National Weather Service Weather Forecast Office

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXUS64 KSHV 200954
AFDSHV

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SHREVEPORT LA
454 AM CDT MON MAY 20 2013

.DISCUSSION...
A 40KT SSW LLJ EVIDENT IN THE KSHV 88-D VAD HAS ADVECTED EXTENSIVE
AREAS OF STRATUS N INTO THE AREA THIS MORNING...AND HAS ALSO NOT
ALLOWED TEMPS TO FALL MUCH OVERNIGHT...ESPECIALLY OVER NCNTRL LA WHERE
09Z TEMPS REMAIN IN THE MID/UPPER 70S. SHOULD SEE ANOTHER HOT AND
HUMID DAY AS THIS CLOUD SHIELD LIFTS/SCATTERS OUT BY LATE
MORNING...EVEN AS THE PRESSURE GRADIENT TIGHTENS OVER THE SRN PLAINS
AS SFC LOW PRESSURE ALONG THE DRYLINE ALONG THE ERN TX PANHANDLE/WRN OK
BORDER SINKS S INTO NW TX AND DEEPENS WITH HEATING. WINDS WERE
MARGINAL FOR THE LAKE WIND ADVISORY SUNDAY...AND THIS SHOULD AGAIN BE
THE CASE TODAY...THUS WILL ALLOW THE CURRENT LAKE WIND ADVISORY TO
REMAIN IN PLACE FOR E TX/SE OK/EXTREME SW AR/WRN LA. LOW LEVEL THERMAL
PROFILES INDICATE THAT MAX TEMPS TODAY COULD BE A TAD WARMER THAN WHAT
WAS OBSERVED SUNDAY...AND GIVEN THE VERY MILD START TO THIS
MORNING...SEE NO REASON TO ARGUE AND THUS HAVE BUMPED MAX TEMPS UP A
COUPLE DEGREES FROM THE PREVIOUS FORECAST.

THE MORNING WATER VAPOR IMAGERY INDICATES OUR CLOSED LOW CENTERED OVER
SD/NE...WITH THIS LOW EXPECTED TO WOBBLE OVER THE NEXT 24 HOURS WITH
THE NEXT SHORTWAVE/SPEED MAX ROTATING ENE ACROSS OK THIS
AFTERNOON/EVENING. THIS SHOULD AGAIN IGNITE VIGOROUS CONVECTION
ALONG THE DRYLINE ACROSS CNTRL OK/WCNTRL LA BY MID/LATE
AFTERNOON...WITH THE OK CONVECTION ORGANIZING INTO A MCS LATER THIS
EVENING AS IT PROPAGATES ENE INTO ERN OK. CAN/T ARGUE WITH THE
SPC MODERATE RISK JUST NW OF THE FORECAST AREA LATE THIS
AFTERNOON/TONIGHT...WITH THE SRN EDGE OF THIS CONVECTION PROGGED TO
EXPAND MORE SE INTO SE OK/ADJACENT SW AR AFTER 06Z ALONG A 40-50KT
SWRLY LLJ. DESPITE THE LATE ARRIVAL OF THIS CONVECTION INTO OUR NW
ZONES TONIGHT...MODERATE SFC BASED CAPES OF 1000-1500 J/KG SHOULD
PERSIST NW OF THE I-30 CORRIDOR WITHIN A CORRIDOR OF STEEP MID LEVEL
LAPSE RATES. THUS...HAVE ADDED SVR MENTION TO THE EXTREME NW ZONES
LATE AS THIS CONVECTION COULD REMAIN STRONG/POSSIBLY SVR THROUGH EARLY
TUESDAY MORNING.

THERE/S NO DOUBT THAT MESOSCALE BNDRYS FROM THIS CONVECTION WILL BE
KEY TO INITIATION OF CONVECTION TUESDAY...ESPECIALLY AS THE PRIMARY
TROUGH EXTENDING FROM NRN UT/ERN NV THIS MORNING SWINGS E INTO THE
SRN PLAINS TUESDAY MORNING. THUS...PERSISTENT DIFFLUENCE ALOFT SHOULD
MAINTAIN SCT CONVECTION MAINLY ALONG/NW OF THE I-30 CORRIDOR THROUGH
MUCH OF THE DAY. BELIEVE THAT CLOUD COVER AND RAIN WILL LIMIT HEATING
OVER THESE AREAS...ALTHOUGH DIFFERENTIAL HEATING BNDRYS MAY COME INTO
PLAY ESPECIALLY AS LARGE SCALE FORCING INCREASES TUESDAY AFTERNOON
DURING PEAK HEATING ONCE THE TROUGH APPROACHES FROM THE W. DEEP LAYER
SHEAR OF 40-50KTS WILL PERSIST THROUGH MUCH OF THE DAY FROM NE TX INTO
SE OK/SW AR...WITH THE NAM/GFS CONSISTENT IN GENERATING 2500-3000 J/KG
OF MLCAPE ACROSS THESE AREAS. STEEP MID LEVEL LAPSE RATES AHEAD OF THE
TROUGH WILL ONLY ENHANCE THE DEVELOPMENT OF CLUSTERS OF STRONG/SVR
CONVECTION TUESDAY AFTERNOON FROM NE TX/SE OK/SW AR...WHICH SHOULD
PROPAGATE ESE INTO EXTREME NRN LA BY LATE AFTERNOON/EARLY EVENING. DID
MAINTAIN LIKELY/HIGH CHANCE POPS FOR THESE AREAS WHILE ALSO ADDING SVR
WORDING TO THE FORECAST...BUT RAISED POPS TUESDAY NIGHT TO LIKELY OVER
MUCH OF THE AREA AS A MCS DEVELOPS AND PROGRESSES ACROSS THE REGION.
GIVEN THE STRONG FORCING ALOFT AND HIGH PW/S...LOCALLY HEAVY RAINFALL
WILL BE POSSIBLE ESPECIALLY FROM E TX INTO NW LA/SW AR...WHERE QPF
TOTALS OF 1-3+ INCHES WILL BE LIKELY.

