QPF WHICH HAS CONSISTENTLY BEEN SHOWING SOME
LIGHT PRECIPITATION. THE MOS GUIDANCE HAS ALSO CONTINUED TO
STRUGGLE WITH KEEPING DEWPOINTS AND THE LOW TEMPERATURES HIGH
ENOUGH...SO HAVE MADE UPWARD ADJUSTMENTS FOR TONIGHT AND TUESDAY
NIGHT.

ON TUESDAY NIGHT AND WEDNESDAY...THE SHORTWAVE TROUGH IS EXPECTED
TO GRADUALLY WEAKEN AS IT MOVES EAST ACROSS THE LOWER MISSISSIPPI
VALLEY...AND THERE IS NO FRONTAL BOUNDARY TO FOCUS CONVECTION.
HOWEVER...PRECIPITABLE WATER IS EXPECTED TO INCREASE TO 1.6 TO
1.9 INCHES ACROSS THE FORECAST AREA AS UPPER LEVEL DIVERGENCE
INCREASES DUE TO THE RIGHT ENTRANCE REGION OF THE UPPER JET CORE
ON EAST SIDE OF THE SHORTWAVE TROUGH. HAVE TRENDED THE POP BACK UP
ACROSS MUCH OF THE FORECAST AREA AND THE RAIN CHANCE MAY HAVE TO
BE RAISED A BIT MORE LATER IF THE GFS AND NAM TREND TOWARDS THE
WETTER ECMWF. CONVECTION MAY FOCUS ON THUNDERSTORM OUTFLOW
BOUNDARIES WHICH MAY RESULT IN SOME MORE ORGANIZED STORMS CAPABLE
OF PRODUCING BOTH STRONG GUSTY WINDS AND HAIL. THE STORM
PREDICTION CENTER HAS THE FORECAST AREA IN A /SEE TEXT/ OR 5
PERCENT PROBABILITY OF SEVERE THUNDERSTORMS ON WEDNESDAY...AND
THIS LOOKS REASONABLE GIVEN THE WEATHER PATTERN. WILL MENTION A
FEW STRONG TO SEVERE STORMS IN THE HAZARDOUS WEATHER OUTLOOK.

LONG TERM...

THE SLOWER MOVING NORTHERN PORTION OF THE UPPER TROUGH WITH A MID
LEVEL LOW ACROSS THE NORTHERN PLAINS ON TUESDAY IS EXPECTED TO
EVENTUALLY MOVE SOUTHEAST ACROSS THE LOWER OHIO VALLEY ON THURSDAY
AND THE MID ATLANTIC AND SOUTHERN APPALACHIANS REGION THURSDAY
NIGHT AND FRIDAY. THERE MAY BE SOME MINOR EFFECTS OF THE NORTHWEST
FLOW ASSOCIATED WITH THIS SYSTEM THAT WILL EXTEND DOWN TO THE
CENTRAL GULF COAST...HOWEVER...LOW TO MID LEVEL HIGH PRESSURE
WILL BE GRADUALLY BE BUILDING BACK INTO THE FORECAST AREA THURSDAY
INTO FRIDAY. THERE SHOULD BE ENOUGH RESIDUAL MOISTURE AND
INSTABILITY FOR ISOLATED DIURNAL SHOWERS AND THUNDERSTORMS INTO
FRIDAY...THEN IT LOOKS LIKE THERE WILL BE VERY LITTLE OR NO RAIN
OVER THE HOLIDAY WEEKEND AS HIGH PRESSURE BUILDS WITH THE
EXCEPTION BEING ON MEMORIAL DAY WHEN THE RIDGE MAY WEAKEN
SLIGHTLY...BUT THE RAIN CHANCE WILL LIKELY BE 20 PERCENT OR LESS.
22/TD

AVIATION...

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

AS HAS BEEN THE CASE THE LAST SEVERAL NIGHTS...MOISTURE TRAPPED
BELOW THE NOCTURNAL INVERSION HAS ALLOWED LOW STRATUS TO DEVELOP
ACROSS THE AREA. CURRENTLY CEILINGS ARE A LITTLE MORE PREVALENT AT
TERMINALS ALONG AND NORTH OF INTERSTATE 12...AT KASD...KHDC...KBTR
AND KMCB...WITH SCATTERED STRATUS ELSEWHERE. EXPECT CONDITIONS TO
BECOME WIDESPREAD BY 10Z WITH CEILINGS GENERALLY IN THE FL005-FL015
RANGE. ANY IFR CEILINGS SHOULD IMPROVE TO MVFR BY ABOUT 14Z...AND TO
FL025-FL030 BY MIDDAY. NOT EXPECTING ANY SIGNIFICANT CONVECTION. A
REPEAT OF THIS MORNINGS CONDITIONS AND TIMING IS ANTICIPATED IN THE
FOLLOWING OVERNIGHT PERIOD. 35

MARINE...

HIGH PRESSURE CENTERED IN THE WESTERN ATLANTIC EXTENDS INTO THE GULF
OF MEXICO. IT WILL REMAIN IN PLACE OVER THE COASTAL WATERS IN THAT
FASHION THROUGH TUESDAY NIGHT WHICH WILL KEEP WINDS SOUTHEASTERLY AT
10 TO 15 KNOTS...POSSIBLY A TOUCH ABOVE 15 KNOTS BRIEFLY IN THE FAR
WESTERN WATERS. SEAS THRU THAT PERIOD TO BE MAINLY IN THE 2 TO 3
FOOT RANGE...WITH THE EXCEPTION OF THE WESTERN WATERS...WHERE SOME 4
FOOTERS ARE POSSIBLE TONIGHT AND TUESDAY 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
AT THE END OF THIS WEEK. ONLY EXPECTING A WIND SHIFT AT THIS
POINT...WITH OFFSHORE FLOW TO BEGIN FRIDAY...AND LAST THROUGH MUCH
OF THE WEEKEND. 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  88  71  88  68 /  10  10  10  20
BTR  89  73  89  72 /  10  10  10  20
ASD  87  73  87  70 /  10   0  10  10
MSY  88  74  87  73 /  10  10  10  10
GPT  84  73  83  72 /  10   0  10  10
PQL  86  68  86  68 /   0   0   0  10

&&

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

$$