Flash Flood Warning 15, NWS New Orleans, LA

AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE NEW ORLEANS LA
837 AM CDT THU MAY 14 2009

.UPDATE...
...SOUNDING DISCUSSION...

NO PROBLEMS WITH THE FLIGHT THIS MORNING. EXTREMELY MOIST SOUNDING
THIS MORNING THAT COULD BE CONFUSED WITH A PRECIPITATION LOADED
SOUNDING IF WE HAD ANY PRECIP IN THE AREA RIGHT NOW. PWATS ARE
1.82 AND THE LI IN IN THE -9 RANGE AGAIN THIS MORNING. SLIGHT
SURFACE INVERSION THIS MORNING WITH A LARGER CAP AROUND 800 MB. IF
THIS CAP CAN BREAK LATER IN THE DAY THERE ARE PLENTY OF THINGS IN
FAVOR OF SOME STRONG TO EVEN SEVERE THUNDERSTORM DEVELOPMENT. IN
ADDITION TO THE HIGH PWATS AND UNSTABLE LI...THE 500 MB TEMP IS
-12C...THE CAPE IS NEAR 3000 J/KG WITH PLENTY AVAILABLE IN THE
HAIL GROWTH ZONE...WHILE THE MID LEVEL LAPSE RATES ARE AT AROUND
7C/KM. WINDS REMAIN LIGHT AND VARIABLE FROM THE SURFACE THROUGH
400 MB SO THAT ANYTHING THAT DOES FORM WILL NOT BE IN A HURRY.

98/SO

&&

.PREV DISCUSSION... /ISSUED 425 AM CDT THU MAY 14 2009/

SHORT TERM...
SOME INTERESTING THINGS SHOWING UP IN ALL MODEL SUITES FROM THE
NORTH AMERICAN TO THE EUROPEAN. STARTING WITH THE SHORT TERM...A
WEAK TROPICAL WAVE IS MOVING WEST THROUGH THE GULF THIS MORNING
LOCATED ALONG 90WEST. THIS SHOULD HELP BRING SOME NOCTURNALS
ONSHORE THIS MORNING. THE FEATURE HAS ALSO INCREASED THE DEPTH OF
MOISTURE IN THE BOUNDARY LAYER. THIS WILL ADD TO THE RAIN CHANCES
FOR TODAY. RAIN CHANCES WILL GRADUALLY INCREASE EACH DAY AS
AVAILABLE MOISTURE INCREASES IN THE VERTICAL UNTIL THE FRONT
PASSES SUN NIGHT.

SH/TS WILL DEVELOP TODAY BY WAY OF A WELL DEVELOPED C-BRZ. DUE TO
THE INCREASED MOISTURE DEPTH PROVIDED BY THE WAVE...THE C-BRZ
SHOULD DEVELOP RATHER QUICKLY LATE THIS MORNING BECOMING THE
DOMINANT FORCING FEATURE. MICRO-ENVIRONMENT SHOWS THAT WE SHOULD
GET SOME ACTIVITY ALONG COASTAL LOCATIONS THROUGH MID-MORNING
WHILE INLAND GETS NEAR ZERO. DURING THE AFTERNOON WE SHOULD SEE
MORE ACTIVITY INLAND AND CLOSE TO ZERO ALONG COASTAL LOCATIONS.

WILL SEE INCREASED MOISTURE DEPTH EACH DAY SO FRI WHOULD RECEIVE A
FEW MORE SH/TS THAN TODAY ETC... LOOKS LIKE THE C-BRZ SHOULD GET
ACTIVATED EACH DAY UNTIL SUNDAY WHEN SUPPRESSION AHEAD OF THE
FRONT MAY WEAKEN THE FEATURE A LITTLE.

LONG TERM...
THE LONG WAVE TROUGH THAT WILL BE RESPONSIBLE FOR SUPPORTING THE
FRONTS MOVE THROUGH OUR AREA IS JUST NOW COMING INTO THE WEST
COAST AT VANCOUVER. AT THE SAME TIME...THE STRONG TROPICAL WAVE
MOVING THROUGH THE CARIBBEAN AT ABOUT 68.5W WILL GRADUALLY FIND
ITSELF IN THE EASTERN GULF AT THE SAME TIME THAT THE UPPER TROUGH
IS DIGGING OVER THE DEEP SOUTH. THE FLOW TO THE EAST OF THE UPPER
TROUGH WILL HELP EVACUATE THE NORTHERN PORTION OF THE WAVES COLUMN
CAUSING IT TO DEEPEN A LITTLE. THIS OCCURS WHILE THE MID/UPPER
LEVEL CUT OFF LOW THAT IS FORMING TRIES TO DEVELOP A WEAK SFC
REFLECTION AND WRAPS UNLIMITED MOISTURE AROUND ITS CIRCULATION.
THE FRONT SHOULD STALL OFFSHORE WHILE THIS OCCURS PROVIDING
SEVERAL DAYS OF SH/TS FOR AT LEAST THE COASTAL WATERS AND MAYBE
EVEN SOME ONSHORE LOCATIONS THROUGH MUCH OF NEXT WEEK.

