Flash Flood Warning 23, NWS New Orleans, LA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
350 PM CDT TUE MAY 21 2013

.SYNOPSIS...
LATEST SURFACE SHOWED A DEEP 1001MB LOW OVER SOUTHWEST MINNESOTA
WITH AN OCCLUDED FRONT EXTENDING EAST THEN A COLD FRONT SOUTHWEST
THROUGH MISSOURI TO OKLAHOMA TO CENTRAL TEXAS. RIDGE OF HIGH
PRESSURE REMAINED FROM THE MID ATLANTIC STATES TO NORTHEAST GULF.
SOUTHWEST FLOW BETWEEN THESE TWO FEATURES ALLOW GULF MOISTURE TO
FUNNEL FROM THE TEXAS COAST TO THE GREAT LAKES REGION. UPPER LEVEL
ANALYSIS SHOWED THE CYCLONIC CIRCULATION CENTERED OVER THE SURFACE
LOW BUT EXPANSIVE OVER THE UPPER MISSISSIPPI VALLEY AND NORTHERN
PLAINS. IN ADDITION...IR SATELLITE IMAGERY SHOWED A SMALLER
CYCLONIC CIRCULATION OVER TEXAS PANHANDLE. PRECIPITABLE WATER
VALUE PLANAR FIELD SHOWED THE DEEP MOISTURE POOLING ALONG THE
FRONT WITH VALUES 1.5 INCHES FROM NORTHEAST TEXAS TO CENTRAL
ARKANSAS...PW VALUES FROM 1.5 INCHES NW ZONES TO 1 INCH OVER MS
COAST. ISOTACH ANALYSIS AT 250MB SHOWED JET MAX OF 95 KNOTS ON THE
FRONT SIDE OF THE MAIN UPPER LOW/TROUGH...NORTHERN MISSOURI TO
WISCONSIN AND SUB-JET FROM SOUTH TEXAS TO WEST CUBA...PLACE A
DIVERGENCE FIELD OVER THE ARKLATEX REGION. IN OTHER WORDS...BEST
FIELDS FOR CONVECTION WILL OCCUR NORTHWEST OF THE FORECAST AREA
THIS AFTERNOON.

&&

.DISCUSSION...
MAIN UPPER LEVEL LOW/TROUGH WILL FILL OR OPEN TO A POSITIVELY TILTED
TROUGH. THIS WILL ALLOW THE SMALLER CIRCULATION TO LIFT NORTHEAST
LATE TONIGHT INTO WEDNESDAY MORNING. MOISTURE AXIS WILL SHIFT EAST
TOWARD NORTHWEST ZONES LATE TONIGHT. CAPE VALUES WILL INCREASE UP
TO 3KJ/KG LATE TONIGHT THROUGH WEDNESDAY MORNING FIELD WITH
VEERING WINDS FROM SURF TO 600MB BUT NOT GREAT WIND SPEEDS. WITH
THE LITTLE WAVE FORECASTED TO PULL NORTHEAST OVER ARKANSAS AND
MISSOURI WEDNESDAY MORNING...THE STRONGEST DYNAMICS WILL BE NORTH OF THE
AREA. WITH THIS PACKAGE...WE ARE THINKING SCATTERED CONVECTION...A
FEW STRONG STORMS WITH SMALL SUB SEVERE HAIL AND STRONG WINDS
WEDNESDAY MORNING FOR AREAS NORTH OF BTR.

OTHERWISE...SCATTERED CONVECTION ON WEDNESDAY AS THE FRONTAL
STRUGGLES TO APPROACH THE AREA. MOISTURE WILL REMAIN IN PLACE FOR
THURSDAY...SO WILL MAINTAIN CHANCE POPS. THE MAIN TROUGH WILL
DEEPEN ON THE EAST COAST FLOW PUSHING THE BULK OF THE DRY AIR JUST
EAST OF FORECAST...TRICKY TEMPERATURE FORECAST WITH FRONTAL
PASSAGE ACROSS EAST ZONES FRIDAY NIGHT AND RELATIVELY DEEPER MOISTURE
OVER WEST ZONES. ERGO...WILL MAINTAIN A SLIGHT CHANCE ACROSS BTR
AND SOME RIVER PARISHES ON FRIDAY. MAIN TROUGH WILL LIFT OFF THE
EAST COAST AND LEAVING RIDGE TO SLOWLY AMPLIFY OVER SOUTHERN TIER
OVER THE WEEKEND AT 5H...COOL AIR WILL SLIP UNDERNEATH THIS
FEATURE AND CREATE MORE STABLE ATM THROUGH THE WEEKEND.

