Area Forecast Discussion
Issued by NWS Shreveport, LA

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FXUS64 KSHV 280353 AAA
AFDSHV

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE SHREVEPORT LA
953 PM CST SAT DEC 27 2014

.DISCUSSION...
MOST OF THE RAIN IS NOW CONFINED TO THE ERN MOST PORTIONS OF THE
CWA...GENERALLY FROM TOLEDO BEND TO KMLU. HOWEVER...LATEST RADAR
LOOPS INDICATE THE NEXT ROUND OF RAIN IS MOVING NEWD FROM THE I-10
CORRIDOR IN TX AND SHOULD REACH OUR AREA AFTER MIDNIGHT. PRECIP
COVERAGE SHOULD CONTINUE TO GROW OVER OUR CWA THROUGH THE
OVERNIGHT AND INTO SUNDAY AS AN UPPER TROUGH OVER SW TX APPROACHES
AND ISENTROPIC ASCENT INCREASES. MAJORITY OF THE PRECIP SHOULD BE
SOUTH OF I-30. CANNOT COMPLETELY RULE OUT A LIGHT WINTRY MIX IN SE
OK/SW AR TONIGHT/EARLY SUNDAY WHERE THE COLDEST AIR/BELOW
FREEZING TEMPS SHOULD BE. HOWEVER...CURRENT THINKING IS THAT
PRECIP WILL MOST LIKELY BE SE OF THOSE AREAS SO HAVE NOT MENTIONED
ANY WINTRY PRECIP IN THE FCST.

ADJUSTED POP GRIDS THROUGH MIDNIGHT FOR THE SHORT TERM TRENDS AND TO
REFLECT THE INCOMING RAIN AFTER 06Z. OTHER MINOR ADJUSTMENTS WERE
ALSO MADE TO MIN TEMPS FOR TONIGHT AND TO ALL OF THE HOURLY GRIDS
BASED ON RECENT OBS. UPDATED TEXT PRODUCTS HAVE BEEN SENT. /09/

&&

.PREV DISCUSSION... /ISSUED 755 PM CST SAT DEC 27 2014/

AVIATION...

EXPECTING IFR TO PREVAIL WITH OCCASIONAL PERIODS OF MVFR FOR THE
TERMINAL FORECAST PERIOD THROUGH 29/00Z. RAINFALL ALONG WITH
PATCHY FOG WILL ALSO REDUCE SURFACE VISIBILITIES. DURING THE
OVERNIGHT HOURS RAINFALL WILL TAPER OFF BUT ANOTHER SERIES OF
UPPER LEVEL DISTURBANCES WILL BE MOVING OVER HEAD AND INCREASE
RAINFALL OVERNIGHT AND INTO THE LATE MORNING TO EARLY AFTERNOON
SUNDAY. WINDS WILL BE NORTHWEST TO NORTH 9-15 KNOTS AND SLOWLY
DECREASING THROUGH THE NIGHT AND REMAIN AROUND 5-10 KNOTS ON
SUNDAY. /06/

PREV DISCUSSION... /ISSUED 406 PM CST SAT DEC 27 2014/

DISCUSSION...
THE COLD FRONT HAS MARCHED E TO NEAR A RSN...TO IER...TO LOWER
TOLEDO BEND LINE AS OF 21Z...WITH CONVECTION HAVING BECOME MORE
WIDESPREAD THIS AFTERNOON ALONG THE FRONTAL SFC...AS THE AFTERNOON
SFC ANALYSIS REVEALS THAT A WEAK SFC LOW/FRONTAL WAVE HAS INDEED
DEVELOPED OVER WCNTRL LA. MESOANALYSIS INDICATES LITTLE IF ANY SFC
INSTABILITY AVAILABLE WITHIN THE SMALL WARM SECTOR OVER NCNTRL
LA...WITH THE BEST INSTABILITY /500-1500 J/KG/ CONFINED TO SW LA.
WITH THE CURRENT CONVECTION MOVING OVER NCNTRL LA...BELIEVE THAT
ANY SVR THREAT WILL BE ISOLATED...MAINLY IN THE FORM OF SMALL HAIL
AND LOCALLY GUSTY WINDS...WHICH SEVERAL REPORTS HAVE BEEN RECEIVED
THUS FAR SINCE LATE MORNING. THE FRONT SHOULD CONTINUE SE ACROSS
THE REMAINDER OF THE AREA THIS EVENING...EXITING OUR SE ZONES
BY/SHORTLY AFTER 06Z. THE PROGS DO CONTINUE TO INDICATE ISENTROPIC
FORCING ACROSS THE 295-300K SURFACES THIS EVENING ATOP THE SHALLOW
COLD DOME OVER NE TX/SE OK/SW AR...WHICH SHOULD GRADUALLY DIMINISH
AFTER 06Z. ACROSS E TX S OF I-20...THE PROGS REVEAL A MID LEVEL
DRY SLOT THAT HAS DEVELOPED OVER SCNTRL/SE TX...INDICATIVE OF THE
LACK OF SCT -SHRA OVER THESE AREAS...BUT SHOULD BE FILLED BACK IN
OVERNIGHT AS THE PRIMARY UPPER TROUGH...NOW DIGGING INTO NRN OLD
MX...APPROACHES THE RIO GRANDE VALLEY NEAR THE TX BIG BEND REGION
BY DAYBREAK SUNDAY. DYNAMIC FORCING AHEAD OF THE TROUGH SHOULD
RESULT IN ANOTHER WAVE OF -SHRA DEVELOPING LATE OVER THE
REGION...WHICH SHOULD GRADUALLY DIMINISH FROM W TO E SUNDAY
AFTERNOON AS DRY SLOTTING ALOFT BEGINS TO ADVECT E AHEAD OF THE
TROUGH AXIS.