AVIATION...
FOR 12Z ISSUANCE...MVFR CEILINGS AND VISIBILITIES WILL IMPACT THE
TAF SITES EARLY THIS MORNING BEFORE IMPROVING TO VFR CONDITIONS FOR
THE REMAINDER OF THE DAY. ISOLATED TO POSSIBLY SCATTERED CONVECTION
WILL THREATENED EACH TAF SITE DURING THE THE AFTERNOON HOURS...WITH
THE BEST CHANCES AT KMCB AND KGPT. AGAIN LATE TONIGHT AND EARLY
THURSDAY MORNING MVFR CEILINGS AND VISIBILITIES WILL BE
POSSIBLE...ESPECIALLY AT KMCB AND KBTR. 18

MARINE...
A SURFACE RIDGE WILL DOMINATE THE CENTRAL GULF COAST REGION THROUGH
THE END OF THE WEEK WITH GENERALLY LIGHT TO OCCASIONALLY MODERATE
ONSHORE FLOW PREVAILING. A COLD FRONT IS EXPECTED TO ENTER THE
COASTAL WATERS SUNDAY OR SUNDAY NIGHT. NORTH WINDS BEHIND THE
FRONTAL PASSAGE MAY PROMPT A SMALL CRAFT ADVISORY ON MONDAY. 18

&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  88  68  85  65 /  30  10  40  20
BTR  90  69  86  68 /  30  10  40  20
MSY  88  72  85  70 /  30  10  40  20
GPT  86  71  84  68 /  30  10  40  20

&&

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

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE NEW ORLEANS LA
1034 AM CDT THU MAY 14 2009

GMZ530-550-555-570-575-LAZ034>040-046>050-056>070-MSZ068>071-077-
080>082-151100-
PASCAGOULA TO SW PASS MISSISSIPPI RIVER OUT 20 NM-
PASCAGOULA TO SW PASS MISSISSIPPI RIVER 20-60 NM OUT-
SW PASS MISSISSIPPI RIVER TO ATCHAFALAYA RIVER OUT 20 NM-
SW PASS MISSISSIPPI RIVER TO ATCHAFALAYA RIVER 20-60 NM OUT-AMITE-
ASCENSION-ASSUMPTION-EAST BATON ROUGE-EAST FELICIANA-HANCOCK-
HARRISON-IBERVILLE-JACKSON-LAKES PONTCHARTRAIN AND MAUREPAS-
LIVINGSTON-LOWER JEFFERSON-LOWER LAFOURCHE-LOWER PLAQUEMINES-
LOWER ST BERNARD-LOWER TERREBONNE-ORLEANS-PEARL RIVER-PIKE-
POINTE COUPEE-ST CHARLES-ST HELENA-ST JAMES-ST JOHN THE BAPTIST-
ST TAMMANY-TANGIPAHOA-UPPER JEFFERSON-UPPER LAFOURCHE-
UPPER PLAQUEMINES-UPPER ST BERNARD-UPPER TERREBONNE-WALTHALL-
WASHINGTON-WEST BATON ROUGE-WEST FELICIANA-WILKINSON-
1034 AM CDT THU MAY 14 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 AFTERNOON AND TONIGHT

SCATTERED THUNDERSTORMS ARE EXPECTED TO DEVELOP THIS AFTERNOON
ACROSS SOUTHERN MISSISSIPPI AND SOUTHEAST LOUISIANA. SOME OF THESE
THUNDERSTORMS COULD BECOME STRONG WITH AN ISOLATED SEVERE
THUNDERSTORM POSSIBLE...PRODUCING LIGHTNING...HAIL...HEAVY
DOWNPOURS...AND GUSTY WINDS.

RIVER FLOODING...
MINOR RIVER FLOODING WILL CONTINUE ON THE MISSISSIPPI RIVER AT RED
RIVER LANDING. THE MISSISSIPPI RIVER IS EXPECTED TO RISE ABOVE
FLOOD STAGE AT BATON ROUGE TODAY. PLEASE REFER TO THE LATEST RIVER
FLOOD STATEMENTS FOR DETAILS.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

SCATTERED AFTERNOON THUNDERSTORMS WILL BE POSSIBLE THROUGH
SUNDAY. SOME OF THESE THUNDERSTORMS COULD BE STRONG TO POSSIBLY
SEVERE...PRODUCING LIGHTNING...HAIL...HEAVY DOWNPOURS...AND GUSTY
WINDS.

A COLD FRONT WILL AFFECT THE REGION SUNDAY AND SUNDAY NIGHT. SEVERAL
ROUNDS OF THUNDERSTORMS WILL DEVELOP ALONG AND AHEAD OF THE FRONT.
A FEW OF THESE THUNDERSTORMS COULD BECOME SEVERE...PRODUCING VERY
HEAVY RAINFALL...FREQUENT LIGHTNING...HAIL...AND DAMAGING WINDS.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL NOT BE NEEDED.

32

MSZ077-141830-

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE NEW ORLEANS LA
1237 PM CDT THU MAY 14 2009

...CLUSTER OF STRONG THUNDERSTORMS MOVING NORTHEAST AFFECTING PEARL
RIVER COUNTY...

AT 1236 PM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
CLUSTER OF STRONG THUNDERSTORMS 8 MILES WEST OF POPLARVILLE...OR
ABOUT 7 MILES EAST OF CROSSROADS...MOVING NORTHEAST AT 5 MPH.

THE CLUSTER OF STRONG THUNDERSTORMS WILL BE NEAR...
  POPLARVILLE BY 130 PM...

THE PRIMARY THREATS FROM THESE STORMS ARE FREQUENT LIGHTNING AND WIND
GUSTS TO NEAR 40 MPH...WHICH COULD DOWN TREE LIMBS AND BLOW AROUND
UNSECURED SMALL OBJECTS. SEEK SHELTER IN A SAFE HOME OR BUILDING
UNTIL THESE STORMS HAVE PASSED.

BANNAN