Severe Thunderstorm Warning 100, NWS New Orleans, LA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
307 PM CDT MON MAY 11 2009

.SYNOPSIS...
WEAK SURFACE BOUNDARY NOTED TO THE NORTH OF INTERSTATES 10 AND 12.
HAVE OBSERVED ISOLATED CONVECTION OVER COASTAL MISSISSIPPI WITH
THIS BOUNDARY. MORE SIGNIFICANT...AT LEAST FOR NOW...AREA OF
CONVECTION IS OVER WESTERN AND NORTHERN LOUISIANA FROM NEAR MONROE
TO NORTH OF LAKE CHARLES...AND MOVING EASTWARD. TEMPERATURES
GENERALLY IN MIDDLE AND UPPER 80S WITH DEW POINTS IN THE 60S.

MINOR INTEREST...BUT NOT OF MAJOR METEOROLOGICAL SIGNIFICANCE...IS THE
FACT THAT SURFACE WINDS HAVE ACTUALLY BEEN LIGHT ENOUGH TODAY TO ALLOW
THE DEVELOPMENT OF A LAKE BREEZE OFF OF LAKE PONTCHARTRAIN...AS
REFLECTED BY WIND DIRECTIONS AT MSY...NEW AND ASD ALL BEING DOWNWIND
FROM THE LAKE.
&&

.SHORT TERM...
MAIN FORECAST PROBLEM WILL BE CHANCES FOR CONVECTION. AT CURRENT
PACE...CONVECTION TO OUR WEST SHOULD MOVE INTO OUR AREA CLOSE TO
SUNSET...REACHING BATON ROUGE AROUND 01Z. QUESTION IS WHAT THE
EFFECT OF THE LOSS OF SURFACE HEATING WILL HAVE ON THE CONVECTION.
STRONGEST CONVECTION APPEARS TO BE WITH THE SOUTHERN END OF THE
LINE...WHICH SHOULD SINK SOUTHWARD INTO THE GULF. SPC ISSUING
SEVERE BOX FOR EXTREME WESTERN PORTION CWA UNTIL 01Z. FOR
NOW...WILL KEEP POPS IN CHANCE RANGE...BUT RESERVE THE RIGHT TO
BUMP THEM HIGHER BEFORE PRESS TIME.

BOUNDARY WILL REMAIN IN THE AREA TOMORROW BEFORE LIFTING NORTHWARD.
EXPECT A REPLAY TOMORROW OF TODAYS CONVECTIVE DEVELOPMENT...WITH
POPS MAINLY IN CHANCE RANGE. AFTER THAT...POPS DROP OUT OF SHORT
TERM FORECAST. TEMPERATURES WILL REMAIN ABOVE NORMAL THROUGH SHORT
TERM PORTION OF FORECAST. 35
&&

.LONG TERM...
WEAK UPPER RIDGE WILL CENTER ALONG THE EAST COAST...ALLOWING
MOISTURE TO RETURN FOR THE END OF THE WEEK. THIS WILL PERMIT THE
DEVELOPMENT OF ISOLATED TO SCATTERED CONVECTION DURING THE HEAT OF
THE DAY FRIDAY AND SATURDAY. MEDIUM RANGE MODELS BRING A FRONT
INTO THE AREA FOR SUNDAY...AND MOVE IT THROUGH THE AREA. POPS WILL
BE A LITTLE HIGHER SUNDAY THAN FRIDAY AND SATURDAY.

THE MODELS HAVE NOT HAD STRONG CONTINUITY IN THE LAST 24 HOURS WITH
THE LARGE SCALE FEATURES OVER OUR AREA...SO FORECAST CONTINUITY
BEYOND SUNDAY IS SOMEWHAT QUESTIONABLE. COOLING SEEN IN MEX
GUIDANCE FOR MONDAY AND TUESDAY MAY BE A LITTLE OVERDONE...SO...WHILE
LOWERING FORECAST TEMPS FOR THAT PERIOD...WILL NOT GO QUITE AS LOW
AS MEX GUIDANCE. 35
&&

.AVIATION...
BIGGEST CONCERN IN THE FIRST 6-8 HRS WILL BE CONVECTION. ISLTD TO
SCT CONVECTION WILL CONTINUE TO DEVELOP/MOVE ALONG A WEAK BOUNDARY
STRETCHING FROM POE TWRDS GPT. OUTSIDE OF THAT VFR CONDITIONS WILL
REMAIN IN PLACE UNTIL AFTER MIDNIGHT. AT THAT POINT MVFR CIGS AND
VISBIES WILL START TO DEVELOP WITH CIGS POSSIBLY DOWN TO 1500 FT.
VISBIES SHOULD MAINLY REMAIN ABV 4SM. WINDS WILL GENERALLY BE
LIGHT AND VARIABLE THROUGH THE NIGHT AND INTO TOMORROW AS OUR WEAK
BOUNDARY MOVES INTO THE AREA AND THEN BECOMES DIFFUSE. /CAB/
&&

