Severe Thunderstorm Warning 19, NWS New Orleans, LA

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE NEW ORLEANS/BATON ROUGE LA
630 AM CST WED MAR 12 2003

12Z LIX SOUNDING SHOWED A PRECIPITABLE WATER VALUE NEAR 1.4
INCHES...LIFTED INDEX OF MINUS 3...CAPE VALUE NEAR 500 J/KG AND
VIRTUALLY NO CAP TO INHIBIT CONVECTION. LIX RADAR REVEALED SCATTERED
LIGHT SHOWERS AROUND THE TIDAL LAKES AND MISSISSIPPI COAST. WILL
UPDATE ZONES TO INCREASE POPS FOR SOUTH AND EAST ZONES.

PREVIOUS DISCUSSION:

LATEST SURFACE ANALYSIS CONTINUE TO SHOW A 1022MB HIGH OVER THE MID
ATLANTIC STATES WITH THE RIDGE AXIS SOUTHWEST THROUGH THE CENTRAL
GULF COAST. DEWPOINT READINGS WERE MAINLY IN THE 50S ACROSS THE
FORECAST AREA WITH NEAR 60F SOUTH OF THE LAKE AND ALONG THE COAST.
LATEST LIX SOUNDING REVEALED A LIGHT SOUTHEAST WINDS BELOW THE
BOUNDARY LAYER. VAD WIND PROFILE SHOWED A DEEP SOUTHERLY FLOW AT
09Z. LIX SOUNDING SHOWED A PRECIPITABLE WATER VALUE AROUND 0.7
INCH...1.5 INCHES WAS NOTED OVER CRP WITH THE MOISTURE AXIS NORTH TO
FWD WITH 0.8 INCH. A GENERAL ZONAL/NW FLOW WAS LOCATED ACROSS THE
NORTH TIER CONUS WITH A WEAKER ZONAL FLOW OVER THE SOUTHERN TIER
CONUS. SUBTROPICAL JET WAS   DISPLACED OVER THE GULF AND FLORIDA.

SHORT RANGE MODELS INITIALIZED WELL. GFS SOLUTIONS CONTINUE TO BE
STRONGER THAN ETA AND NGM WITH THE AMPLIFICATION OF THE RIDGE. IN
ADDITION...GFS PRECIPITABLE WATERS VALUE INCREASES TO 1.7 INCHES
OVER MSY BY 18Z TODAY WHILE ETA AND NGM ARE AROUND 1.3 INCHES. 08Z
RADAR IMAGE WAS SHOWING SCATTERED LIGHT SHOWERS OVER ATCHAFALAYA
BAY. WILL HEDGE TOWARD HIGHER POPS ALONG THE LOUISIANA COAST. GFS
SHOWED A PW VALUE OF 1.2 INCHES OVER MCB AT THE SAME TIME. UPPER
LEVEL DISTURBANCE OVER WEST TEXAS IS EXPECTED TO APPROACH WEST
LOUISIANA BY 00Z THU. GFS INCREASE MOISTURE ACROSS THE REST OF THE
FORECAST AREA BY 00Z WHILE NGM AND ETA REMAINS THE SAME FROM 18Z WED
TO 00Z THU. WILL HEDGE A LITTLE HIGHER WITH POPS ACROSS THE FORECAST
AREA...BUT NOT AS HIGH AS GFS. IN THE NORTHERN STREAM...A SHORT WAVE
JUST EAST OF THE RIDGE AXIS WILL TRACK SOUTHEAST ACROSS THE
NORTHEAST CONUS. GFS AND ETA SOMEWHAT WILL TRY TO PUSH THE
ASSOCIATED VORT LOBE SOUTH ACROSS THE NORTH CENTRAL GULF REGION LATE
THURSDAY INTO FRIDAY. ASSOCIATED SURFACE LOW WILL PUSH A COLD FRONT
THROUGH AREA EARLY FRIDAY. THIS PATTERN IS SIMILAR TO THE GFS RUNS
48 HOURS AGO. WILL CONTINUE POPS THROUGH SUNDAY. STRONG NORTHWEST
WINDS ARE EXPECTED TO SPREAD EAST ACROSS THE ROCKIES SUNDAY AND
SOUTH CENTRAL CONUS MONDAY AND TUESDAY. THAT PATTERN HAS NOT CHANGED
FROM RUN TO RUN YET. SO DRY MONDAY AND EARLY TUESDAY. ANOTHER SYSTEM
IS EXPECTED TO APPROACH THE AREA LATE TUESDAY. WILL INSERT RAIN
CHANCES LATE TUESDAY.