THIS CONVECTION SHOULD GRADUALLY WEAKEN AS IT EXITS THE REGION WEDNESDAY
MORNING WITH THE DEPARTURE OF THE TROUGH. DID MAINTAIN CHANCE POPS
FROM DEEP E TX INTO N LA/SCNTRL AR WEDNESDAY MORNING...BEFORE
GRADUALLY TAPERING POPS FROM W TO E DURING THE AFTERNOON. A NW FLOW
ALOFT WILL SET UP FROM THE PLAINS INTO THE LOWER MS VALLEY LATE
WEDNESDAY...ONCE UPPER RIDGING IS ESTABLISHED ACROSS THE WRN PLAINS
AHEAD OF A CLOSED LOW OVER THE PACIFIC NW...AND TROUGHING FROM THE
GREAT LAKES INTO THE OH/TN VALLIES. DID MAINTAIN SLIGHT CHANCE POPS
THURSDAY OVER THE NE HALF OF THE REGION AS WEAK VORTICITY
PERTURBATIONS MIGRATE SE FROM OK INTO WRN/CNTRL AR. TROUGHING ALOFT E
OF THE MS VALLEY WILL ALLOW FOR A WEAK COOL FRONT TO BACKDOOR SW INTO
SE OK/SRN AR/N LA FRIDAY...WITH THE VORTICITY AXIS EXPANDING A LITTLE
FARTHER W. THUS...THE WWD EXPANSION OF SLIGHT CHANCE POPS LOOKS GOOD
FRIDAY...WITH SLIGHTLY COOLER AND DRIER AIR BACKDOORING INTO MUCH OF
THE REGION THIS WEEKEND AS THE BNDRY STALLS. SHOULD START TO SEE TEMPS
WARM BACK TO NEAR 90 LATE THIS WEEKEND AND INTO MEMORIAL DAY WITH THE
BNDRY WASHING OUT AND A MORE SRLY LOW LEVEL FLOW RETURNING.

PRELIMS TO FOLLOW BELOW...

15

&&

.AVIATION...
PATCHY MVFR CIGS STREAMING NORTHWARD THIS AM...WILL BECOME MORE
WIDESPREAD BY AROUND 20/10Z...AND MAY GRADUALLY LOWER TO LOW MVFR.
SOUTH WINDS 10 TO 15 KTS OVER NE TX...AND AROUND 10 KTS ELSEWHERE.
THESE WINDS TO INCREASE TO 15 TO 20 KTS AND GUSTY THIS AFTN...AND
NOT SIGNIFICANTLY DIMINISH AFTER 21/0Z AS PRESSURE GRADIENT TIGHTENS
IN RESPONSE TO SLOWLY APPROACHING COLD FFONT MOVG INTO SOUTHERN
PLAINS. CAP WILL WEAKEN AREAWIDE ON TUE AFTN. MORNING CIGS BECMG SCT
VFR BY AROUND 20/15Z TODAY AND MVFR CIGS RETURNING ONCE AGAIN TO
AREA AFTER 21/06Z. A FEW STORMS POSSIBLE NEAR THE KTXK TERMINAL AS
EARLY AS 21/12Z. /07/

&&

.PRELIMINARY POINT TEMPS/POPS...
SHV  91  73  88  68  86 /   5  10  50  70  30
MLU  91  72  89  69  85 /   5   5  30  60  50
DEQ  89  69  81  63  86 /  10  50  60  70  10
TXK  89  71  84  66  86 /  10  30  60  70  20
ELD  90  71  86  67  86 /   5  10  50  70  30
TYR  91  72  86  68  86 /   5  20  50  70  20
GGG  91  72  87  68  86 /   5  20  50  70  20
LFK  92  72  90  71  89 /   5  10  20  60  30

&&

.SHV WATCHES/WARNINGS/ADVISORIES...
AR...LAKE WIND ADVISORY FROM 10 AM THIS MORNING TO 7 PM CDT THIS
     EVENING FOR THE FOLLOWING ZONES: ARZ050-051-059-060-070-071.

LA...LAKE WIND ADVISORY FROM 10 AM THIS MORNING TO 7 PM CDT THIS
     EVENING FOR THE FOLLOWING ZONES: LAZ001-002-010-011-017.

OK...LAKE WIND ADVISORY FROM 10 AM THIS MORNING TO 7 PM CDT THIS
     EVENING FOR THE FOLLOWING ZONES: OKZ077.

TX...LAKE WIND ADVISORY FROM 10 AM THIS MORNING TO 7 PM CDT THIS
     EVENING FOR THE FOLLOWING ZONES:
     TXZ096-097-108>112-124>126-136>138-149>153-165>167.

&&

$$

15/07