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000
FXUS64 KSHV 131700
AFDSHV

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SHREVEPORT LA
1100 AM CST FRI DEC 13 2013

.DISCUSSION...
DEW POINTS ARE RISING NOW OVER OUR WEST WITH DECENT COVERAGE OF RAIN
SHOWERS ALREADY THAT WILL BE PUSHING INTO SW AR AND NW LA PRIOR TO
18Z. SO HAVE MADE SOME CHANGES TO LIKELY POPS/WX FOR THE REMAINING
HOUR THERE AND SOME FOR 18-00Z AS WELL...READING REST OF TODAY.
ISOLATED ELEVATED THUNDERSTORMS ARE OVER E TX NOW AND MOVING NE AT
45 MPH. SPC HAS UPDATED THERE GENERAL OUTLOOK TO INCLUDE MOST OF
OUR AREA N OF I-20 AND 50 MILES OR SO SOUTH W TO E.

OUR TEMPERATURES ARE SATURATING WEST AND HAVE LOWERED IN QUITE A
FEW SPOTS FOR THE AFTERNOON HIGH SO TO SPEAK. THE WATER VAPOR
SHOWS A GOOD MID LEVEL DRY SLOT WORKING IN OVER OK/N TX...SO THIS
EVENT MAY BE SPEEDING UP A BIT WITH SOME OF THE HEAVIER ACTIVITY
LIKELY TO CLEAR OUT FASTER OVER THE WEST AND WILL ADDRESS THAT
WITH MORE MODEL DATA IN THE AFTERNOON PACKAGE WITH PERHAPS A PRE
PERIOD ISSUANCE. OTHERWISE...NO OTHER CHANGES NEEDED AT THIS TIME.

&&

.AVIATION...
CLOUDS CONTINUE TO INCREASE THIS MORNING OVER THE FOUR STATE REGION
AS AN APPROACHING UPPER TROF DRAWS CLOSER FROM THE WEST. A WIDE
RANGE OF CIGS ACROSS THE CWA WITH LOW END VFR AT TYR...LIKELY MVFR
BY THE START OF THE 18Z TAF PERIOD AND SHORTLY THEREAFTER AT GGG/LFK
AS WELL. FARTHER EAST AT THE AR/LA TERMINALS...MOSTLY MID AND HIGH
CLOUDS THIS MORNING BUT LOWER CIGS WILL GRADUALLY FILL IN FROM THE
WEST DURING THE AFTERNOON. RAIN SHWRS HAVE ALREADY BEEN OBSERVED FOR
MUCH OF THE MORNING ACROSS E TX/SE OK/EXTREME SW AR AND WILL EXPAND
FARTHER EWRD TODAY...INCREASING IN INTENSITY THIS AFTERNOON AND INTO
THE EVENING WITH SOME ISOLD TSTMS POSSIBLE AS WELL. MVFR CIGS WILL
FURTHER DETERIORATE TO IFR AND POSSIBLY LIFR THIS EVENING THROUGH
THE OVERNIGHT AND CONTINUE THROUGH THE TAF PERIOD ENDING AT 14/18Z.
MODERATE TO HEAVY RAIN WILL GRADUALLY END FROM WEST TO EAST DURING
THE MORNING HRS ON SATURDAY WITH SOME LINGERING LIGHT RAIN POSSIBLE
DURING THE AFTERNOON WITH THE PASSAGE OF A COLD FRONT. S-SE WINDS
FROM 5 TO 10 KTS FOR MOST OF THE TAF PERIOD...THEN SHIFTING TO NW
WITH FROPA AND GUSTY DURG THE DAY SATURDAY. /19/

