Severe Thunderstorm Warning 247, NWS Shreveport, LA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SHREVEPORT LA
1058 AM CDT SUN OCT 24 2010

.DISCUSSION...
ISOLATED CONVECTION IS STILL ONGOING ACROSS THE ERN SECTIONS OF
NCNTRL LA THIS MORNING...ALONG AN 850MB THETA-E RIDGE ORIENTED SW
TO NE FROM THE TOLEDO BEND COUNTRY INTO NCNTRL LA/SE AR...AND
ALONG THE TAIL END OF A WEAKENING SHORTWAVE THAT BROUGHT ABOUT THE
SCATTERED REPORTS OF SVR WEATHER SATURDAY ACROSS E TX. WE NOW
AWAIT THE NEXT AMPLIFYING SHORTWAVE EVIDENT ON THE WATER VAPOR
LOOP NOW ENTERING W TX...WHICH WILL AID IN THE DEVELOPMENT OF
ADDITIONAL CONVECTION LATER TODAY/THIS EVENING. THE 15Z SFC
ANALYSIS INDICATES A N-S WEAK CONFLUENT AXIS EXTENDING FROM SW AR
TO ALONG THE TX/LA LINE...EVIDENT IN THE STREAMLINE ANALYSIS.
MEANWHILE...A BROAD TONGUE TO 65+ DEGREE DEWPOINTS HAS SURGED N
INTO SE OK/CNTRL AR/MUCH OF THE ERN HALF OF TX...ALL OF LA AND
MUCH OF MS THIS MORNING...WITH EVEN 70+ DEWPOINTS ALSO ADVECTING N
ACROSS E TX/SRN LA. THIS HAS ALLOWED THE BEST SFC BASED
INSTABILITY TO SET UP W OF THE CONFLUENT ZONE OVER E TX THIS
MORNING...BUT THE PERSISTENT SSW LOW LEVEL FLOW TODAY WILL ALLOW
FOR ENHANCED INSTABILITY/POTENTIAL WEAK LOW LEVEL CONVERGENCE TO
SET UP FARTHER E ACROSS SW AR/N LA/E TX AS THE SHORTWAVE TO THE W
APPROACHES. THE 12Z NAM IS INDICATING A 1-2 PUNCH OF CONVECTION
ACROSS THE REGION THIS AFTERNOON...WITH SCT CONVECTION FIRING NEAR
THE GREATEST INSTABILITY AXIS /SBCAPES 1500-2000+ J/KG/ ACROSS E
TX/NW LA/SW AR BY MIDDAY/EARLY AFTERNOON AS DIFFLUENT FLOW BEGINS
TO OVERSPREAD THE REGION. WHILE SCT SVR CONVECTION CAN/T BE RULED
OUT HERE...BELIEVE THE MAIN FOCUS/THREAT FOR SVR WILL COME BY LATE
AFTERNOON/EVENING ACROSS MUCH OF THE REGION...AS THE PARENT
SHORTWAVE TROUGH SWINGS THROUGH.

VERY STEEP LAPSE RATES ALREADY LIE AHEAD OF THE TROUGH ACROSS
NCNTRL TX /PER THE 12Z KFWD RAOB/...WITH A DEEP LYR OF NEARLY DRY
ADIABATIC LAPSE RATES FROM 900-690MB. COUPLED WITH THE UNSTABLE
AIR MASS AT THE SFC...ANY RESIDUAL CONVECTIVE BNDRYS...AND 0-3 KM
HELICITIES BETWEEN 200-300 M2/S2 ADDING TO AN ALREADY BUOYANT AIR
MASS IN PLACE...SCT STRONG TO SVR CONVECTION WILL POSE A THREAT
ACROSS MUCH OF THE REGION EVEN AS THE BNDRY LYR GRADUALLY
STABILIZES WITH THE LOSS OF HEATING THIS EVENING. LARGE
HAIL/DAMAGING WINDS/ISOLATED TORNADOES WILL ALL BE POSSIBLE...WITH
THE ISOLATED TORNADO THREAT DIMINISHING TONIGHT AS DEEP LYR WINDS
BECOME MORE UNIDIRECTIONAL.

HAVE TONED DOWN POPS A TAD FOR E TX/SE OK/PORTIONS OF SW AR THIS
AFTERNOON...AS BEST FORCING WILL BE LATER/AWAY FROM THESE AREAS
THROUGH MUCH OF THE AFTERNOON HRS. MADE ONLY MINOR UPWARD ADJUSTMENTS
TO THE FORECAST MAX TEMPS...BUT CURRENT FORECAST REMAINS IN GOOD
SHAPE.

ZONE UPDATE ALREADY OUT...GRIDS WILL EB AVAILABLE SHORTLY.

