Area Forecast Discussion
Issued by NWS Shreveport, LA

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FXUS64 KSHV 032235
AFDSHV

Area Forecast Discussion
National Weather Service Shreveport LA
435 PM CST Sat Dec 3 2016

.DISCUSSION...
The latest mosaic radar imagery depicts the moderate to at times
heavy rainfall continuing to gradually shift E across the Ern
sections of Ncntrl LA late this afternoon. This has occurred as
the inverted sfc trough along the SE TX and SW LA coasts has begun
to shift E...with the strong overrunning gradually shifting E as
well. The GFS/HRRR/ECMWF have all initialized best on this sfc
trough...which suggest that it will continue to shift ENE this
evening across Srn and SE LA resulting in a decrease in the hourly
rain rates over the SE sections of Ncntrl LA. These progs also
suggest the -SHRA also diminishing across extreme NE TX/SE OK/SW
AR this evening and have thus tapered pops back to chance...with
likely/categorical pops farther E as periods of -SHRA continue to
stream NE where overrunning persists. Temps will not drop much
from the 21Z obs...remaining steady in the mid to upper 40s
overnight.

The short term progs have trended a little slower with the
primary culprit of the soaking rains...with the Wrn MX closed low
expected to dig a little farther S than earlier progged across
the Gulf of CA before drifting E across Nrn MX and approaching the
TX Big Bend region by or shortly after 12Z Monday.
Meanwhile...the shortwave noted on the water vapor loop exiting
the Rockies into the Plains this afternoon will translate E
overnight into the MS Valley Sunday...which will entrain drier air
E across extreme NE TX/SE OK/SW AR. This shortwave will also
begin to shift the H850 trough SE across E TX/N LA near the I-20
corridor before pulling up stationary Sunday evening. Sct to
numerous -SHRA look to persist along/ahead of the H850 trough
Sunday mainly over E TX/N LA...but QPF amounts will remain light.
Have lowered pops down a bit Sunday...maintaining the best pops
for the Srn half of the region. Otherwise...little if any rain is
expected farther N given the dry air entrainment...with the mostly
quiet conditions expected to continue through Sunday evening.

With the more Srn track of the closed low across Nrn MX per the
GFS/Canadian/ECMWF...the closed low is about 6 hours slower than
earlier runs in kicking NE across the region late Monday...with
diffluence expected to increase across much of TX/LA late.
Meanwhile...the aforementioned sfc trough which should drift SE
into the NW Gulf/Srn LA coast will be the focus for sfc
cyclogenesis Sunday night ahead of the approaching closed low
aloft. The sfc low remains progged to lift NE along this trough
Monday...with the warm sector expanding NNE across Srn/Cntrl LA
and MS by afternoon...just SSE of the region. Overrunning is
expected to increase once again N of the returning warm
front...with the potential for deeper convection development to
quickly develop/spread N across much of the region. Still could
see another 1-2+ inches of rain with isolated higher amounts in
excess of 3 inches Monday over portions of extreme Ern TX and much
of N LA/extreme Srn AR...which may result in a localized flash
flood threat over these areas given the widespread 2-4+ inches of
rain that has fallen thus far today over these areas. Will re-
evaluate the need for the Flash Flood Watch for these areas
during the next day or so...although dry slotting aloft ahead of
the approaching closed low will help to taper rain rates from W
to E during the afternoon. Have raised pops to high end
categorical for much of the region...before tapering pops from SW
to NE as this drier air entrains NE across the region Monday
evening.

Wrap-around low clouds look to persist across much of the region
Tuesday...resulting in continued below normal max temps. May see a
bit more warming Wednesday especially across the Srn zones before
forcing aloft increases ahead of a longwave trough that will dive
SE through the Rockies and across the Plains. Sct -SHRA remain
progged by the ECMWF to develop late Wednesday afternoon over E
TX/SW AR/SE OK before spreading across the remainder of the region
Wednesday night ahead of the associated arctic cold front that
will quickly progress SSE into the region. Although the
GFS/Canadian remain the drier solutions...they are gradually
developing/expanding light QPF over a greater area across our
region ahead of the fropa.

The coldest air of this fall season will arrive Wednesday
night/Thursday as H850 temps fall to around -5C as far S as N
TX/the AR and LA border...resulting in much below normal temps as
we end of the work week. In fact...a long duration freeze is
possible Thursday night...with temps even possibly falling into
the teens across SE OK/adjacent SW AR. Should see a gradual
modification in temps commence Friday before the next shortwave
taps low level moisture return back NNE resulting in sct -SHRA
during the mid and latter half of next weekend.

Prelims to follow below...

15

&&

.PREV DISCUSSION... /issued 1202 PM CST Sat Dec 3 2016/

AVIATION...
MVFR/IFR conditions expected to prevail throughout the 18Z TAF
pd. Rain will continue throughout the pd as well...with brief pds
of improvement in flight categories possible where rain is light.
Ely/nely winds 12-18 kts with higher gusts will diminish in speed
and gradually back around to the n after sunset and continue
through the end of the pd. /12/

&&

.PRELIMINARY POINT TEMPS/POPS...
SHV  48  52  47  50 /  90  70  70  90
MLU  48  52  48  53 / 100  70  70  90
DEQ  45  52  42  47 /  50  20  30  80
TXK  45  51  45  48 /  60  40  40  90
ELD  45  50  46  48 / 100  50  50  90
TYR  47  53  47  50 /  60  60  70  90
GGG  47  52  47  50 /  70  60  70  90
LFK  50  53  50  54 / 100  80  90  90

&&

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

$$

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