THE -SHRA SHOULD FINALLY COME TO AN END SUNDAY EVENING OVER NCNTRL
LA...BUT THE NAM SUGGESTS THAT THE POST-FRONTAL STRATOCU FIELD MAY
LINGER SUNDAY NIGHT/MONDAY MORNING OVER SCNTRL AR/N LA/EXTREME ERN
TX...AS THIS SHALLOW POCKET OF MOISTURE BECOMES TRAPPED BENEATH A
CAPPING INVERSION...AND WEAK RIDGING AT THE SFC. THIS SHOULD BE
MIXED OUT MONDAY AFTERNOON...WITH A WSW FLOW ALOFT EXPECTED TO
PERSIST ACROSS THE SRN PLAINS/LOWER MS VALLEY NEXT WEEK. THE
GFS/ECMWF ARE IN AGREEMENT WITH AN ARCTIC AIR MASS BUILDING S INTO
THE REGION A LITTLE QUICKER THAN EARLIER ADVERTISED /MONDAY
NIGHT/...RESULTING IN MUCH BELOW NORMAL TEMPS FOR MUCH OF NEXT
WEEK. HOWEVER...THIS BULK OF THIS COLD AIR MASS WILL REMAIN TO OUR
N AND W...MODIFYING WITH TIME AS IT BUILDS INTO OUR REGION.

DRY CONDITIONS SHOULD PERSIST AS WELL...WITH THE
CANADIAN/ECMWF/GFS CLOSING THE NEXT W COAST LONGWAVE TROUGH OFF
OVER THE GREAT BASIN/SRN CA BY WEDNESDAY...BEFORE GRADUALLY
SHIFTING E ACROSS THE DESERT SW. OVERRUNNING LOOKS TO COMMENCE NEW
YEAR/S DAY ATOP THE SHALLOW COLD AIR MASS...WITH AREAS OF -SHRA
DEVELOPING/EXPANDING E ACROSS THE REGION THURSDAY AFTERNOON/NIGHT.
CAN/T RULE OUT A BRIEF WINTER MIX THURSDAY MORNING NW OF I-30
THROUGH EVAPORATIVE COOLING...BUT NOT EXPECTING ANY ACCUMULATION
BUT RATHER A WARMING OF THE COLUMN AS THIS OVERRUNNING INCREASES
FURTHER THURSDAY NIGHT/FRIDAY AS A SWRLY LLJ DEVELOPS. DID BUMP
POPS UP TO LIKELY TOWARDS THE LATTER EXTENDED...FOLLOWING THE
SLOWER ECMWF AND TAPERING POPS OFF FROM W TO E SATURDAY. SHOULD
ALSO SEE AN INCREASE IN TEMPS DUE TO THIS OVERRUNNING AS WELL BY
THE END OF THE PERIOD.

PRELIMS TO FOLLOW BELOW...

15

&&

.PRELIMINARY POINT TEMPS/POPS...
SHV  41  46  35  53  34 /  50  70  20  10   0
MLU  46  47  37  51  35 /  70  80  50  10   0
DEQ  30  48  28  50  30 /  30  20  10   0   0
TXK  37  45  32  49  31 /  40  40  10   0   0
ELD  40  45  32  49  31 /  60  60  20  10   0
TYR  36  47  31  55  35 /  30  40  10   0   0
GGG  39  46  31  53  34 /  40  60  10  10   0
LFK  42  46  35  56  37 /  60  70  20  10   0

&&

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

$$

09




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