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000
FXUS64 KSHV 221500
AFDSHV

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SHREVEPORT LA
1000 AM CDT WED MAY 22 2013

.DISCUSSION...
CURRENT FORECAST IS ON TRACK THIS MORNING. LOW CLOUDS FORECAST
TO BURN OFF LATER THIS MORNING AS DRIER AIR MIXES DOWN TO THE SURFACE
IN CONJUNCTION WITH DIURNAL HEATING. DESPITE MORNING CLOUD
COVER...HIGH TEMPERATURES STILL ON TRACK TO CLIMB INTO THE MID TO
UPPER 80S THIS AFTERNOON AS SUBSIDENCE INCREASES AHEAD OF AN UPPER
RIDGE BUILDING EAST FROM THE ROCKIES. /05/

&&

.AVIATION...
LOW CLOUDS ARE SLOWING ERODING BUT SOME TERMINALS MAY STILL BE
EXPERIENCING MVFR CIGS AT THE START OF THE 12Z TAF PERIOD. CONTINUED
IMPROVEMENT IS EXPECTED AS DRIER AIR FILTERS INTO THE REGION BEHIND
A DEPARTING COLD FRONT AND VFR CONDITIONS ARE EXPECTED AREAWIDE FOR
MOST OF THE REMAINDER OF THE PERIOD. LIGHT WINDS...CLEAR SKIES...AND
WET SOILS WILL LIKELY LEAD TO SOME PATCHY FOG AROUND SUNRISE
THURSDAY MORNING. ANY FOG THAT DEVELOPS SOME DISSIPATE BEFORE
23/18Z. /09/

&&

.PREV DISCUSSION... /ISSUED 442 AM CDT WED MAY 22 2013/

DISCUSSION...
THE NEGATIVE TILT UPPER TROUGH CONTINUES TO MAKE STEADY PROGRESS E
ACROSS CNTRL OK/TX THIS MORNING...WITH THE WATER VAPOR IMAGERY
INDICATING DRIER AIR ALOFT ENTRAINING INTO THE CONVECTION OVER SE
TX/SCNTRL LA. THIS WILL RESULT IN DIMINISHING RAINFALL TRENDS OVER THE
SE SECTIONS OF NCNTRL LA THROUGH 12Z...ALTHOUGH THE KSHV 88-D LOOPS
AND SFC OBS REFLECT VERY WEAK ECHOS IN A NE TO SW BAND FROM SW AR INTO
NE TX...INDICATIVE OF THE 850MB TROUGH POSITION WHICH HAS RESULTED IN
PATCHY -RA DEVELOPMENT ALONG THIS PARENT AXIS. WHILE THE CONVECTION
HAS PUSHED A RAIN COOLED OUTFLOW BNDRY S INTO SRN LA THIS MORNING...A
WEAK SFC FRONT THAT DOES NOT SHOW UP IN THE SFC PRESSURE ANALYSIS BUT
RATHER IN THE SFC THETA-E PLOT REMAINS NEARLY STATIONARY FROM WRN AR
INTO THE WRN SECTIONS OF E TX...NEAR OR JUST W OF THE 850MB TROUGH
POSITION. WILL MAINTAIN SLIGHT CHANCE POPS FOR MUCH OF THE AREA THIS
MORNING AHEAD OF THE 850MB TROUGH...WITH LOW CHANCE POPS OVER THE SRN
AND ERN SECTIONS OF NCNTRL LA WHERE THETA-E RIDGING MAY ENHANCE JUST
ENOUGH LIFT ALONG THE UPPER TROUGH AXIS FOR WIDELY SCT REDEVELOPMENT.
ALSO OF CONCERN IS THE EWD PROGRESSION OF THE BACK EDGE OF THE VERY
LOW STRATUS SHIELD OVER SE OK/ECNTRL TX...WHICH HAS ALLOWED FOR PATCHY
FG TO DEVELOP NEAR THIS BANK AND AREAS TO THE W WHERE THE SKY HAS
CLEARED. HAVE ADDED PATCHY FG WORDING THROUGH MIDMORNING TO THE
FORECAST ACROSS THE WRN SECTIONS OF E TX/SE OK/ADJACENT SW AR...WITH
THIS WEAK SFC FRONT EXPECTED TO DRIFT E TO NEAR THE MID-SOUTH REGION
SW INTO NCNTRL LA/DEEP E TX LATER THIS AFTERNOON BEFORE STALLING. DID
RETAIN SLIGHT CHANCE POPS FOR THE AFTERNOON ALONG AND AHEAD OF THIS
BNDRY...AS AFTERNOON HEATING MAY YIELD ENOUGH FORCING IN A MORE MOIST
ENVIRONMENT FOR ISOLATED CONVECTION TO DEVELOP.

