Severe Thunderstorm Warning 124, NWS Shreveport, LA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SHREVEPORT LA
427 PM CDT TUE MAY 21 2013

.DISCUSSION...

TORNADO WATCH CONTINUES IN EFFECT UNTIL 10 PM CDT. A VERY MOIST
AND UNSTABLE AIR MASS REMAINED OVER MUCH OF THE FOUR STATE REGION
THIS AFTERNOON WITH SCATTERED SHOWERS AND THUNDERSTORMS OVER
NORTHEAST TEXAS INTO SOUTHWEST ARKANSAS AND IN SOUTHEAST OKLAHOMA.
THESE THUNDERSTORMS WERE ALONG A SURFACE TROUGH OF LOW PRESSURE
EXTENDING EAST FROM SURFACE LOW PRESSURE OVER NORTH TEXAS. APPROACHING
TO THE WEST IS ANOTHER BAND OF SHOWERS AND THUNDERSTORMS OUT AHEAD
OF AN UPPER TROUGH OF LOW PRESSURE DROPPING SOUTHWEST ACROSS THE
CENTRAL AND SOUTHERN PLAINS AND INTO THE BIG BEND AREA OF WEST
TEXAS. THESE STORMS WERE ALONG A SURFACE BOUNDARY THAT WAS NEARLY
STATIONARY FROM NORTHEAST OKLAHOMA INTO NORTHWEST TEXAS AROUND THE
SURFACE LOW AND SOUTH ALONG THE COLD FRONT FROM NORTHWEST TEXAS
INTO THE DRY LINE INTERSECTION NORTH OF BIG BEND. AS THE UPPER
TROUGH OF LOW PRESSURE SWINGS EAST DURING THE LATE AFTERNOON AND
OVERNIGHT...ADDITIONAL SHOWERS AND THUNDERSTORMS WILL DEVELOP EAST
OVER THE FOUR STATE REGION. SOME OF THE THUNDERSTORMS WILL BE
STRONG TO SEVERE PRODUCING LARGE HAIL...HIGH AND DAMAGING WINDS...
DEADLY LIGHTNING...LOCALLY HEAVY RAINFALL...AND ISOLATED TORNADOES.
RAINFALL AMOUNTS WILL RANGE FROM NEAR ONE TO TWO INCHES WITH HIGHER
AMOUNTS AS STORMS TRAIN OVER SOME OF THE SAME LOCATIONS. BY EARLY
WEDNESDAY MORNING NEAR 7 AM CDT THE COLD FRONT WILL EXTEND FROM
NEAR A HOT SPRINGS ARKANSAS TO SHREVEPORT LOUISIANA AND LUFKIN
TEXAS LINE. THE UPPER TROUGH AXIS WILL BE DROPPING SOUTH INTO THE
FOUR STATE REGION WITH STORMS DECREASING FROM NORTHWEST TO
SOUTHEAST AS UPPER SUPPORT AND THE FRONTAL SYSTEM CONTINUE OFF TO
THE EAST. THE SURFACE BOUNDARY WILL BECOME NEARLY STATIONARY
KEEPING RAIN CHANCES IN FOR SOUTHERN SECTIONS. AN UPPER RIDGE AMPLIFIES
NORTH ACROSS TEXAS AND INTO THE CENTRAL AND NORTHERN SECTIONS OF
THE COUNTRY FOR LATE WEEK KEEPING A NORTHWEST FLOW PATTERN OVER
THE FOUR STATE REGION WITH THE UPPER TROUGH DROPPING SOUTH FROM
THE GREAT LAKES SOUTH INTO THE SOUTHEAST STATES. WILL KEEP LOW END
POPS IN UNDER THE INFLUENCE OF THE UPPER RIDGE FOR THE LATE PART OF
THE EXTENDED. /06/

&&

.AVIATION...

