Severe Thunderstorm Warning 151, NWS New Orleans, LA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
412 AM CST WED NOV 21 2007

.SHORT TERM...
WEAK UPPER LEVEL DISTURBANCE ASSOCIATED WITH EXIT REGION OF JET
MAX THAT MOVED OUT OF NORTH MEXICO LAST NIGHT. THIS APPEARS TO BE
INDUCING ISENTROPIC LIFT ALONG A WARM FRONTOGENETIC ZONE. THIS
FEATURE IS MOVING RAPIDLY NORTHEAST AND SHOULD BE OUT OF THE
FORECAST AREA BEFORE SUNRISE. MOST RAIN AMOUNTS WERE IN THE 0.10
TO 0.50 INCH RAIN. BEYOND THIS FEATURE...THE REST OF THE MORNING
SHOULD BE ESSENTIALLY DRY AND MAY TAKE MAXIMUM DAYTIME HEATING AND
PERHAPS LAKE AND GULF BREEZE BOUNDARIES TO PROVIDE FOCUS TODAY.
COLD FRONT IS ON SCHEDULE TO MOVE THROUGH THE FORECAST AREA
OVERNIGHT AND SHOULD ARRIVE IN THE BATON ROUGE METRO AROUND
MIDNIGHT...CONTINUING THROUGH NEW ORLEANS METRO BY 3 AM AND
MISSISSIPPI GULF COAST BY 5 AM. CURRENT FRONTAL POSITION EXTENDS
FROM SPRINGFIELD MISSOURI TO NEAR ARDMORE OKLAHOMA AND MIDLAND-
ODESSA TEXAS AREA...MOVING SOUTHEAST AROUND 15 MPH. THE FRONT IS
DEPICTED WITH A 25 DEGREE F TEMPERATURE DROP WITHIN AN HOUR OF
PASSAGE BUT THIS SHOULD MODERATE SOME UPON ARRIVAL DOWN HERE.

RAN MODEL SOUNDINGS THROUGH CHAP PROGRAM FOR SEVERITY INDICATIONS.
THIS BEST THAT COULD BE MUSTERED WAS MARGINALLY STRONG WIND GUSTS
WITH CONVECTION IN THE 35 TO 45 MPH RANGE. OTHERWISE...ORGANIZED
SEVERE THUNDERSTORMS ARE NOT ANTICIPATED WITH THIS PARTICULAR
EVENT.

.LONG TERM...
MODELS CONTINUE TO SHOW A STRONGLY NEGATIVE TILT SYSTEM MOVING
ALONG OR BELOW 30N LATITUDE ACROSS NORTH MEXICO/TEXAS BEFORE
TURNING NORTHWARD OVER LOUISIANA MONDAY. THIS SYSTEM WILL LIKELY
PRODUCE SEVERE THUNDERSTORMS IN THE FORM OF A SQUALL LINE AND SOME
ROGUE SUPERCELLS FOR TORNADO DEVELOPMENT IF LOW LEVEL MOISTURE
BECOMES SURFACE BASED...AS IT APPEARS IT SHOULD. WIDESPREAD HEAVY
RAINS LOOK REASONABLE AS WELL WITH A TAP OF MOISTURE FROM THE
TROPICS TO FUEL THE SYSTEM. WILL NOT INCLUDE SEVERE WORDING IN
ZONES AT THIS TIME BUT WILL HIGHLIGHT IN HAZARDOUS WEATHER OUTLOOK
IN COORDINATION WITH STORM PREDICTION CENTER DAY 4-8 CONVECTIVE
OUTLOOK. STILL FEEL THERE MAY BE SOME TIMING DIFFERENCES...PERHAPS
LATER THAN MODEL INDICATED BUT MODELS HAVE ESTABLISHED SOME RUN-
TO-RUN CONSISTENCY THUSFAR WITH THIS WEEKEND/MONDAY SYSTEM.

&&

.AVIATION...
VFR CONDITIONS THIS MORNING WILL BE REDUCED TO MVFR CEILINGS LATER
THIS MORNING AND REMAINDER OF TODAY AND TONIGHT AT ALL CWA
TERMINALS. KMCB CURRENTLY HAS LIFR CEILING THAT MAY BE TEMPORARY
FOR THE NEXT HOUR OR TWO BEFORE BREAKING TO MVFR LEVELS. COLD
FRONTAL PASSAGE APPEARS TO BE AROUND 06Z AT KBTR AND KMCB...08Z
KMSY AND 0930-1000Z KGPT. LLWS CAN BE EXPECTED WITH THIS FRONTAL
PASSAGE IN THE LOWER 1KFT THURSDAY MORNING.

&&

.MARINE...
SMALL CRAFT ADVISORY WILL BE REQUIRED FOR THURSDAY AND FRIDAY AS
COLD AIR PUSHES INTO NORTH GULF.

&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  77  52  55  37 /  60  60  20  10
BTR  78  54  57  39 /  50  60  20  10
MSY  79  59  64  45 /  50  50  30  10
GPT  77  58  64  40 /  50  50  30  10

&&

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

24

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE NEW ORLEANS LA
205 PM CST WED NOV 21 2007

GMZ530-550-555-570-575-LAZ034>040-046>050-056>070-MSZ068>071-077-
080>082-221200-
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-
205 PM CST WED NOV 21 2007

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF GULF OF
MEXICO...SOUTHEAST LOUISIANA AND SOUTHERN MISSISSIPPI.

.DAY ONE...THIS AFTERNOON AND TONIGHT
SCATTERED THUNDERSTORMS WILL DEVELOP THIS AFTERNOON AND BECOME
MORE NUMEROUS TONIGHT IN ADVANCE OF AN APPROACHING STRONG COLD
FRONT. A FEW SEVERE THUNDERSTORMS WILL BE POSSIBLE THIS AFTERNOON
AND EVENING MAINLY ACROSS THOSE AREAS OF SOUTHWEST MISSISSIPPI AND
EAST CENTRAL LOUISIANA LOCATED TO THE WEST OF INTERSTATE 55 AND TO
THE NORTH OF INTERSTATES 10 AND 12. THE MAIN THREATS FROM ANY SEVERE
THUNDERSTORMS THAT DO DEVELOP WILL BE DAMAGING WINDS AND ISOLATED
TORNADOES.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY

THUNDERSTORMS WILL END WITH FRONTAL PASSAGE EARLY THURSDAY
MORNING. SMALL CRAFT ADVISORY CONDITIONS ARE EXPECTED OVER THE
COASTAL WATERS THURSDAY AND FRIDAY.

A LOW PRESSURE SYSTEM IS EXPECTED TO DEVELOP IN THE WEST GULF LATE
SATURDAY OR EARLY SUNDAY AND MOVE NORTHWARD INTO LOUISIANA AS A
STRONG STORM SYSTEM SUNDAY NIGHT AND EARLY MONDAY. SEVERE
THUNDERSTORMS ARE POSSIBLE FROM SUNDAY AFTERNOON INTO EARLY MONDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL NOT BE NEEDED TODAY. EMERGENCY MANAGERS ARE
URGED TO STAY ABREAST OF THE FORECASTS CONCERNING THE LOW PRESSURE
SYSTEM AND POSSIBLE SEVERE STORMS SUNDAY THROUGH MONDAY. IF THE
WEATHER PATTERN DEVELOPS AS INDICATED IN CURRENT WEATHER MODELS...
THEN A SIGNIFICANT SEVERE WEATHER EVENT MAY RESULT. ACTIVATION OF
STORM SPOTTERS AND EMERGENCY OPERATIONS MAY BE REQUIRED SUNDAY NIGHT
OR MONDAY.