Severe Thunderstorm Warning 82, NWS New Orleans, LA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
336 PM CDT FRI MAY 13 2011

.SHORT TERM...
SCATTERED STRONG TO LOCALLY SEVERE THUNDERSTORMS OVER EAST PORTION
OF THE FORECAST AREA EAST OF I-55 CONTINUES TO MOVE EASTWARD AS UPPER
VORT LOBE ROTATES EASTWARD AND OUT OF AREA. WILL HOLD ONTO SLIGHT
CHANCE THUNDERSTORMS MOST AREAS INTO THE EVENING WITH LOW END
CHANCE CATEGORY OVER THE MISSISSIPPI COAST. SOME THREAT OF
ISOLATED TO SCATTERED CONVECTION STILL EXISTS INTO EVENING HOURS
AS SURFACE BOUNDARY OVER CENTRAL LOUISIANA FINALLY MOVES THROUGH
REGION. COOLER AND DRIER AIRMASS BEGINS TO MOVE INTO REGION AFTER
MIDNIGHT. RELATIVELY COOL AND DRY WEATHER SHOULD DOMINATE REGION
SATURDAY THROUGH MID WEEK AS UPPER TROUGH REMAINS CENTERED OVER
THE EAST PORTION OF U.S. SEVERAL VORT LOBES ROTATING THROUGH UPPER
TROUGH WILL PROVIDE UPPER SUPPORT TO BRING ADDITIONAL RE ENFORCING
SURFACE AND COOLER DRIER AIR TO MOVE INTO REGION.

LONG TERM...
BOTH ECMWF AND GFS FORECASTING SIGNIFICANT UPPER TROUGH OR CLOSED
LOW TO MOVE INTO THE CO/NM REGION LATE NEXT WEEK WITH SURFACE
CYCLOGENISIS IN THE PLAINS. THIS DEVELOPMENT SHOULD ALLOW
MOISTURE TO STREAM NORTHWARD WITH A CHANCE OF PRECIPITATION LATE
NEXT WEEK.  21

&&

.AVIATION...
ONCE CONVECTION CLEARS EASTERN TERMINALS IN NEXT HOUR OR SO...VFR
CONDITIONS EXPECTED THROUGH THE PERIOD. GUSTY WINDS IN EXCESS OF 20
KNOTS POSSIBLE AT KNEW AFTER COLD FRONTAL PASSAGE AFTER 10Z. 35

&&

.MARINE...
AFTER FRONTAL PASSAGE TONIGHT...OFFSHORE FLOW WILL DOMINATE THE MARINE
AREA THROUGH MID WEEK. THE FRONTAL PASSAGE ACROSS THE GULF WATERS
SATURDAY MORNING WILL BRING AN INCREASE TO MODERATE LEVELS AND
SEAS BUILDING TO 4 FEET IN OUTER WATERS INTO SUNDAY. WILL
INTRODUCE SMALL CRAFT EXERCISE CAUTION LATE TONIGHT INTO SATURDAY
MORNING AS COOL DRY AIR IN NORTHWEST FLOW CREATES GUSTY NORTHWEST
WINDS 15 TO 20 KT. WINDS SHOULD DIMINISH SOMEWHAT SATURDAY
AFTERNOON. A REENFORCING SURGE OF COOLER AIR MAY PROMPT SMALL
CRAFT ADVISORIES MONDAY NIGHT INTO EARLY TUESDAY MORNING.

&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  57  78  54  77 /  20  10  10  10
BTR  60  80  55  80 /  20  10  10  10
ASD  63  81  56  80 /  20  10  10  10
MSY  67  80  61  79 /  20  10  10  10
GPT  65  82  58  80 /  30  10  10  10
PQL  65  82  57  80 /  30  10  10  10

&&

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

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE NEW ORLEANS LA
652 PM CDT FRI MAY 13 2011

GMZ530-532-534-536-538-550-552-555-557-570-572-575-577-LAZ034>040-
046>050-056>070-MSZ068>071-077-080>082-150000-
LAKE PONTCHARTRAIN AND LAKE MAUREPAS-MISSISSIPPI SOUND-
LAKE BORGNE-CHANDELEUR SOUND-BRETON SOUND-
COASTAL WATERS FROM PORT FOURCHON TO LOWER ATCHAFALAYA RIVER OUT
20 NM-
COASTAL WATERS FROM THE SOUTHWEST PASS OF THE MISSISSIPPI RIVER
TO PORT FOURCHON OUT 20 NM-
COASTAL WATERS FROM BOOTHVILLE LA TO THE SOUTHWEST PASS OF THE
MISSISSIPPI RIVER OUT 20 NM-
COASTAL WATERS FROM PASCAGOULA MS TO STAKE ISLAND LA OUT 20 NM-
COASTAL WATERS FROM PORT FOURCHON TO LOWER ATCHAFALAYA RIVER FROM
20 TO 60 NM-
COASTAL WATERS FROM THE SOUTHWEST PASS OF THE MISSISSIPPI RIVER
TO PORT FOURCHON FROM 20 TO 60 NM-
COASTAL WATERS FROM STAKE ISLAND LA TO THE SOUTHWEST PASS OF THE
MISSISSIPPI RIVER FROM 20 TO 60 NM-
COASTAL WATERS FROM PASCAGOULA MS TO STAKE ISLAND LA 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-
652 PM CDT FRI MAY 13 2011