FIRST ROUND OF CONVECTION IS RAPIDLY DEVELOPING ALONG THE I-30
CORRIDOR. ADDITIONAL DEVELOPMENT BACK TO THE WSW IS LIKELY THIS
AFTERNOON. THIS ACTIVITY IS EXPECTED EVENTUALLY TO CONGEAL INTO A
SINGLE COMPLEX AND WILL GENERALLY REMAIN NORTH OF I-20. A SECOND
CONVECTIVE COMPLEX HAS DEVELOPED ACROSS ERN OK SWD TOWARDS THE DFW
METROPLEX AHEAD OF A COLD FRONT. THE COMPLEX WILL EVENTUALLY AFFECT
MOST OF THE TAF SITES AND SHOULD BE CLOSE TO A KLFK-KASL-MAGNOLIA AR
LINE AROUND THE START OF THE 00Z TAF PERIOD. EXPECT DETERIORATING
FLIGHT CONDITIONS IN THE VICINITY OF ANY CONVECTION. MVFR OR LOWER
CONDITIONS WILL BE LIKELY. VERY HEAVY RAINFALL...DAMAGING
WINDS...LARGE HAIL...AND ISOLATED TORNADOES WILL BE POSSIBLE THROUGH
THE EVENING.

THE COLD FRONT MAY SLOW DOWN AND THE SECOND LINE OF CONVECTION MAY
BEGIN TO OUTRUN IT. THIS MAY ALLOW FOR SOME SCATTERED REDEVELOPMENT
ALONG THE FRONT THROUGH THE OVERNIGHT AND EARLY MORNING HOURS. COLD
FRONT SHOULD BEGIN TO ENTER THE WRN FRINGES OF THE AREA AFTER
22/06Z. WINDS SHOULD SHIFT TO THE NW AFTER THE FRONT PASSES. PRECIP
SHOULD SHOULD GRADUALLY END FROM NW TO SE DURING THE DAYTIME HOURS
OF WEDNESDAY. /09/

&&

.PRELIMINARY POINT TEMPS/POPS...
SHV  69  86  65  91  69 /  80  30  10  10  10
MLU  69  86  63  90  66 /  80  60  10  20  20
DEQ  58  83  57  88  62 /  80  10  10  20  20
TXK  65  86  60  88  65 /  80  10  10  10  10
ELD  65  84  59  89  63 /  80  30  10  20  20
TYR  65  87  65  89  70 /  80  10  10  10  10
GGG  65  86  65  90  69 /  80  20  10  10  10
LFK  69  89  68  91  69 /  80  30  10  10  10

&&

.SHV WATCHES/WARNINGS/ADVISORIES...
AR...NONE.
LA...NONE.
OK...NONE.
TX...NONE.
&&

06/09

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE SHREVEPORT LA
1245 PM CDT TUE MAY 21 2013

ARZ050-051-059>061-070>073-LAZ001>006-010>014-017>022-OKZ077-TXZ096-
097-108>112-124>126-136>138-149>153-165>167-221100-
ANGELINA-BIENVILLE-BOSSIER-BOWIE-CADDO-CALDWELL-CAMP-CASS-CHEROKEE-
CLAIBORNE-COLUMBIA-DE SOTO-FRANKLIN-GRANT-GREGG-HARRISON-HEMPSTEAD-
HOWARD-JACKSON-LA SALLE-LAFAYETTE-LINCOLN-LITTLE RIVER-MARION-
MCCURTAIN-MILLER-MORRIS-NACOGDOCHES-NATCHITOCHES-NEVADA-OUACHITA-
PANOLA-RED RIVER LA-RED RIVER TX-RUSK-SABINE LA-SABINE TX-
SAN AUGUSTINE-SEVIER-SHELBY-SMITH-TITUS-UNION AR-UNION LA-UPSHUR-
WEBSTER-WINN-WOOD-
1245 PM CDT TUE MAY 21 2013

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTH CENTRAL
AND SOUTHWEST ARKANSAS...NORTH CENTRAL AND NORTHWEST
LOUISIANA...SOUTHEAST OKLAHOMA...AND EAST AND NORTHEAST TEXAS.

