FXUS64 KSHV 142150
AFDSHV
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SHREVEPORT LA
350 PM CST MON DEC 14 2009
.DISCUSSION...
CONVECTION THAT TEMPORARILY DIMINISHED OVER DEEP E TX AND THE SRN
SECTIONS OF NCNTRL LA IS TRYING TO REIGNITE AGAIN THIS MID
AFTERNOON...AS A STRONG DIFFLUENT ZONE ALOFT HAS SET UP ATOP A WARM
FRONTAL BNDRY EXTENDING FROM THE TX COASTAL BEND TO NEAR IAH...NE TO
LCH TO NEAR MCB AND MEI. THIS FRONT IS PROGGED TO CONTINUE LIFTING OH
SO SLOWLY NWD OVERNIGHT...EXTENDING FROM THE LOWER TOLEDO BEND COUNTRY
INTO CNTRL LA AFTER 06Z. UNIDIRECTIONAL FLOW WILL CONTINUE ATOP THE
FRONT...ALTHOUGH THE SW LOW LEVEL 850MB FLOW IS EXPECTED TO WEAKEN AND
GRADUALLY VEER W OVERNIGHT...THUS REDUCING THE HEAVY RAIN THREAT.
GIVEN THE CURRENT LOCATION OF THE WARM FRONT...AND LIMITED AREA TO BE
AFFECTED BY HEAVY RAIN...WILL OPT NOT TO INCLUDE THE EXTREME SRN
SECTIONS OF THE FORECAST AREA IN A FFA OVERNIGHT...BUT HAVE INCREASED
POPS SIGNIFICANTLY AND MENTIONED HEAVY RAINFALL FOR AREAS S OF A
HEMPHILL TX...TO IER AND OLLA LA LINE. THESE AREAS HAVE SEEN A GOOD
1-2" OF RAIN THIS MORNING/EARLY AFTERNOON...WITH ADDITIONAL
REDEVELOPMENT LIKELY AS A SHORTWAVE STRENGTHENS AS IT DRIFTS ESE INTO
OLD MX OVERNIGHT AND SEND SUBTLE PERTURBATIONS NE ATOP THE FRONT.
MEANWHILE...IT APPEARS A PREFRONTAL TROUGH HAS DROPPED SE ACROSS NE
TX/SCNTRL AR THIS AFTERNOON...AS INDICATED BY THE NW WIND
SHIFT...ALTHOUGH THE MAIN COLD/DRY ADVECTION ASSOCIATED WITH THE COLD
FRONT LAGS A WAYS TO THE NW...EXTENDING ROUGHLY FROM S OF A SEP...TO
TRL...TO NRN MCCURTAIN COUNTY...NE TO RUE. STRONG PRESSURE RISES
BEHIND THE FRONT WILL FORCE THE BNDRY S ACROSS E TX/N LA S OF I-20
THIS EVENING/AFTER MIDNIGHT...AS LOW LEVEL CONVERGENCE WEAKENS ACROSS
THE SRN SECTIONS OF THE AREA LATE. MIN TEMPS TONIGHT/MAX TEMPS TUESDAY WILL
BE A TOUGH CALL...AND WILL OCCUR SHORTLY AFTER SUNRISE...WITH COLD
ADVECTION STRONG ENOUGH TO HOLD TEMPS EITHER STEADY OR A SLOW FALL
THROUGHOUT MUCH OF THE DAY...EXCEPT ACROSS NE TX/SE OK/SW AR...WHERE
THE CIRRUS CANOPY THINS AND ALLOWS TEMPS TO SLOWLY WARM.