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

.DAY ONE...TONIGHT
ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS WILL CONTINUE TO
BE POSSIBLE THROUGH TONIGHT. A FEW THUNDERSTORMS COULD BE STRONG
OR SEVERE WITH THE MAIN THREAT BEING LARGE HAIL. STRONG WIND GUSTS
OF 40 TO 50 MPH AND FREQUENT CLOUD TO GROUND LIGHTNING WILL ALSO
BE POSSIBLE.

FOLLOWING THE COLD FRONT PASSAGE...WINDS WILL TURN TO THE
NORTHWEST AND INCREASE TO 15 TO 20 KNOTS OVER THE COASTAL WATERS.
AN EXERCISE CAUTION HEADLINE IS IN EFFECT FOR ALL COASTAL WATERS
FROM 10 PM TONIGHT THROUGH 10 AM SATURDAY MORNING.

THE MISSISSIPPI AND ATCHAFALAYA RIVERS REMAIN ABOVE FLOOD STAGE
AT SEVERAL FORECAST POINTS. PLEASE REFER TO THE LATEST FLOOD
WARNINGS AND STATEMENTS FOR DETAILS.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY
FLOOD WARNINGS ARE IN EFFECT FOR SEVERAL POINTS ALONG THE
MISSISSIPPI AND ATCHAFALAYA RIVERS. PLEASE REFER TO THE LATEST
FLOOD WARNINGS AND STATEMENTS FOR DETAILS.

.SPOTTER INFORMATION STATEMENT...
SPOTTER ACTIVATION IS NOT ANTICIPATED AT THIS TIME...BUT REPORTS
OF SEVERE WEATHER SHOULD BE FORWARDED TO THE NATIONAL WEATHER
SERVICE.

95/DM

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE NEW ORLEANS LA
551 PM CDT FRI MAY 13 2011

LAZ038-040-050-058-060>062-140700-
TANGIPAHOA-ST. TAMMANY-LIVINGSTON-ST. JOHN THE BAPTIST-
ST. CHARLES-UPPER JEFFERSON-ORLEANS-
INCLUDING THE CITIES OF...HAMMOND...PONCHATOULA...SLIDELL...
MANDEVILLE...COVINGTON...LACOMBE...DENHAM SPRINGS...WALKER...
LAPLACE...RESERVE...DESTREHAN...NORCO...METAIRIE...KENNER...
NEW ORLEANS
551 PM CDT FRI MAY 13 2011

...LAKE PONTCHARTRAIN WATER LEVELS EXPECTED TO RISE DUE TO BONNET
CARRE SPILLWAY OPENING...

LAKE PONTCHARTRAIN WATER LEVELS ARE EXPECTED TO BECOME ELEVATED
APPROXIMATELY 1 TO 2.5 FEET ABOVE NORMAL DURING THE NEXT WEEK DUE
TO THE OPENING OF THE BONNET CARRE SPILLWAY...WHICH DIVERTS WATER
FROM THE MISSISSIPPI RIVER INTO THE LAKE. THE FORECAST OF ELEVATED
WATER LEVELS IS BASED ON ANALYSIS OF TIDE GAGES AROUND LAKE
PONTCHARTRAIN DURING SEVERAL PREVIOUS OPENINGS OF THE SPILLWAY
SINCE THE 1970S.

CURRENT TIDE LEVELS ARE NEAR NORMAL ACROSS MOST OF THE LAKE...BUT
SLIGHT INCREASES HAVE ALREADY BEEN NOTED AT SOME OF THE GAGES.

CURRENT REPRESENTATIVE READINGS INCLUDE:
COE MANDEVILLE TIDE GAGE 1.00 FT NAVD88
COE WEST END - NEW ORLEANS GAGE 0.50 FT NAVD88

IMPACTS SHOULD BE MINIMAL WITH ONLY MINOR FLOODING OF MARSHLAND
AND POSSIBLY SOME LOW LYING SECONDARY ROADWAYS...PRIMARILY ON THE
NORTH SHORE. HOWEVER...LAKE PONTCHARTRAIN WATER LEVELS ARE
SENSITIVE TO PROLONGED PERIODS OF SOUTH OR SOUTHEAST WINDS. IF A
PROLONGED PERIOD OF STRONG SOUTHEAST OR SOUTH WINDS DEVELOP...
WATER LEVELS MAY BECOME MORE ELEVATED THAN CURRENTLY FORECAST...
REACHING 2 TO 3 FEET ABOVE NORMAL.

RESIDENTS IN LOW LYING AREAS AROUND LAKE PONTCHARTRAIN SHOULD
CONTINUE TO MONITOR WATER LEVELS AND LISTEN FOR ANY COASTAL FLOOD
STATEMENTS OR WARNINGS THAT MAY BE ISSUED AT A LATER DATE.

