FXUS64 KSHV 301127
AFDSHV
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SHREVEPORT LA
527 AM CST MON NOV 30 2009
.DISCUSSION...
COLD FRONT MAKING RAPID PROGRESS SE THIS MORNING...AS IT ABOUT TO EXIT
THE SE SECTIONS OF NCNTRL LA. AT 10Z...THIS FRONT EXTENDED FROM NEAR
TUP...TO TVR...TO IER TO JUST SE OF BPT. ASSOCIATED SHRA AND EMBEDDED
CONVECTION IS ALSO QUICKLY EXITING THE AREA WITH THE FROPA...AND HAVE
LOWERED POPS SIGNIFICANTLY FOR THE SRN SECTIONS OF THE AREA AS A
RESULT...AS DEEP LYR DRY AIR CONTINUES TO FILTER SE BEHIND THE
LONGWAVE TROUGH PASSAGE...WHICH WILL SHIFT E INTO THE MID-ATLANTIC AND
SE STATES BY THIS AFTERNOON. WILL SEE A QUICK DRY PERIOD DURING THE
NEXT 24 HRS AS THE SFC RIDGE BRIDGES E ACROSS THE SRN PLAINS AND MID
SOUTH TODAY...WITH THE COLD FRONT STALLING OUT OVER THE NRN GULF LATE
TONIGHT. FOCUS WILL THEN TURN TO OUR W AS THE CLOSED LOW SLOWLY DRIFTS
E ACROSS NRN MX...CROSSING THE TX BIG BEND REGION TUESDAY EVENING.
THIS SYSTEM WILL INDUCE SFC CYCLOGENESIS ALONG THE WRN PERIPHERY OF
THE STATIONARY FRONT JUST OFF OF THE DEEP S TX COAST...BEFORE TRACKING
NE ACROSS THE NWRN GULF AND INTO SCNTRL LA BY TUESDAY NIGHT AHEAD OF
THE LOW. OVERRUNNING WILL INCREASE ATOP THE CURRENT CP
AIRMASS AS EARLY AS LATE TONIGHT ACROSS THE TX HILL COUNTRY...ALTHOUGH
A TAD SLOWER THAN IN PAST MODEL RUNS. THIS OVERRUNNING WILL BE MORE
PRONOUNCED TUESDAY ACROSS MUCH OF TX INTO SRN LA...WITH THE AIR COLUMN
HAVING TO SATURATE FROM THE TOP DOWN. THUS...AREAS OF -RA WILL BECOME
MORE WIDESPREAD DURING THE AFTERNOON MAINLY S OF I-20 ACROSS E TX/N LA.
HAVE RAISED POPS TO CATEGORICAL TUESDAY NIGHT FOR MUCH OF THE
AREA...AS A 50KT SWRLY LLJ DEVELOPS ON THE SE SIDE OF THE 850MB LOW
OVER SE TX/SRN LA AND BEGINS TO LIFT NNW OVER THE REGION BENEATH
STRONG DIFFLUENCE EXPECTED TO SET UP AS A 110+KT SRLY UPPER JET LIFTS N.
WHILE THE PRIMARY SFC LOW/ATTENDANT WARM FRONT WILL REMAIN ALONG THE
SRN LA COAST TUESDAY NIGHT...THUS FOCUSING HEAVY RAINFALL OVER THESE
AREAS...A STRONG MOISTURE CONVERGENCE AXIS WILL SET UP ON THE NW SIDE
OF THE 850MB LOW FROM NCNTRL TX TO THE I-30 CORRIDOR OF NE TX/SE OK/SW
AR. STRONG DIFFLUENCE AHEAD OF THE CLOSED LOW WILL ENHANCE VERTICAL
FORCING AND YIELD PERSISTENT SHRA ATOP THE DENSE COLD AIR MASS TUESDAY
NIGHT...WHICH MAY YIELD LOCALLY HEAVY RAINFALL IN A SW TO NE BAND AS
THE 850MB LOW LIFTS NE ACROSS NE TX/N LA. HOWEVER...DRY SLOTTING
ADVECTING NWD AHEAD OF THE CENTER OF THE LOW WILL HELP DIMINISH THE
SHRA SOME FROM S TO N WEDNESDAY MORNING...WITH SHRA PERSISTING ALONG
THE NRN FRINGES OF THE 850MB LOW ALONG THE RED RIVER VALLEY OF EXTREME
NE TX/SE OK/SW AR. THUS...RAINFALL INTENSITIES/TOTALS SHOULD BEGIN TO
DECREASE...ESPECIALLY AS THE LOW BEGINS TO OPEN UP AND ACCELERATE NE
ACROSS THE TN VALLEY BY WEDNESDAY NIGHT. 850MB TEMPS/PARTIAL
THICKNESSES INDICATE COLD ADVECTION INCREASING RAPIDLY FROM THE N IN
WAKE OF THE 850MB LOW PASSAGE WEDNESDAY AFTERNOON...WITH FREEZING
LEVELS DROPPING RAPIDLY ACROSS EXTREME NE TX/SE OK/SW AR AS THE WRAP
AROUND PRECIP. BEGINS TO EXIT THE REGION. THUS...COULD SEE A BRIEF
TRANSITION OVER TO WINTRY PRECIP LATE WEDNESDAY AFTERNOON/EARLY
EVENING ACROSS THESE AREAS...BUT WILL NOT ADD MENTION IN THE FORECAST
ATTM AS MODELS CONTINUE TO FLIP FLOP ON THIS SCENARIO...AND REMAINS A
LOW CONFIDENCE RESULT CLIMATOLOGICALLY SPEAKING AS DEEP LYR COLD AIR
IS SLOWER TO FILTER S TO SUPPORT FROZEN PRECIP. GIVEN THE HIGHER
TERRAIN OF THE OUACHITAS. BUT THIS WILL CERTAINLY NEED TO BE
MONITORED...ALTHOUGH NO ACCUMULATIONS IS EXPECTED SHOULD IT OCCUR.