IN THE SHORT TERM...PATCHY DENSE FOG LOOKS TO BE THE MAIN CONCERN
TONIGHT AS DEWPOINTS CLIMB BACK INTO THE 60S AIDED BY A PERSISTENT
SOUTHERLY FLOW.

HERE ARE SOME NUMBERS TO PONDER...

MCB EE 076/059 079/059 076 434
BTR EE 075/061 079/060 076 334
MSY EE 075/062 079/062 075 534
GPT EE 075/061 075/061 075 534=

.NEW...NONE
LA...NONE.
MS...NONE.

18

LAZ034>040-046>050-056>070-MSZ068>071-077-080>082-131130-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE NEW ORLEANS LA
1119 AM CST WED MAR 12 2003

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHEAST LOUISIANA AND
EXTREME SOUTHWEST AND COASTAL MISSISSIPPI.

.DAY ONE...TODAY AND TONIGHT
THERE IS A SLIGHT CHANCE OF SEVERE THUNDERSTORMS THIS AFTERNOON AND
TONIGHT. THE PRIMARY THREAT WILL BE LARGE HAIL AND HEAVY RAINS FROM
SCATTERED THUNDERSTORMS THAT DEVELOP FROM THE COMBINATION OF DAYTIME
HEATING AND INCREASING HIGH DEWPOINT AIR EXCITED BY AN UPPER LEVEL
DISTURBANCE. THE AREA OF GREATEST RISK WILL BE SOUTH AND EAST OF
LINE OF I-55 FROM LUMBERTON TO SLIDELL TO THE LOWER ATCHAFALAYA
RIVER. AREAS OF EAST-CENTRAL LOUISIANA AND SOUTHWEST MISSISSIPPI
APPEARS TO HAVE LESS OF A RISK OF SEVERE STORMS AT THIS TIME. THIS
THREAT WILL CONTINUE INTO THE NIGHT WITH PERSISTENT HEAVY RAINFALL
FROM TRAIN EFFECT THUNDERSTORMS BECOMING PROBABLE MAINLY ALONG THE
MISSISSIPPI GULF COAST AND LOWER SOUTHEAST LOUISIANA.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUEDAY
THERE WILL BE AN ONGOING THREAT OF HEAVY RAINFALL AND SEVERE
THUNDERSTORMS THURSDAY THROUGH FRIDAY. CONDITIONS SHOULD IMPROVE
FOR SATURDAY BUT WITH A RISK OF DENSE FOG DEVELOPMENT EACH LATE
NIGHT AND EARLY MORNING.

THERE WILL BE AN INCREASING RISK OF THUNDERSTORMS WITH A HEAVY RAIN
AND FLOOD POTENTIAL DEVELOPING TUESDAY INTO TUESDAY NIGHT. MORE
DETAILS WILL BE FORTHCOMING IN FUTURE OUTLOOKS.

.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. IN THE EVENT OF HAIL STORM
DEVELOPMENT...THE NWS IS REQUESTING ALL FIRST RESPONSE AND LAW
ENFORCEMENT AGENCIES TO RELAY TIMELY REPORTS OF ANY HAIL STORMS
AFFECTING THEIR AREA.