&&

.PREV DISCUSSION... /ISSUED 438 AM CST FRI DEC 13 2013/

DISCUSSION...
AIR MASS MODIFICATION IS UNDERWAY THIS MORNING...ESPECIALLY OVER E
TX/SE OK/SW AR...WHERE THE COLUMN HAS BEGUN TO SATURATE FROM THE TOP
DOWN PER THE ELEVATED ECHOES ON THE MOSAIC RADAR IMAGERY...WELL AHEAD OF
THE CLOSED LOW OVER ERN AZ. THIS LOW HAS TAPPED INTO THE SUBTROPICAL
JET FROM THE SRN PACIFIC...WITH AREAS OF -RA HAVING ALREADY REACHED
THE GROUND PER SFC OBS OVER PORTIONS OF SRN/ERN OK AND W TX. THE
EXTENSIVE AREA OF AC ATOP ALL OF THE REGION THIS MORNING HAS ACTUALLY
ALLOWED TEMPS TO RISE SLIGHTLY...WITH ALL THE AREA EXCEPT FOR THE ERN
ZONES HAVING RISEN ABOVE FREEZING. THUS...NOW EXPECTING ANY WINTRY MIX
THIS MORNING...ALTHOUGH AREAS OF -SHRA WILL INCREASE FROM THE W LATER
THIS MORNING OVER SE OK/E TX...ONCE THE MOISTENING 30-40KT SWRLY LLJ
SHIFTS E AS THE CLOSED LOW ENTERS W TX. CAN/T RULE OUT ISOLATED
THUNDER THIS AFTERNOON OVER E TX/SE OK/ADJACENT SW AR AS THE CENTER OF
THE CLOSED LOW APPROACHES...WITH THE SHORT TERM PROGS INCREASING
850-700MB LAPSE RATES TO 6-7C/KM. PW/S WILL INCREASE TO 1.2-1.4 INCHES
BY THIS EVENING...WITH ANY EMBEDDED THUNDER ENHANCING RAIN
RATES...WITH QPF TOTALS OF A HALF INCH TO AN INCH...WITH ISOLATED
HIGHER AMOUNTS POSSIBLE...ESPECIALLY OVER SW AR AND EXTREME NRN LA.

GIVEN THE SLOW SATURATION OF THE COLUMN...HAVE DELAYED MENTION OF POPS
THIS MORNING FOR THE ERN SECTIONS OF NCNTRL LA...BUT HAVE CONTINUED
THE TREND OF CATEGORICAL POPS OVER THE WRN 2/3RDS OF THE AREA THIS
AFTERNOON...EXTENDING THEM E OVER THE REMAINDER OF THE REGION TONIGHT.
MAX TEMPS TODAY ARE A TOUGH CALL...AS TEMPS WILL ONLY WARM MINIMALLY
OVER THE I-30 CORRIDOR...WITH A MARKED GRADIENT FARTHER E WHERE THE
-SHRA WILL BE LATER TO ARRIVE. TEMPS LOOK TO REMAIN STEADY
TONIGHT...WITH A SLOW FALL POSSIBLE LATE OVER THE NW ZONES AS THE
ASSOCIATED COLD FRONT APPROACHES THE I-30 CORRIDOR. THE CONVECTION
THIS EVENING WILL QUICKLY DIMINISH FROM W TO E BY 06Z...AS MUCH DRIER
AIR QUICKLY ENTRAINS E BENEATH THE OPENING TROUGH AS IT LIFTS NE
ACROSS THE MID/LOWER MS VALLEY. HAVE TAPERED POPS OFF TO LOW CHANCE
OVER ALL BUT THE ERN ZONES AFTER 06Z...WITH -RA/-DZ POSSIBLE NEAR THE
FRONTAL ZONE. THE SHORT TERM PROGS CONTINUE TO SUGGEST VERY LIGHT QPF
OVER MUCH OF THE AREA SATURDAY...POSSIBLY ASSOCIATED WITH WEAK FORCING
NEAR THE 850MB TROUGH AS IT SHIFTS SE. IT SHOULD BE NOTED THAT A
SECOND SHORTWAVE...NOW DIGGING THROUGH WRN ID/NV THIS MORNING...WILL
FOLLOW THE HEELS OF THE INITIAL TROUGH PASSAGE TODAY/TONIGHT...AND
BECOME MORE POSITIVE TILT AS IT ENTERS THE SRN PLAINS SATURDAY
AFTERNOON. GIVEN THE SHALLOW NATURE OF THE LOW LEVEL MOISTURE...AND
WEAK FORCING ALOFT AHEAD OF THE TROUGH...THIS SECOND UPPER/850MB
TROUGH SHOULD NOT GENERATE MUCH FANFARE WITH QPF...AND HAVE MENTIONED
SLIGHT CHANCE POPS AREAWIDE TO COVER THIS POSSIBILITY. COULD ALSO SEE
PORTIONS OF E TX/SE OK NEAR LAKE WIND ADVISORY CRITERIA SATURDAY
AFTERNOON AS THE PRESSURE GRADIENT TIGHTENS BEHIND THE FRONT. THE
EXTENSIVE STRATUS FIELD MAY LIMIT THE EXTENT OF MIXING THOUGH...BUT
SOMETHING THE DAY SHIFT CAN EYE LATER TODAY.

