Severe Thunderstorm Warning 44, NWS New Orleans, LA

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE NEW ORLEANS/BATON ROUGE LA
520 PM CDT FRI APR 30 2004

.UPDATED DISCUSSION...
HAVE GROWING CONCERNS ABOUT REDEVELOPING RAINS WITH BACKWARD
PROPAGATION CHARACTERISTICS OVERNIGHT. OVERALL SYNOPTIC PATTERN
WOULD SUPPORT A RETURN TO MODERATE ONSHORE FLOW IN RESPONSE TO LOW
LEVEL JET DEVELOPING WITH APPROACHING SHORT-WAVE. THIS WILL INCREASE
UPPER DIVERGENCE IN AN UNSTABLE AIRMASS AS WATER VAPOR IMAGERY SHOWS
SYNOPTIC SCALE DRY AIR ALOFT OVER INCREASING DEWPOINT AIR. A
MESOHIGH OVER LAKE PONTCHARTRAIN WITH A VERY WELL PRONOUNCED OUTFLOW
BOUNDARY EXTENDING FROM FORT WALTON BEACH FLORIDA TO NEAR CAMERON
LOUISIANA WILL SERVE AS AN OVERRUNNING BOUNDARY IN THE SHORT-TERM
BEFORE DISSOLVING IN FAVOR OF LOW LEVEL MARITIME FLOW. END RESULT
WILL LIKELY BE FLOODING RAINS REDEVELOPING.

WILL NOT UPDATE ZONES JUST YET. PLAN ON REVIEWING THE 00Z KSIL
SOUNDING AND RUN LOCAL QPF SCHEMES ON IT. IF IT SUPPORTS ADDITIONAL
HEAVY RAINFALL...THEN ANTICIPATE AN UPDATE TO ALL PRODUCTS BEFORE 9
PM ALONG WITH A POSSIBLE AREAL EXTENSION OF THE FLOOD WATCH FOR
TONIGHT. THIS IS AN UNEASY SITUATION AND WILL HAVE TO BE WATCHED
CLOSELY. WILL UPDATE THIS DISCUSSION AFTER REVIEW OF SOUNDING PRIOR
TO ANY UPDATES...PROBABLY AROUND 8 PM.

&&

.PREV DISCUSSION...ETA AND AVN MODELS IN GOOD AGREEMENT WITH
MOVEMENT OF SHORT WAVE THRU THE CWA THIS EVENING. SATELLITE SHOWS
DEVELOPMENT OF MODERATE CONVECTION ALONG RIGHT REAR QUADRANT OF 50
KT JETLET OVER WESTERN PORTION OF CWA. ETA DRAGS THIS JET EAST
NORTHEAST AFTER 00Z. WILL KEEP THREAT OF HEAVY RAINFALL NORTH OF THE
LAKE TONIGHT. HEAVY RAINS PREDOMINATED SOUTH OF LAKE PONTCHARTRAIN
THIS MORNING AND INTO NOO HOURS...COOLING OFF THE AIRMASS AND
STABILIZING THE AIRMASS SOMEWHAT. ARISHE IN WESTERN PART OF CWA HAD
A CHANCE TO WARM UP AND BECOME MORE UNSTABLE. CONVECTION OS NOW
DEVELOPED IN THE WARMER SECTOR AS OUTFLOW BOUNDARY FROM COOLER
SECTOR SOUTH OF THE LAKE INTERACTS WITH OUTFLOW BOUNDARIES FROM
CONVECTION OVER CENTRAL LA. WILL FOCUS ON THIS AREA FOR ADDITIONAL
FLOOD WARNING/URBAN FLOOD ADVISORIES THIS AFTERNOON/EVENING. PERIOD.
AS SHORT WAVE SHIFTSEAST DRIER AIR WILL MOVE IN CAPPING OFF
CONVECTION TONIGHT AND IN THE MORNING.
NEXT SHOT OF CONVECTION WILL BE SATURDAY AFTERNOON AHEAD OF COLD
FRONT. SOME THREAT OF SEVERE THUNDERSTORMS LATE SATURDAY AS WE CME
UNDER RIGHT REAR QUAD OF 80 KT JET ABOUT 00Z. NO CLEARING UNTIL
MONDAY THOUGH. SURFACE FRONT WILL DRAG THRU THE AREA SUNDAY MORNING,
BUT EXPECT OVERRUNNING PATTERN UNTIL SUNDAY NIGHT.
IN MARINE...STILL LOOKS GOOD FOR SMALL CRAFT ADVISORY SUNDAY NIGHT
THROUGH MONDAY. WILL UPDATE FLOOD WATCH LATER TO REDUCE AREA FOR
TONIGHT.

