FXUS64 KSHV 251047
AFDSHV
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SHREVEPORT LA
447 AM CST WED NOV 25 2009
.DISCUSSION...
QUITE A RANGE IN TEMPS THIS MORNING...AS SOME LOCALES HAVE COMPLETELY
DECOUPLED...ALLOWING TEMPS TO PLUMMET INTO THE MID 30S ACROSS PORTIONS
OF E TX/N LA/SW AR. MEANWHILE...09Z TEMPS ARE FLIRTING WITH THE
FREEZING MARK ACROSS MCCURTAIN CO AND ADJACENT SW AR...IN THE MORE
PROTECTED AREAS. A MODEST WARMUP IS EXPECTED TODAY...AS THE WEAK COLD
ADVECTION WILL CEASE BY LATE MORNING WITH GOOD INSULATION. AM WATCHING
THE NEXT DEVELOPING LONGWAVE DIVING S OVER THE NRN PLAINS THIS
MORNING...WHICH WILL RAPIDLY PROGRESS SSE INTO THE MS VALLEY
TODAY...REINFORCING A SECONDARY SURGE OF COLD AIR S THROUGH THE AREA
THIS EVENING/OVERNIGHT. ASIDE FROM PERHAPS SOME THIN CIRRUS...COLD
ADVECTION SHOULD BE SUFFICIENT ENOUGH FOR FREEZING TEMPS TO BECOME
MORE WIDESPREAD ACROSS MCCURTAIN CO. OK INTO THE ADJACENT COUNTIES OF
SW AR OVERNIGHT...THUS WILL BE HOISTING A FREEZE WARNING FOR AREAS
MAINLY N OF AN IDABEL OK...TO FOREMAN AND NASHVILLE AR LINE FROM
04-15Z THURSDAY. PROGS INDICATING GRADIENT WINDS STAYING UP SLIGHTLY
OVERNIGHT...SUCH THAT TEMPS SHOULD REMAIN ABOVE FREEZING
ELSEWHERE...ALTHOUGH THIS WILL NEED TO BE MONITORED ACROSS PORTIONS OF
SW AR E OF TXK...WHICH ARE GENERALLY MORE PROTECTED AND COULD FALL TO
NEAR FREEZING AS WELL...AS HAS BEEN THE CASE THIS MORNING.
A DRY NW FLOW ALOFT COMMENCES THURSDAY AS THE TROUGH SWINGS E OF THE
MS...WITH A CANADIAN SFC RIDGE EXPECTED TO BUILD SE ACROSS TX AND INTO
THE REGION THURSDAY NIGHT. THUS...GOOD RADIATIONAL COOLING WILL ALLOW MIN
TEMPS FRIDAY MORNING TO BECOME EVEN COLDER AREAWIDE...WITH ADDITIONAL
FREEZE WARNINGS POSSIBLE ACROSS PORTIONS OF THE REGION. ONLY FLY IN
THE OINTMENT WILL BE THE POTENTIAL FOR THIN CIRRUS TO INCREASE FROM
THE W...AHEAD OF THE SHORTWAVE ANALYZED THIS MORNING SEVERAL HUNDRED
MILES W OF SCNTRL BAJA...WHICH IS EXPECTED TO OPEN UP AND ACCELERATE E
ACROSS NRN MX/W TX BY FRIDAY. A SSW RETURN FLOW WILL COMMENCE BY
SATURDAY AS THIS SHORTWAVE BEGINS TO TRAVERSE NE ACROSS THE
REGION...WITH THE LOW LEVEL MOISTURE DEEPENING ENOUGH SUCH THAT
ISOLATED SHOWERS MAY DEVELOP SATURDAY NIGHT AS SUBTLE PERTURBATIONS
LIFT NE IN THE DEVELOPING SW MEAN FLOW PATTERN. THIS WILL BE IN
RESPONSE TO THE NEXT LONGWAVE TROUGH EXPECTED TO DIG SSE INTO THE FOUR
CORNERS REGION/NRN MX...BEFORE SLOWLY EJECTING E ACROSS THE SRN PLAINS
EARLY NEXT WEEK. MEDIUM RANGE PROGS HAVE DEVELOPED SLIGHTLY BETTER
CONSISTENCY WITH THE PLACEMENT/MOVEMENT OF THE TROUGH...ALTHOUGH THE
ECMWF REMAINS MUCH MORE PROGRESSIVE WITH THE 850MB FROPA...QUICKLY DRY
SLOTTING THE LOWER LEVELS MONDAY IN WAKE OF THE ATTENDANT SFC FRONT.