WILL LIKELY CONTINUE TO SEE CIRRUS BLANKET THE REGION
WEDNESDAY/WEDNESDAY NIGHT...AS THE SHORTWAVE TO THE W OPENS UP AND
BEGINS TO EJECT NE ACROSS THE TX COASTAL BEND AND NRN GULF
THURSDAY...AHEAD OF THE NEXT SHORTWAVE THAT IS EXPECTED TO DIVE SE
ACROSS THE NRN PLAINS. MEANWHILE...STRONG CANADIAN SFC RIDGING WILL
REMAIN IN FORM CONTROL THROUGH MUCH OF THE WEEK...AS IT DRIFTS E
ACROSS THE MS VALLEY WEDNESDAY. DRY NW FLOW ALOFT WILL PERSIST
THROUGHOUT MUCH OF THE WEEK...WITH THE 06/12Z GFS BACKING OFF ON THE
AMOUNT OF COLD AIR SPILLING SWD INTO THE REGION FOR THE START OF THE
WEEKEND. HOWEVER...THE ECMWF IS A BIT MORE AMPLIFIED WITH COLD
ADVECTION SURGING SE...BUT HAVE TRENDED THE FORECAST SLIGHTLY COOLER
THAN MOS GIVEN THE CURRENT/EXPECTED SNOWPACK ACROSS THE PLAINS...AND
THE RUN TO RUN CONSISTENCY AS OF LATE WITH THE GFS. HOWEVER...THE
EXTENDED REMAINS UP FOR GRABS GIVEN THE CURRENT DISCREPANCIES...AND
SIGNIFICANT TEMPERATURE CHANGES MAY BE IN THE OFFING SHOULD THE PROGS
TREND COLDER LIKE THE ECMWF.
PRELIMS TO FOLLOW BELOW...
15
&&
.AVIATION...
A FEW SITES HAVE BEEN CLEARING THE PAST COUPLE OF HOURS...MAINLY FOR
GGG AND TYR. TXK AND SHV HAVE ALSO BEEN SEEING SOME IMPROVEMENTS THE
PAST COUPLE OF HOURS. HOWEVER...MVFR/IFR CONDITIONS CONTINUE FOR
REMAINING SITES WITH CIGS OF AROUND 1K FT OR BELOW. SCATTERED AREAS
OF SHOWERS AND THUNDERSTORMS HAVE BEEN AFFECTING LFK AND MLU THE
PAST FEW HOURS...BUT HAVE BEEN DRIFTING EAST AWAY FROM THE AREA.
TXK/GGG/TYR...AND POSSIBLY SHV SHOULD CONTINUE TO SEE VFR CONDITIONS
THROUGH MUCH OF THE FORECAST PERIOD. CONDITIONS ARE EXPECTED TO
REMAIN AROUND OR DROP BACK TO MVFR/IFR FLIGHT CATEGORIES DUE TO CIGS
BY THE EVENING AND OVERNIGHT HOURS FOR REMAINING SITES. MOST
LOCATIONS SHOULD RETURN BACK TO VFR BY MID TO LATE MORNING ON
TUESDAY. THE COLD FRONT IS NOW ENTERING THE NORTHWESTERN PORTIONS OF
THE FORECAST AREA. SOUTHERLY WINDS OVER THE AREA EARLY THIS
AFTERNOON WILL CONTINUE TO SWITCH AROUND TO THE NORTHWEST AND THEN
NORTH BY THIS EVENING AND INTO TUESDAY AS THIS COLD FRONT PASSES
THROUGH THE AREA. WINDS WILL BECOME GUSTY ON TUESDAY WITH WINDS
AROUND 8-12 KTS EXPECTED WITH HIGHER GUSTS FOR MOST LOCATIONS. /22/
&&
.PRELIMINARY POINT TEMPS/POPS...
SHV 44 49 34 53 33 / 40 20 0 0 0
MLU 45 48 34 51 34 / 50 30 0 0 0
DEQ 35 46 25 52 30 / 10 10 0 0 0
TXK 39 48 28 51 31 / 10 10 0 0 0
ELD 40 49 29 51 31 / 20 10 0 0 0
TYR 41 50 33 54 34 / 20 10 0 0 0
GGG 42 50 34 53 33 / 20 10 0 0 0
LFK 49 51 37 55 36 / 70 30 0 0 10
&&
.SHV WATCHES/WARNINGS/ADVISORIES...
AR...NONE.
LA...NONE.
OK...NONE.
TX...NONE.
&&
$$
15/22