.DAY ONE...THIS AFTERNOON AND TONIGHT...

THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS TODAY ACROSS MUCH
OF EAST TEXAS...SOUTHEAST OKLAHOMA...SOUTHWEST ARKANSAS...AND
NORTHWEST LOUISIANA AND PARTS OF NORTH CENTRAL LOUISIANA. AN UPPER
LEVEL TROUGH OF LOW PRESSURE WILL SHIFT EAST ACROSS THE SOUTHERN
PLAINS THIS AFTERNOON AND OVERNIGHT...AND INTERACT WITH STRONG
INSTABILITY...VARIOUS CONVECTIVE BOUNDARIES LEFT IN PLACE FROM
SHOWERS AND THUNDERSTORMS EARLIER MONDAY NIGHT AND EARLY TUESDAY
MORNING...AND A MOIST ATMOSPHERE. ONGOING SHOWERS AND
THUNDERSTORMS OVER SOUTHEAST OKLAHOMA INTO SOUTHWEST ARKANSAS
AND EXTREME NORTHEAST TEXAS WILL EXPAND AND DEVELOP OVER
REMAINING PARTS OF THE FOUR STATE REGION. WINDS FEEDING INTO THE
AREA WILL BE TURNING WITH HEIGHT PROVIDING WIND SHEAR WHICH WILL
HELP WITH UPDRAFT ROTATION...SUCH THAT SOME OF THESE STORMS WILL
BECOME SEVERE...CAPABLE OF PRODUCING DAMAGING WINDS...LARGE HAIL...
AND ISOLATED TORNADOES. THESE STORMS WILL ALSO PRODUCE LOCALLY HEAVY
RAINFALL AT TIMES...GIVEN THE AMOUNT OF MOISTURE PROVIDED BY
THE GULF OF MEXICO...THAT CAN PRODUCE FROM ONE TO THREE INCHES
OF RAIN ACROSS NORTHEAST TEXAS...SOUTHEAST OKLAHOMA...
SOUTHWEST ARKANSAS AND NORTHWEST LOUISIANA. THESE STORMS SHOULD
CONSOLIDATE INTO A LARGE THUNDERSTORM COMPLEX TONIGHT AS IT
PROPAGATES EAST SOUTHEAST ACROSS SOUTHWEST ARKANSAS AND NORTH
LOUISIANA...WHERE STRONG DAMAGING STRAIGHT LINE WINDS WILL BE
POSSIBLE. SHOWERS AND THUNDERSTORMS SHOULD WEAKEN LATE TONIGHT
AND EARLY WEDNESDAY MORNING NORTH CENTRAL LOUISIANA AS
INSTABILITY GRADUALLY DIMINISHES.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY...

SHOWERS AND THUNDERSTORMS SHOULD BE ONGOING WEDNESDAY MORNING
ACROSS NORTH CENTRAL LOUISIANA AND PORTIONS OF DEEP EAST
TEXAS...BUT SHOULD DIMINISH FROM WEST TO EAST BY LATE MORNING
WITH THE DEPARTURE OF THE UPPER TROUGH. ISOLATED SHOWERS AND
THUNDERSTORMS MAY REDEVELOP WEDNESDAY AFTERNOON MAINLY SOUTH OF
INTERSTATE 20 OVER EAST TEXAS AND NORTH LOUISIANA...WHERE A WEAK
SURFACE BOUNDARY BECOMES STATIONARY. THESE STORMS SHOULD
DIMINISH WEDNESDAY EVENING WITH THE LOSS OF HEATING.

.SPOTTER INFORMATION STATEMENT...

ACTIVATION OF EMERGENCY MANAGERS...SKYWARN NETWORKS...AND AMATEUR
RADIO PERSONNEL...WILL BE REQUIRED THIS AFTERNOON AND TONIGHT.

06

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