QUITE A RANGE IN THE MEDIUM RANGE SOLUTIONS BEYOND FRIDAY IN WAKE OF
THE ADDITIONAL COLD AIR THAT WILL SPILL SWD ACROSS THE SRN
PLAINS/LOWER MS VALLEY...RESULTING IN NEAR/BELOW FREEZING TEMPS
AREAWIDE THURSDAY AND FRIDAY MORNINGS. THE ECMWF IS MUCH COLDER IN BRINGING
AN ADDITIONAL ARCTIC AIR SURGE SWD ACROSS THE REGION FRIDAY...KEEPING
THE SRN PLAINS/LOWER MS VALLEY IN THE DEEP FREEZE NEXT WEEKEND.
MEANWHILE...THE GFS REMAINS PERSISTENT WITH A SWRLY RETURN FLOW
COMMENCING LATE FRIDAY AND CONTINUING THROUGH NEXT WEEKEND. WILL NOT
MAKE ANY CHANGES TO THE EXTENDED ATTM...ALTHOUGH THE GFS HAS HAD
BETTER RUN TO RUN CONSISTENCY THE LAST FEW DAYS REGARDING THIS
SCENARIO.
PRELIMS TO FOLLOW BELOW...
15
&&
.AVIATION...
EARLY THIS MORNING A COLD FRONT EXTENDED FROM NEAR TUPELO TO
VICKSBURG MISSISSIPPI...ALEXANDRIA AND DE RIDDER LOUISIANA...AND
BEAUMONT TEXAS. A NEARLY 15 MILE WIDE BAND OF SHOWERS AND ISOLATED
THUNDERSTORMS WAS OCCURRING NEAR THE SURFACE BOUNDARY...WHILE A
NEARLY 70 MILE WIDE AREA OF RAIN AND EMBEDDED SHOWERS EXTENDED IN
WAKE OF THE SURFACE BOUNDARY ACROSS PARTS OF DEEP EAST
TEXAS...NORTHWEST AND NORTH CENTRAL LOUISIANA...AND SOUTH CENTRAL
AND SOUTHEAST ARKANSAS. MVFR TO IFR FLIGHT CATEGORIES EXTENDED FROM
NEAR THE FRONTAL BOUNDARY BACK TO NEAR THE INTERSTATE 30 CORRIDOR OF
SOUTHWEST ARKANSAS AND NORTHEAST TEXAS WHICH WILL AFFECT ALL OF THE
TERMINAL FORECAST SITES ACROSS THE FOUR STATE REGION NEAR THE
ISSUANCE OF THE TERMINAL FORECASTS THIS MORNING AT 30/12Z. AS HIGH
PRESSURE BUILD SOUTH ACROSS THE FOUR STATE REGION...DRIER AIR WILL
ALLOW VFR CONDITIONS TO RETURN BY LATE MORNING INTO THE EARLY
AFTERNOON. WINDS IN WAKE OF THE BOUNDARY WILL BE NORTHWEST TO NORTH
WITH SPEEDS OF 10 TO 15 KNOTS WITH HIGHER GUSTS TO NEAR 20 KNOTS
THROUGH MUCH OF THE DAY...POSSIBLY TAPERING OFF NEAR 30/22Z TO NEAR
12 KNOTS. AFTER 01/00Z THE WINDS WILL START TO DECEASE AND BECOME
LIGHT NORTH TO NORTHEAST NEAR 5 KNOTS. HIGH PRESSURE WILL ADVANCE
EAST ACROSS THE MISSISSIPPI VALLEY OVERNIGHT SLIDING EAST OF THE
MISSISSIPPI RIVER TOWARD 01/08Z AND INTO THE TENNESSEE VALLEY BY
01/12Z TUESDAY...ALLOWING THE WINDS TO BECOME EAST 5 TO 10 KNOTS
FOR TUESDAY. /06/
&&
.PRELIMINARY POINT TEMPS/POPS...
SHV 58 41 53 41 50 / 0 0 50 80 60
MLU 56 40 54 43 49 / 20 0 40 80 60
DEQ 56 32 54 41 47 / 0 0 30 70 70
TXK 57 37 54 42 47 / 0 0 30 80 70
ELD 56 35 54 42 46 / 10 0 30 80 70
TYR 58 40 50 40 50 / 0 10 60 80 60
GGG 58 40 51 41 51 / 0 0 60 80 60
LFK 60 43 50 42 53 / 20 20 60 80 50
&&
.SHV WATCHES/WARNINGS/ADVISORIES...
AR...NONE.
LA...NONE.
OK...NONE.
TX...NONE.
$$
15/06
