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

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734
FXUS64 KLIX 261020
AFDLIX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
520 AM CDT THU MAR 26 2015

.SHORT TERM...

TWO DIFFERENT STREAMS OF UPPER LEVEL FLOW WITH DIVERGENCE AREAS
AND SHORTWAVE TROUGHS WILL AFFECT THE FORECAST AREA TODAY. THE
MAIN FORECAST PROBLEM WILL BE THE PLACEMENT OF THE TIMING AND
PLACEMENT OF THE MORE WIDESPREAD SHOWERS AND SCATTERED
THUNDERSTORMS ASSOCIATED WITH THESE UPPER LEVEL FEATURES.

ONE SMALL AREA OF SHOWERS AND THUNDERSTORMS BLEW UP EARLIER OVER
THE OFFSHORE WATERS OFF THE SOUTHEAST TEXAS AND SOUTHWEST
LOUISIANA COAST BETWEEN MIDNIGHT AND 1 AM AND THIS HAS QUICKLY
EXPANDED EAST-NORTHEAST AND MOVED INTO THE COASTAL WATERS SOUTH
OF TERREBONNE PARISH. THIS AREA OF CONVECTION DEVELOPED AHEAD OF
A WELL DEFINED SHORTWAVE TROUGH AND THE LEFT EXIT REGION OF AN
UPPER LEVEL JET THAT EXTENDS ACROSS MEXICO INTO THE NORTHWEST
GULF. THIS AREA OF SHOWERS AND THUNDERSTORMS WILL CONTINUE TO
EXPAND EAST AND NORTHEAST THIS MORNING ACROSS PORTIONS OF
SOUTHEAST LOUISIANA AND MORE OF THE COASTAL WATERS. AT THE SAME
TIME...A SHORTWAVE TROUGH OVER THE CENTRAL/SOUTHERN PLAINS REGION
WILL DRIVE EAST SOUTHEAST ACROSS THE LOWER MISSISSIPPI VALLEY
TONIGHT. THE RIGHT ENTRANCE REGION OF THE ASSOCIATED UPPER LEVEL
JET WILL NEARLY COUPLE WITH THE LIFT ASSOCIATED WITH THE SOUTHERN
STREAM JET. THERE MAY BE A ZONE WITH LESS CONVECTION IN BETWEEN
THE EXPANDING AREA TO THE SOUTH AND THE ANTICIPATED DEVELOPMENT TO
THE WEST AND NORTHWEST. HAVE CONTINUED THE PREVIOUS FORECAST
TRENDS WITH CATEGORICAL RANGE POPS OVER THE FAR SOUTH AND LIKELY
ELSEWHERE...AND KEPT THUNDERSTORMS IN THE CHANCE RANGE. A FEW
STRONGER STORMS MAY DEVELOP ACROSS THE WESTERN COASTAL WATERS THIS
MORNING WITH SOME GUSTS POSSIBLY EXCEEDING 30 KNOTS. LOW LEVEL
SHEAR WILL NOT BE IMPRESSIVE...BUT LOW TO MID LEVEL BULK SHEAR
WILL BE A BIT BETTER...AND INSTABILITY WILL BE SLIGHT TO MODERATE
WITH MUCAPES UP NEAR 1000 J/KG AND LIFTED INDICES OF -5 AROUND 4
PM TODAY...HOWEVER THE STRONG COLD FRONT WILL HAVE MOVED THROUGH
MUCH OF THE FORECAST AREA BY THEN. SEVERE THUNDERSTORMS ARE NOT
EXPECTED...HOWEVER A FEW STRONG STORMS WITH GUSTS TO 45 MPH AND
SOME SMALL HAIL WILL BE POSSIBLE.

THE RAIN WILL END THIS EVENING AS THE UPPER LEVEL SUPPORT PULLS
AWAY TO THE NORTHEAST AND EAST. THE STRONG COLD FRONT WILL PUSH
THROUGH COASTAL AREAS EARLY TONIGHT AND MOST OF THE OFFSHORE
COASTAL WATERS BY MIDNIGHT. GUSTY NORTH WINDS AND MUCH COOLER
TEMPERATURES WILL FOLLOW WITH LOWS EXPECTED TO DROP INTO THE 40S
TO NEAR 50.

A FAIRLY DEEP BUT PROGRESSIVE MID/UPPER TROUGH WILL MOVE FROM JUST
EAST OF THE MISSISSIPPI VALLEY EARLY FRIDAY TO NEAR THE EASTERN
SEABOARD FRIDAY NIGHT INTO SATURDAY...AND SURFACE HIGH PRESSURE
WILL TAKE HOLD OVER MOST OF THE EASTERN STATES. HIGHS ON FRIDAY
ARE EXPECTED TO ONLY REACH THE MID 60S WITH AMPLE SUNSHINE...LOW
HUMIDITY AND NORTH BREEZES. FRIDAY NIGHT IS EXPECTED TO BE THE
COOLEST NIGHT WITH LOWS EXPECTED TO DROP INTO THE LOWER TO MID 40S
OVER MOST OF THE REGION EXCEPT NEAR 50 SOUTH OF LAKE
PONTCHARTRAIN. IT WILL REMAIN MOSTLY SUNNY ON SATURDAY WITH THE
HIGHS EXPECTED TO RETURN TO THE LOWER TO MID 70S.