&&

.AVIATION...

MOST AREAS WILL SEE A CLOUD DECK DEVELOPING IN THE FL010-FL020
RANGE BETWEEN 04 AND 06Z. COULD SEE BRIEF MVFR WITH PATCHY FOG
BETWEEN 08 AND 12Z WEDNESDAY MORNING. WITH WINDS WILL DECREASE
THIS EVENING TO 3 TO 7 KNOTS AT ALL TERMINALS WEDNESDAY MORNING.
CONDITIONS SHOULD IMPROVE AROUND 15Z WITH CEILINGS ALL ABOVE
FL020. CONVECTIVE DEVELOPMENT MAY BTR AND MCB AS EARLY AS 10Z
WEDNESDAY MORNING AND THE OTHER SITES BETWEEN 12 AND 18Z. 18

&&

.MARINE...

RIDGE OF HIGH PRESSURE CENTERED IN THE WESTERN ATLANTIC EXTENDS INTO
THE NORTHEAST GULF OF MEXICO. IT WILL SLOWLY RETREAT EAST THROUGH
WEDNESDAY. THIS WILL KEEP WINDS SOUTHEASTERLY AT 10 TO 15
KNOTS...POSSIBLY A TOUCH ABOVE 15 KNOTS BRIEFLY IN SPOTS. SEAS THRU
THAT PERIOD TO BE MAINLY IN THE 2 FOOT RANGE...WITH THE EXCEPTION OF
THE WESTERN WATERS WITH 3 TO 4 FOOT WAVES POSSIBLE TODAY WITH
PERSISTENT WINDS NEAR 15 KNOTS.

UPPER LEVEL TROUGH WILL DIG ACROSS THE EASTERN HALF BEGINNING MID
WEEK. THIS WILL BREAK DOWN RIDGE OVER THE GULF COAST AND CAUSE THE
WIND FIELD TO BREAKDOWN. A WEAK FRONTAL BOUNDARY WILL PASS THROUGH
EASTERN LEGS OF MARINE ZONES FRIDAY NIGHT WITH A WIND SHIFT TO
THE NORTH THROUGH THE FIRST HALF OF THE WEEKEND. 18

&&

.DECISION SUPPORT...
DSS CODE...BLUE.
DEPLOYED...NONE.
ACTIVATION...NONE.
ACTIVITIES...SLURRY SUPPORT.
             MONITORING RIVER FLOODING.

DECISION SUPPORT SERVICES (DSS) CODE LEGEND
GREEN  = NO WEATHER IMPACTS THAT REQUIRE ACTION
BLUE   = LONG FUSED WATCH/WARNING/ADVISORY IN EFFECT OR HIGH
         VISIBILITY EVENT
YELLOW = HEIGHTENED IMPACTS WITH SHORT FUSED
         WATCH/WARNING/ADVISORY ISSUANCES; RADAR SUPPORT
ORANGE = HIGH IMPACTS - SLIGHT TO MODERATE RISK SEVERE; NEARBY
         TROPICAL EVENTS; HAZMAT OR OTHER LARGE EPISODES
RED    = FULL ENGAGEMENT FOR MODERATE TO HIGH RISK SVR
         AND/OR DIRECT TROPICAL THREATS; EVENTS OF NATIONAL
         SIGNIFICANCE

&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  69  87  68  90 /  20  50  20  30
BTR  74  89  70  90 /  20  50  20  30
ASD  73  88  69  89 /  10  30  20  30
MSY  75  87  72  87 /  10  30  20  30
GPT  74  86  68  86 /  10  30  20  30
PQL  68  86  67  88 /  10  30  20  30

&&

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

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE NEW ORLEANS LA
313 AM CDT WED MAY 22 2013

GMZ530-532-534-536-538-550-552-555-557-570-572-575-577-LAZ034>037-
039-040-046>050-056>072-MSZ068>071-077-080>082-222015-
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-
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-NORTHERN TANGIPAHOA-
SOUTHERN TANGIPAHOA-WILKINSON-AMITE-PIKE-WALTHALL-PEARL RIVER-
HANCOCK-HARRISON-JACKSON-
313 AM CDT WED MAY 22 2013

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

.DAY ONE...TODAY AND TONIGHT

SHOWERS AND THUNDERSTORMS WILL CONTINUE ACROSS SOUTHWEST
MISSISSIPPI AND PORTIONS OF SOUTHEAST LOUISIANA EARLY THIS
MORNING...MAINLY TO THE NORTH OF INTERSTATE 12. FREQUENT
LIGHTNING...WIND GUSTS TO 40 MPH AND VERY HEAVY RAIN ARE POSSIBLE
WITH THE STRONGER STORMS. AREAS THAT SEE REPEATED THUNDERSTORMS
COULD SEE AS MUCH AS THREE INCHES OF RAIN IN A COUPLE OF
HOURS...WHICH COULD PRODUCE TEMPORARY STREET FLOODING.