&&

.AVIATION...
ALL IS QUIET AS OF 15Z AT LEAST AS FAR AS PRECIPITATION IS
CONCERNED. STILL DEALING WITH IFR/MVFR CEILINGS ACROSS MOST
TERMINALS BUT THIS SHOULD CONTINUE LIFTING OVER THE NEXT COUPLE OF
HOURS. ONCE THAT OCCURS AND WE GET SUFFICIENT MIXING...AS WAS THE
CASE ON SATURDAY...EXPECT SOUTHWEST WINDS TO INCREASE AS WE CONTINUE
TO HAVE A RATHER STRONG SURFACE PRESSURE GRADIENT IN PLACE. SOUTH TO
SOUTHWEST WINDS SUSTAINED AT 10 TO 14KTS WITH GUSTS APPROACHING
20KTS WILL BE COMMON ACROSS MOST AREAS...ESPECIALLY THE NE TX
TERMINALS. A STRONG UPPER LEVEL TROUGH WILL EJECT OUT OF NORTH
CENTRAL TEXAS LATE THIS AFTERNOON AND THUS...WE ARE EXPECTING AT
LEAST SCATTERED SHOWERS AND THUNDERSTORMS TO EFFECT THE TERMINALS
BEGINNING AROUND 19Z AND CONTINUING THROUGH THE LATE AFTERNOON AND
EVENING HOURS. EXPECT LOWERING OF CEILINGS AND VISIBILITIES IN AND
OUT OF CONVECTION THROUGH THIS EVENING ALONG WITH STRONG WIND GUSTS
SIMILAR TO THE CONVECTION THE NE TX TERMINALS EXPERIENCED SATURDAY
EVENING. LATE TONIGHT INTO THE MORNING HOURS ON MONDAY...EXPECT IFR
CEILINGS TO RETURN AREAWIDE AS LOW LEVEL MOISTURE WILL LIKELY BE
TRAPPED UNDER A STRONG INVERSION JUST OFF THE SURFACE. /13/

&&

.PRELIMINARY POINT TEMPS/POPS...
SHV  85  66  87  70  83 /  50  50  20  10  20
MLU  86  65  88  71  85 /  40  50  20  10  20
DEQ  81  58  83  61  79 /  30  60  20  20  20
TXK  82  64  85  66  80 /  40  60  20  20  20
ELD  84  63  85  69  82 /  50  60  20  10  20
TYR  83  66  87  68  80 /  40  50  20  10  20
GGG  84  66  88  68  81 /  40  50  20  10  20
LFK  87  67  89  72  85 /  30  40  20  10  20

&&

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

15/13

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE SHREVEPORT LA
1135 AM CDT SUN OCT 24 2010

ARZ050-051-059>061-070>073-LAZ001>006-010>014-017>022-OKZ077-
TXZ096-097-108>112-124>126-136>138-149>153-165>167-251100-
SEVIER-HOWARD-LITTLE RIVER-HEMPSTEAD-NEVADA-MILLER-LAFAYETTE-
COLUMBIA-UNION AR-CADDO-BOSSIER-WEBSTER-CLAIBORNE-LINCOLN-
UNION LA-DE SOTO-RED RIVER-BIENVILLE-JACKSON-OUACHITA-SABINE LA-
NATCHITOCHES-WINN-GRANT-CALDWELL-LA SALLE-MCCURTAIN-BOWIE-
FRANKLIN-TITUS-CAMP-MORRIS-CASS-WOOD-UPSHUR-MARION-SMITH-GREGG-
HARRISON-CHEROKEE-RUSK-PANOLA-NACOGDOCHES-SHELBY-ANGELINA-
SAN AUGUSTINE-SABINE TX-
1135 AM CDT SUN OCT 24 2010

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

.DAY ONE...THIS AFTERNOON AND TONIGHT...
SCATTERED SHOWERS AND THUNDERSTORMS WILL DEVELOP THIS AFTERNOON
ACROSS EAST TEXAS...NORTH LOUISIANA...AND SOUTHWEST ARKANSAS...AS
DEEP LAYER FORCING INCREASES AHEAD OF A STRONG UPPER LEVEL STORM
SYSTEM THAT WILL TRANSLATE EAST ACROSS TEXAS. AS ADDITIONAL
HEATING AND INCREASING LOW LEVEL MOISTURE RETURN CONTINUE ACROSS
THE REGION...THE AIR MASS WILL BECOME MODERATELY UNSTABLE...WITH
SOME OF THESE STORMS POSSIBLY BECOMING SEVERE. HOWEVER...THE MAIN
SEVERE WEATHER THREAT WILL WAIT UNTIL LATE AFTERNOON THROUGH THE
EVENING HOURS...AS THE UPPER LEVEL STORM SYSTEM ENTERS EASTCENTRAL
TEXAS. THESE STORMS WILL INITIATE ALONG THE DRY LINE NEAR OR JUST
EAST OF THE INTERSTATE 35 CORRIDOR OF CENTRAL TEXAS BY LATE
AFTERNOON...AND DEVELOP FARTHER EAST ACROSS MUCH OF THE REGION.
LARGE HAIL...DAMAGING WINDS...AND ISOLATED TORNADOES WILL BE THE
PRIMARY SEVERE WEATHER HAZARDS...WITH THE SEVERE WEATHER THREAT
GRADUALLY DIMINISHING FROM WEST TO EAST OVERNIGHT AS THE STORM
SYSTEM SHIFTS EAST ACROSS THE REGION.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY...
ISOLATED TO WIDELY SCATTERED SHOWERS AND THUNDERSTORMS WILL BE
POSSIBLE ACROSS THE FOUR STATE REGION TUESDAY...AHEAD OF A WEAK
COOL FRONT AND ASSOCIATED UPPER LEVEL DISTURBANCE THAT WILL MOVE
THROUGH THE REGION. ISOLATED THUNDERSTORMS WILL REMAIN POSSIBLE
WEDNESDAY AND THURSDAY ACROSS MAINLY EAST TEXAS AND NORTH
LOUISIANA NEAR THE FRONT AS IT BECOMES STATIONARY...BEFORE A
SECOND SURGE OF COOLER AND DRIER AIR FILTERS SOUTH INTO THE REGION
THURSDAY. THE PROBABILITY OF WIDESPREAD HAZARDOUS WEATHER IS LOW
TUESDAY AND WEDNESDAY.

.SPOTTER INFORMATION STATEMENT...
ACTIVATION OF EMERGENCY MANAGERS...SKYWARN NETWORKS...AND HAM
RADIO OPERATORS...WILL LIKELY BE NEEDED THIS AFTERNOON AND
EVENING.

15

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