&&

.PRELIMINARY POINT TEMP/POPS...
MCB 66 79 61 72 / 30 70 70 70
BTR 67 80 63 73 / 30 60 70 80
MSY 68 81 66 74 / 20 60 70 80
GPT 68 80 66 75 / 30 40 70 80

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...FLOOD WATCH NORTH OF LAKE PONTCHARTRAIN
MS...NONE
SE LA AND MS COASTAL WATERS...NONE.

&&

24

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE NEW ORLEANS LA
1030 AM CDT FRI APR 30 2004

GMZ530-LAZ034>040-046>050-056>070-MSZ068>071-077-080>082-011100-
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-
1030 AM CDT FRI APR 30 2004

THIS HAZARDOUS WEATHER OUTLOOK IS FOR EAST CENTRAL AND SOUTHEAST
LOUISIANA AND EXTREME SOUTHWEST AND SOUTH CENTRAL MISSISSIPPI.

.DAY ONE...THIS AFTERNOON AND TONIGHT

THUNDERSTORMS...
SCATTERED TO NUMEROUS THUNDERSTORMS ARE EXPECTED TO DEVELOP AND
TRAIN ACROSS THE AREA THIS AFTERNOON AND THIS EVENING BEFORE
DIMINISHING OVERNIGHT. THE MAIN THREAT FROM THE THUNDERSTORMS WILL
BE LOCALLY HEAVY RAINFALL. IN ADDITION TO THE HEAVY RAINFALL
THREAT...THE STRONGER THUNDERSTORMS WILL BE CAPABLE OF PRODUCING
FREQUENT LIGHTNING...GUSTY WINDS...AND SMALL HAIL. ISOLATED SEVERE
THUNDERSTORMS ARE ALSO POSSIBLE.

A FLOOD WATCH IS IN EFFECT FOR SOUTH CENTRAL...SOUTH EASTERN
LOUISIANA AND SOUTHERN MISSISSIPPI FOR THIS AFTERNOON AND TONIGHT.
RAINFALL AMOUNTS OF 3 TO 5 INCHES ARE POSSIBLE FROM THUNDERSTORMS AS
AN UPPER LEVEL LOW PRESSURE TROUGH MOVES EAST AND OVER THE AREA.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

THUNDERSTORMS...
SCATTERED TO NUMEROUS THUNDERSTORMS ARE EXPECTED SATURDAY AND
SUNDAY. THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS CAPABLE OF
PRODUCING DAMAGING WINDS AND LARGE HAIL SATURDAY AFTERNOON AND
SATURDAY NIGHT.

MARINE...
SMALL CRAFT ADVISORY CONDITIONS ARE EXPECTED TO DEVELOP SUNDAY AND
CONTINUE MONDAY AS NORTHERLY WINDS INCREASES IN THE WAKE OF A COLD
FRONT.

.SPOTTER INFORMATION STATEMENT...

THE ACTIVATION OF STORM SPOTTERS...HAM RADIO OPERATORS AND EMERGENCY
MANAGEMENT PERSONNEL...IN SUPPORT OF SEVERE WEATHER OPERATIONS...IS
NOT REQUESTED AT THIS TIME.

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE NEW ORLEANS LA
407 PM CDT FRI APR 30 2004

..TIME...   ...EVENT...     ...CITY LOCATION...      ...LAT.LON...
..DATE...   ....MAG....     ..COUNTY LOCATION...ST.. ...SOURCE....
            ..REMARKS..

0128 PM     FLASH FLOOD      LIVONIA                 30.56N 91.55W
04/30/2004                   POINTE COUPEE      LA   LAW ENFORCEMENT

            STREET FLOODING AND FLOODING OF A FEW ROADS FROM FORDOCHE
            TO LIVONIA TO ERWINVILLE ON HIGHWAYS 77, 78, 977, AND
            190.

0940 AM     FLASH FLOOD      LAROSE                  29.57N 90.37W
04/30/2004                   LAFOURCHE          LA   LAW ENFORCEMENT

            FEW HOMES FLOODED FROM LAROSE TO GALLIANO TO GOLDEN
            MEADOW AND CUTOFF. FEW SIDE ROADS ALSO FLOODED. RAIN
            GAUGE IN LAROSE MEASURED 12 INCHES OF RAIN WHICH MATCHED
            KLIX RADAR RAINFALL ESTIMATES.

&&

TD