CONVECTION IS EXPECTED TO WEAKEN OR DISSIPATE THIS MORNING...BUT
MAY REDEVELOP BY MID-AFTERNOON. A FEW STRONG TO SEVERE
THUNDERSTORMS ARE POSSIBLE...WITH GUSTY TO DAMAGING WINDS BEING
THE MAIN THREATS.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY

ISOLATED THUNDERSTORMS ARE EXPECTED THURSDAY. WIDESPREAD SEVERE
WEATHER IS NOT EXPECTED. HOWEVER...ONE OR TWO STRONG STORMS WILL
BE POSSIBLE. THE MAIN THREATS WILL BE FREQUENT LIGHTNING AND GUSTY
WINDS.

FOR THE PERIOD FRIDAY THROUGH TUESDAY...NO HAZARDOUS WEATHER IS
EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT ANTICIPATED AT THIS TIME.

LAZ035-036-MSZ068-069-220830-

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE NEW ORLEANS LA
224 AM CDT WED MAY 22 2013

...CLUSTER OF STRONG THUNDERSTORMS MOVING EAST AFFECTING AMITE
COUNTY...WILKINSON COUNTY...EAST FELICIANA PARISH...WEST FELICIANA
PARISH...

AT 219 AM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
CLUSTER OF STRONG THUNDERSTORMS ALONG A LINE EXTENDING FROM 21 MILES
NORTHWEST OF LIBERTY TO 11 MILES NORTH OF ST. FRANCISVILLE...MOVING
EAST AT 20 MPH.

THE CLUSTER OF STRONG THUNDERSTORMS WILL AFFECT AREAS IN AND
AROUND...CROSBY...SPILLMAN...GLOSTER...CENTREVILLE...NORWOOD...
LIBERTY...FELPS AND SMITHDALE

THE PRIMARY THREATS FROM THESE STORMS ARE FREQUENT LIGHTNING AND WIND
GUSTS 35 TO 45 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.

THESE STORMS COULD PRODUCE RAINFALL AMOUNTS OF ONE TO TWO INCHES 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.

MSZ069>071-220915-

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE NEW ORLEANS LA
317 AM CDT WED MAY 22 2013

...CLUSTER OF STRONG THUNDERSTORMS MOVING EAST AFFECTING AMITE
COUNTY...WALTHALL COUNTY...PIKE COUNTY...

AT 312 AM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
CLUSTER OF STRONG THUNDERSTORMS ALONG A LINE EXTENDING FROM 9 MILES
NORTH OF LIBERTY TO LIBERTY TO 9 MILES NORTHEAST OF CLINTON...MOVING
EAST AT 30 MPH.

THE CLUSTER OF STRONG THUNDERSTORMS WILL AFFECT AREAS IN AND
AROUND...SMITHDALE...GILLSBERG...SUMMIT...MCCOMB...MCCOMB AIRPORT...
MAGNOLIA...TYLERTOWN AND SALEM

THE PRIMARY THREATS FROM THESE STORMS ARE FREQUENT LIGHTNING AND WIND
GUSTS 35 TO 45 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.

THESE STORMS COULD PRODUCE RAINFALL AMOUNTS OF ONE TO TWO INCHES 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.

LAZ035>037-220930-

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE NEW ORLEANS LA
329 AM CDT WED MAY 22 2013

...CLUSTER OF STRONG THUNDERSTORMS MOVING EAST AFFECTING ST. HELENA
PARISH...EAST FELICIANA PARISH...WEST FELICIANA PARISH...

AT 326 AM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
CLUSTER OF STRONG THUNDERSTORMS ALONG A LINE EXTENDING FROM 9 MILES
NORTH OF JACKSON TO 7 MILES WEST OF ZACHARY...MOVING EAST AT 30 MPH.

THE CLUSTER OF STRONG THUNDERSTORMS WILL AFFECT AREAS IN AND
AROUND...JACKSON...SLAUGHTER...NORWOOD...CLINTON...FELPS...DARLINGTON
AND EASLEYVILLE

THE PRIMARY THREATS FROM THESE STORMS ARE FREQUENT LIGHTNING AND WIND
GUSTS 35 TO 45 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.

THESE STORMS COULD PRODUCE RAINFALL AMOUNTS OF ONE TO TWO INCHES 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.