WHAT/S LEFT OF THIS SFC FRONT MAY ACTUALLY DRIFT BACK N OVER E TX/N LA
OVERNIGHT ALLOWING FOR SCT CU TO REDEVELOP...BUT OTHERWISE...LIGHT
WINDS SHOULD ALLOW FOR MIN TEMPS TO FALL BACK TO NEAR NORMAL...WITH WHAT
WILL BE OBSERVED THIS MORNING. NW FLOW ALOFT WILL COMMENCE TODAY AHEAD
OF THE ERN SD CLOSED LOW AND ACCOMPANYING TROUGH AS IT DRIFTS SE INTO
THE MIDWEST. THE WRN PLAINS RIDGING SHOULD BEGIN TO AMPLIFY N TO THE
CANADIAN BORDER THURSDAY AS THE MIDWEST TROUGH PROGRESSES E THROUGH
THE OH/TN VALLIES...WITH A CLOSED LOW EXPECTED TO WOBBLE OVER THE PAC
NW. THE NAM REMAINS QUITE AGGRESSIVE IN DEVELOPING WIDELY SCT
CONVECTION ALONG A SFC TROUGH/WARM FRONT LATE TONIGHT ALONG THE MID
AND UPPER RED RIVER VALLEY OF NW TX/SW OK...WITH A SWRLY 20-30KT LLJ
MAINTAINING THIS CONVECTION AS IT TRACKS SE OVER SRN OK. WILL MAINTAIN
SLIGHT CHANCE POPS FOR SE OK/SW AR THURSDAY ALTHOUGH ANY CONVECTION
THAT MAY DEVELOP SHOULD WEAKEN BY LATE MORNING/EARLY AFTERNOON AS LOW
LEVEL CONVERGENCE WEAKENS FARTHER E ALONG THE RED RIVER VALLEY. SHOULD
SEE TEMPS WARM BACK TO NEAR 90 THURSDAY ALONG/S OF I-20 NEAR THE
RESIDUAL SFC FRONT...BEFORE A WEAK COOL FRONT BEGINS TO BACKDOOR SW
INTO THE REGION LATE THURSDAY NIGHT.

THIS BACKDOOR FRONT SHOULD TAPER TEMPS/DEWPOINTS A FEW DEGREES FRIDAY
THROUGH MUCH OF THE WEEKEND AS IT STALLS FROM CNTRL OK INTO ECNTRL TX.
IT/S INTERESTING TO NOTE THAT BOTH THE GFS AND ECMWF NOW DEVELOP A
WEAK VORTICITY PERTURBATION WITHIN THE NW FLOW OVER THE TX PANHANDLE
FRIDAY...LIKELY AS A RESULT OF ISOLATED STRONG CONVECTION THAT MAY
DEVELOP...WITH THIS VORTICITY AXIS DRIFTING SE ACROSS CNTRL OK/TX
FRIDAY NIGHT AND SATURDAY WITHIN THE RIDGING ALOFT. DID INSERT MENTION
OF SLIGHT CHANCE POPS FOR NE TX/SE OK/SW AR SATURDAY AS DAYTIME
HEATING AND A WEAK SSW RETURN FLOW OVER THESE AREAS MAY YIELD ISOLATED
CONVECTION. BY SUNDAY...THIS VORTICITY AXIS SHOULD HAVE BEEN SHUNTED
FAR ENOUGH E INTO THE DRIER POST-FRONTAL AIR MASS SUCH THAT THE
FORECAST SHOULD REMAIN DRY THROUGHOUT THE REMAINDER OF THE
EXTENDED...AS THE UPPER RIDGE PERSISTS OVER THE LOWER MS VALLEY.
SHOULD START TO SEE TEMPS WARM BACK TO NEAR 90 LATE IN THE WEEKEND
THROUGH MUCH OF NEXT WEEK AS THE RIDGE ALOFT IS ESTABLISHED OVER THE
AREA...AND SRLY LOW LEVEL WINDS ALLOW FOR A GRADUAL MODIFICATION OF
RH/S.

PRELIMS TO FOLLOW BELOW...

15

AVIATION...
SHRA/TSRA ACTIVITY DEPARTING TO THE EAST THIS MORNING...LEAVING
MVFR/IFR FLIGHT CONDITIONS AT MOST SITES. SOME FG POSSIBLE ACROSS E
TX TAF SITES THIS MORNING AS STRATUS IS CLEARING FROM WEST TO EAST
BEHIND THE FRONT. SHOULD SEE IMPROVEMENT TO MVFR THEN TO VFR BEFORE
NOON TODAY...WITH ONLY SOME HIGH CLOUDS EXPECTED AND LIGHTER
WINDS...PRIMARILY OUT OF THE NORTH/NORTHWEST BEFORE GOING LIGHT AND
VARIABLE LATE THIS EVENING. LIGHT WINDS...CLEAR SKIES AND WET GROUND
CONDITIONS MAY LEAD TO PATCHY FOG DEVELOPMENT BEFORE 23/12Z. /20/

&&

.PRELIMINARY POINT TEMPS/POPS...
SHV  86  64  91  68  85 /  20  10  10  10  20
MLU  87  63  90  65  83 /  30  10  10  10  20
DEQ  83  59  85  63  79 /   0   0  20  10  20
TXK  84  61  87  65  80 /  10   0  20  10  20
ELD  85  61  88  63  80 /  20   0  20  10  20
TYR  86  65  90  69  85 /   0  10  10  10  20
GGG  86  65  90  68  85 /  10  10  10  10  20
LFK  89  68  91  69  89 /  20  10  10  10  20

&&

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

$$

05/09/09