.LONG TERM...

THE ECMWF HAS A CLIPPER TYPE WEAK SYSTEM AND LIGHT TO MODERATE QPF
AMOUNTS MOVING THROUGH THE LOWER MISSISSIPPI VALLEY AND SOUTHEAST
LATE SUNDAY NIGHT THROUGH MONDAY NIGHT. THE GFS HAS A MUCH WEAKER
SYSTEM AND IS DRY. HAVE MAINTAINED THE PREVIOUS FORECAST WITH
SLIGHT CHANCE TO CHANCE MENTION OF SHOWERS AND THUNDERSTORMS
MONDAY AND MONDAY EVENING. THE LOWER CONFIDENCE FORECAST WILL
CONTINUE THROUGH MID WEEK AS THE MODELS HAVE DIFFERING SOLUTIONS
WITH REGARDS TO THE ADDITIONAL DISTURBANCES THAT RIDE THROUGH THE
SOUTHERN STREAM OF THE WESTERLIES. HAVE CONTINUED WITH A SLIGHT
CHANCE OF SHOWERS AND THUNDERSTORMS ON TUESDAY AND A BETTER CHANCE
ON WEDNESDAY AS MORE PRONOUNCED SHORTWAVE TROUGH MAY MOVE THROUGH.
TEMPERATURES ARE EXPECTED TO RETURN TO ABOVE NORMAL SUNDAY THROUGH
THE MIDDLE OF NEXT WEEK. 22/TD

&&

.AVIATION...

MID LEVEL CLOUD DECK IN PLACE WILL LOWER TO MVFR CIGS GOING INTO
THE LATER MORNING HOURS AS SHOWERS MOVE IN. LATEST RADAR IMAGERY
SHOWS SHOWERS APPROACHING THE LOUISIANA COAST AROUND VERMILION BAY
AND MOVING NORTHEAST. MOST TERMINALS SHOULD HAVE SOME IMPACT FROM
RAIN BY AROUND 15Z. MVFR CONDITIONS EXPECTED DURING THIS PERIOD
BUT COULD HAVE TEMPORARY IFR VISIBILITIES WITH MORE INTENSE
CONVECTION. RAIN WILL BE SHIFTING EASTWARD DURING THE EVENING
HOURS AND ALL TERMINALS SHOULD BE RAINFREE BY 06Z. LOW CEILINGS OF
AROUND 1500KFT WILL HANG AROUND THROUGH THE END OF THIS FORECAST
PERIOD.

MEFFER
&&

.MARINE...

SOUTHEAST WINDS ARE RELATIVELY LIGHT ATTM BUT WILL INCREASE
SLIGHTLY AS THEY VEER TO SOUTHWEST AS COLD FRONT APPROACHES.
MODELS IN GOOD AGREEMENT THAT THE BOUNDARY WILL REACH THE MARINE
LOCATIONS AROUND 03Z THIS EVENING. WINDS WILL QUICKLY JUMP UP TO
20+ KNOTS WITH GUSTS IN THE LOW 30S. WILL BE ISSUING A SMALL CRAFT
ADVISORY FOR ALL MARINE ZONES THIS MORNING TO START AT 03Z. SFC
HIGH WILL BE QUICKLY MOVING IN FRIDAY MORNING BEHIND FRONT...SO
LIKELY ENDING THE ADVISORY BY MID MORNING. ELEVATED OFFSHORE FLOW
STILL TO PERSIST THOUGH FRIDAY NIGHT BUT NO ADVISORY NEEDED AS
SPEEDS SHOULD BE LESS THAN 15 KNOTS. WINDS WILL ROTATE BACK AROUND
TO OFFSHORE THROUGH THE WEEKEND AS THE RIDGE SLIDES EAST. WINDS
NOT LIKELY TO CHANGE MUCH THROUGH EARLY NEXT WEEK WITH HIGH
PRESSURE STAYING IN PLACE.

MEFFER
&&

.DECISION SUPPORT...
DSS CODE...GREEN.
DEPLOYED...NONE.
ACTIVATION...NONE.
ACTIVITIES...MONITORING FOG AND CONVECTIVE TRENDS
             FOR LATE TONIGHT AND THURSDAY.


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 TONIGHT RISK SVR
         AND/OR DIRECT TROPICAL THREATS; EVENTS OF NATIONAL
         SIGNIFICANCE

&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  74  42  64  42 /  60  30   0   0
BTR  75  45  67  46 /  60  30   0   0
ASD  74  48  67  43 /  70  40  10   0
MSY  74  51  67  51 /  70  40  10   0
GPT  73  50  67  45 /  70  40  10   0
PQL  75  51  67  41 /  70  50  10   0

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...NONE.
GM...SMALL CRAFT ADVISORY FROM 10 PM THIS EVENING TO 10 AM CDT FRIDAY
     FOR GMZ530-532-534-536-538-550-552-555-557-570-572-575-577.

MS...NONE.
GM...SMALL CRAFT ADVISORY FROM 10 PM THIS EVENING TO 10 AM CDT FRIDAY
     FOR GMZ532-534-536-538-550-552-555-557-570-572-575-577.

&&

$$



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