DM/FR

LAZ034-035-140115-

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE NEW ORLEANS LA
712 PM CDT FRI MAY 13 2011

...STRONG THUNDERSTORM MOVING EAST AFFECTING POINTE COUPEE PARISH...
WEST FELICIANA PARISH...

AT 708 PM CDT...NATIONAL WEATHER SERVICE METEOROLOGISTS DETECTED A
STRONG THUNDERSTORM 8 MILES EAST OF SIMMESPORT...OR ABOUT OVER
LETTSWORTH...MOVING EAST AT 15 MPH.

THE STRONG THUNDERSTORM WILL AFFECT AREAS IN AND AROUND...
BATCHELOR...MORGANZA...WAKEFIELD...ST. FRANCISVILLE...SPILLMAN AND
NEW ROADS

THE PRIMARY THREATS FROM THIS STORM 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 THIS STORM HAS PASSED.

THIS STORM COULD PRODUCE RAINFALL AMOUNTS OF ONE TO TWO INCHES IN A
SHORT PERIOD OF TIME...QUICKLY RESULTING IN PONDING OF WATER AS
WATER HAS NOWHERE TO RUN OFF TO. REMEMBER...DO NOT DRIVE YOUR
VEHICLE INTO WATER COVERED ROADWAYS. THE DEPTH MAY BE TOO GREAT TO
ALLOW A SAFE CROSSING.

FREQUENT LIGHTNING IS OCCURRING WITH THIS STORM. IF OUTDOORS...STAY
AWAY FROM ISOLATED HIGH OBJECTS SUCH AS TREES. MOVE INDOORS IF
POSSIBLE. WHEN INDOORS...STAY AWAY FROM WINDOWS AND DOORS AND AVOID
USING TELEPHONES UNLESS IT IS AN EMERGENCY. TRY TO UNPLUG UNNECESSARY
ELECTRICAL APPLIANCES BEFORE THE THUNDERSTORM APPROACHES.

CAB

LAZ034>036-140230-

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE NEW ORLEANS LA
829 PM CDT FRI MAY 13 2011

...STRONG THUNDERSTORM MOVING EAST AFFECTING POINTE COUPEE PARISH...
EAST FELICIANA PARISH...WEST FELICIANA PARISH...

AT 826 PM CDT...NATIONAL WEATHER SERVICE METEOROLOGISTS DETECTED A
STRONG THUNDERSTORM 6 MILES WEST OF ST. FRANCISVILLE...MOVING EAST AT
20 MPH.

THE STRONG THUNDERSTORM WILL AFFECT AREAS IN AND AROUND...ST.
FRANCISVILLE AND JACKSON

THE PRIMARY THREATS FROM THIS STORM ARE FREQUENT LIGHTNING...PEA TO
DIME SIZE HAIL...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 THIS STORM HAS PASSED.

THIS STORM COULD ALSO PRODUCE RAINFALL AMOUNTS OF OVER ONE INCH IN A
SHORT PERIOD OF TIME...RESULTING IN PONDING OF WATER AROUND LOW
LYING ROADWAYS...ESPECIALLY NEAR THE RIVER WHERE THE GROUND IS
SATURATED DUE TO HIGH RIVER LEVELS. REMEMBER...DO NOT DRIVE YOUR
VEHICLE INTO WATER COVERED ROADWAYS. THE DEPTH MAY BE TOO GREAT TO
ALLOW A SAFE CROSSING.

95/DM

LAZ037-038-050-140300-

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE NEW ORLEANS LA
901 PM CDT FRI MAY 13 2011

...STRONG THUNDERSTORM MOVING SOUTHEAST AFFECTING ST. HELENA
PARISH...LIVINGSTON PARISH...TANGIPAHOA PARISH...

AT 858 PM CDT...NATIONAL WEATHER SERVICE METEOROLOGISTS DETECTED A
STRONG THUNDERSTORM 11 MILES NORTHEAST OF DENHAM SPRINGS...OR ABOUT 7
MILES EAST OF WATSON...MOVING SOUTHEAST AT 25 MPH.

THE STRONG THUNDERSTORM WILL AFFECT AREAS IN AND AROUND...
MONTPELIER...LIVINGSTON...TICKFAW...SPRINGFIELD...HAMMOND AND
PONCHATOULA

THE PRIMARY THREATS FROM THIS STORM ARE FREQUENT LIGHTNING...SUB
SEVERE HAIL UP TO NICKEL SIZE...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 THIS STORM HAS PASSED.

THIS STORM COULD PRODUCE RAINFALL AMOUNTS OF OVER ONE INCH IN A
SHORT PERIOD OF TIME...RESULTING IN PONDING OF WATER AROUND LOW
LYING ROADWAYS. REMEMBER...DO NOT DRIVE YOUR VEHICLE INTO WATER
COVERED ROADWAYS. THE DEPTH MAY BE TOO GREAT TO ALLOW A SAFE
CROSSING.

95/DM