THE POST-FRONTAL STRATOCU WILL GRADUALLY DIMINISH FROM NW TO SE LATE
SATURDAY NIGHT...WITH SUBFREEZING TEMPS RETURNING TO ALL BUT THE SE
SECTIONS OF NCNTRL LA SUNDAY MORNING. A MOSTLY CLEAR SKY SHOULD RETURN
BY SUNDAY AS DRIER AIR CONTINUES TO FILTER INTO THE REGION...WITH A
DRY NW FLOW ALOFT PERSISTING THROUGH AT LEAST MIDWEEK. TEMPS SHOULD
ALSO BEGIN TO MODERATE TO NEAR SEASONAL NORMS BY MONDAY...AND PERSIST
THROUGH MUCH OF THE WEEK. A LOW LEVEL RETURN FLOW SHOULD BEGIN TO
ADVECT MOISTURE BACK INTO THE REGION BY WEDNESDAY...WITH THE UPPER
FLOW BECOMING MORE SW BY LATE WEEK AHEAD OF A DEEP LONGWAVE TROUGH
WILL BEGIN TO DIG SSE INTO THE INTERMOUNTAIN W. CONVECTION LOOKS TO
INCREASE ACROSS THE REGION BY THE END OF THE EXTENDED AS PERTURBATIONS
ALOFT EJECT NE AHEAD OF THE LOW...ESPECIALLY BY LATE FRIDAY/SATURDAY
AHEAD OF A STRONG ARCTIC FRONT THAT WILL APPROACH THE REGION FROM THE
NW.

PRELIMS TO FOLLOW BELOW...

15

AVIATION...
MOSTLY CIRRUS CLOUD COVER WITH A FEW MID LVL CLOUDS ACROSS AREA...WITH
LOW VFR CIGS WILL WELL WEST OF I-35. EXPECT CIGS TO ONLY GRADUALLY
LOWER AFTER DAYBREAK...WITH MVFR CIGS...AND ASSOCIATED RAIN...TO
HOLD OFF UNTIL AROUND 13/18Z. FURTHER EAST AT KELD AND KMLU...THESE
CONDITIONS SHOULD HOLD OFF UNTIL 13/21-24Z. THEN CIGS WILL QUICKLY
SATURATE AND BECOME MOSTLY IFR. RAINFALL RATES MAY BE HIGHER OVER
NORTHERN CWA...WHERE SLIGHTLY GREATER MID LVL COOLING TO CONTRIBUTE
TO ELEVATED INSTABILITY. HOWEVER...ANY THUNDER WILL BE VERY LIMITED.
PRECIP SHOULD COME TO AND END AROUND 14/06Z...HOWEVER...IFR CIGS TO
CONTINUE THRU FCST PERIOD...ALTHOUGH SOME IMPROVEMENT TO CIGS POSSIBLE
OVER EAST TX BY RIGHT AROUND 14/12Z. S-SE WINDS TO INCREASE TO 5 TO
10 KTS TODAY...SHIFTING TO NW AND GUSTY DURG THE DAY SATURDAY. /VII/

&&

.PRELIMINARY POINT TEMPS/POPS...
SHV  49  45  51  31  48 / 100 100  20  10   0
MLU  52  45  54  33  46 /  60 100  20  10   0
DEQ  42  36  44  25  47 / 100  80  20  10   0
TXK  44  39  46  27  47 / 100  90  20  10   0
ELD  47  41  49  29  45 /  80 100  20  10   0
TYR  44  42  48  28  49 / 100  60  20  10   0
GGG  45  43  49  29  49 / 100  80  20  10   0
LFK  53  47  54  31  50 /  80  80  20  10   0

&&

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

$$

24/19