.MARINE...LIGHT AND VARIABLE WINDS WILL CONTINUE THROUGH THE NIGHT
AND EARLY TOMORROW BEFORE HIGH PRESSURE PUSHES OVER THE ERN SEABOARD
CAUING ONSHORE TO RETURN...PERSISTING THROUGH THE REST OF THE WEEK.
WINDS WILL GENERALLY REMAIN CALM BUT COULD APPROACH EXERCISE CAUTION
BY THE END OF THE WEEK. SEAS WILL ALSO MAINLY RANGE FROM 1-4FT.
/CAB/
&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  66  86  68  87 /  40  40  10  10
BTR  69  88  70  89 /  30  30  10  10
MSY  71  87  72  86 /  30  30  10  10
GPT  70  85  70  83 /  30  50  10  10

&&

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

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE NEW ORLEANS LA
328 PM CDT MON MAY 11 2009

GMZ530-550-555-570-575-LAZ034>040-046>050-056>070-MSZ068>071-077-
080>082-122030-
LAKE PONTCHARTRAIN AND LAKE MAUREPAS-
COASTAL WATERS FROM THE SOUTHWEST PASS OF THE MISSISSIPPI RIVER
TO LOWER ATCHAFALAYA RIVER LA OUT 20 NM-
COASTAL WATERS FROM PASCAGOULA MS TO THE SOUTHWEST PASS OF THE
MISSISSIPPI RIVER OUT 20 NM-
COASTAL WATERS FROM THE SOUTHWEST PASS OF THE MISSISSIPPI RIVER
TO LOWER ATCHAFALAYA RIVER LA FROM 20 TO 60 NM-
COASTAL WATERS FROM PASCAGOULA MS TO THE SOUTHWEST PASS OF THE
MISSISSIPPI RIVER FROM 20 TO 60 NM-POINTE COUPEE-WEST FELICIANA-
EAST FELICIANA-ST. HELENA-TANGIPAHOA-WASHINGTON-ST. TAMMANY-
IBERVILLE-WEST BATON ROUGE-EAST BATON ROUGE-ASCENSION-LIVINGSTON-
ASSUMPTION-ST. JAMES-ST. JOHN THE BAPTIST-UPPER LAFOURCHE-
ST. CHARLES-UPPER JEFFERSON-ORLEANS-UPPER PLAQUEMINES-
UPPER ST. BERNARD-UPPER TERREBONNE-LOWER TERREBONNE-
LOWER LAFOURCHE-LOWER JEFFERSON-LOWER PLAQUEMINES-
LOWER ST. BERNARD-WILKINSON-AMITE-PIKE-WALTHALL-PEARL RIVER-
HANCOCK-HARRISON-JACKSON-
328 PM CDT MON MAY 11 2009

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF COASTAL WATERS
OF SOUTHEAST LOUISIANA AND SOUTH MISSISSIPPI...SOUTHEAST
LOUISIANA AND SOUTHERN MISSISSIPPI.

.DAY ONE...THIS EVENING AND OVERNIGHT
SCATTERED THUNDERSTORMS WILL CONTINUE TO DEVELOP DURING THE EARLY
EVENING HOURS. A FEW STORMS MAY BECOME SEVERE WITH HAIL AND
DAMAGING WINDS. THE MAIN THREAT AREA WILL BE WEST OF A LINE FROM
MCCOMB...TO BATON ROUGE...TO PLAQUEMINE...WHERE A SEVERE
THUNDERSTORM WATCH WILL BE IN EFFECT UNTIL 8 PM CDT.

RIVER FLOODING...MINOR RIVER FLOODING WILL CONTINUE ON THE
MISSISSIPPI RIVER AT RED RIVER LANDING. PLEASE REFER TO THE
LATEST RIVER FLOOD STATEMENT FOR DETAILS.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY
THE MISSISSIPPI RIVER IS EXPECTED TO RISE ABOVE FLOOD STAGE AT
BATON ROUGE ON THURSDAY MAY 14TH...AND CONTINUE ABOVE FLOOD STAGE
AT RED RIVER LANDING. PLEASE REFER TO THE LATEST RIVER FLOOD STATEMENTS
FOR DETAILS.

.SPOTTER INFORMATION STATEMENT...
SPOTTERS OBSERVING ANY SEVERE WEATHER SHOULD PASS ON ANY REPORTS
TO THE NATIONAL WEATHER SERVICE.

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