HAVE TAILORED THE FORECAST TO A SLIGHTLY SLOWER SOLUTION...WITH
CONVECTION BECOMING WIDESPREAD LATE SUNDAY AFTERNOON/NIGHT AHEAD OF
THE FRONT...BUT COULD SEE POSTFRONTAL SHRA PERSIST THROUGH
MONDAY/MONDAY EVENING AS ADDITIONAL SHORTWAVE SPOKES ROTATE AROUND THE
CENTER OF THE COLD CORE LOW AS IT DRIFTS E ACROSS THE RED RIVER
VALLEY.
GIVEN THE EXPECTED CP INTRUSION TONIGHT/THURSDAY WELL INTO THE
GULF...THERE STILL REMAINS SOME QUESTION AS TO THE QUALITY OF GOOD
MOISTURE RETURN ACROSS THE REGION SUNDAY/SUNDAY NIGHT...WITH THE GFS
ONLY BRINGING LOWER 60 DEWPOINTS N AHEAD OF THE FRONT.
THUS...RESULTANT INSTABILITY WILL REMAIN LIMITED AS WELL...WITH ANY
POTENTIAL SVR WX THREAT REMAINING S OF THE I-20 CORRIDOR.
HOWEVER...HEAVY RAIN THREAT APPEARS THE PRIMARY THREAT ATTM...WITH
WIDESPREAD 1-3" OF QPF EXPECTED. THIS THREAT SHOULD DIMINISH FROM W TO
E MONDAY ALTHOUGH POSTFRONTAL SHRA COULD PERSIST ALONG/AHEAD OF THE
700-500MB TROUGH AXIS. IT IS INTERESTING TO NOTE THAT 850MB TEMPS ARE
COOLING QUICKLY BELOW FREEZING BENEATH THE COLD CORE LOW ACROSS MUCH
OF THE REGION BY LATE MONDAY...IN VC OF THE MID/UPPER LEVEL TROUGH
AXIS. 1000-500MB THICKNESSES NEAR 534 DAM REMAINS IMPRESSIVE AS WELL
FOR THIS TIME OF YEAR NOSING S INTO THE SRN PLAINS. THUS...FROZEN PCP CAN/T
BE RULED OUT MONDAY NIGHT/TUESDAY MORNING ACROSS PORTIONS OF THE AREA...BUT
PREFER TO SEE BETTER CONSISTENCY WITH ADDITIONAL MODEL RUNS BEFORE
COMMITTING TO THIS POSSIBILITY. CERTAINLY WILL BE INTERESTING TO SAY
THE LEAST...AS THESE PROGS HAVE BEEN INDICATING WRAP AROUND FROZEN
PCP. FOR THE LAST FEW DAYS NOW.
PRELIMS TO FOLLOW BELOW...
15
&&
.AVIATION...
MOSTLY HIGH CLOUDS STREAMING NORTHEAST THIS MORNING FROM SE TX AND
ACROSS THE LOWER MISS VALLEY. SFC HIGH PRESSURE CENTERED ACROSS THE
TX HILL COUNTRY TODAY AND THIS WILL RESULT IN NORTHWEST WINDS
CONTINUING AREA WIDE AT 5 TO 10 MPH. EXPECT VFR CONDITIONS TO
CONTINUE THROUGH THE NEXT 24 HOURS. /13/
&&
.PRELIMINARY POINT TEMPS/POPS...
SHV 64 39 62 35 66 / 0 0 0 0 0
MLU 64 38 60 34 62 / 0 0 0 0 0
DEQ 62 30 58 28 64 / 0 0 0 0 0
TXK 63 38 59 35 64 / 0 0 0 0 0
ELD 63 34 59 31 63 / 0 0 0 0 0
TYR 65 38 62 38 67 / 0 0 0 0 0
GGG 65 38 62 34 66 / 0 0 0 0 0
LFK 67 37 64 34 68 / 0 0 0 0 0
&&
.SHV WATCHES/WARNINGS/ADVISORIES...
AR...FREEZE WARNING FROM 10 PM THIS EVENING TO 9 AM CST THURSDAY FOR
THE FOLLOWING ZONES: ARZ050-051-059.
LA...NONE.
OK...FREEZE WARNING FROM 10 PM THIS EVENING TO 9 AM CST THURSDAY FOR
THE FOLLOWING ZONES: OKZ077.
TX...NONE.
&&
$$
15/13
