Area Forecast Discussion
Issued by NWS Shreveport, LA

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131
FXUS64 KSHV 161805
AFDSHV

Area Forecast Discussion
National Weather Service Shreveport LA
105 PM CDT Tue Oct 16 2018

.AVIATION...
Periods of rainfall under mostly IFR cigs, with ocnl reductions
in vsbys will continue through much of the 18Z TAF pd. Flight
categories will begin to improve just prior to sunrise as rain
begins to diminish, with some sites even bcmg VFR towards the end
of the pd. /12/

&&

.PREV DISCUSSION... /issued 1144 AM CDT Tue Oct 16 2018/

UPDATE.../Today/
Widespread rainfall associated with strong isentropic ascent
continues across the region this morning. Temps holding steady in
the mid 40s to mid 50s, with very little movement expected. For
the update, only minor adjustments made to PoPs to better match
ongoing radar trends. Temps and other aspects of the fcst seem to
be reasonably on track. /12/

&&

PREV DISCUSSION... /issued 448 AM CDT Tue Oct 16 2018/

SHORT TERM.../Today through Wednesday/

Showers remain widespread this morning across much of E TX/N LA
and extreme Srn AR, where strong overrunning has developed atop
the shallow cold air dome in place, with rain rates in the heavier
SHRA over portions of Deep E TX as much as 1.00-1.50 inches per
hour, as evidenced for the LFK obs earlier this morning. In fact,
the 12 hr rainfall totals in LFK have already topped an impressive
6.50 inches as of 0930Z! Abnormally high PW`s of 1.8-1.9 inches
remain in place across much of E TX/N LA this morning, with the
water vapor imagery depicting a deep SW flow of Pacific moisture
which continues to advect NE from TS Tara just offshore the Cntrl
MX coast ahead of the closed low over SE CA/Wrn AZ. Perturbations
in the SW flow aloft coupled with continued overrunning today will
result in rains remaining widespread over much of the region
today, although dirty ridging aloft extending from the Wrn
Atlantic across the FL peninsula into the Gulf Of MX remains
progged to begin building N across the Lower MS Valley today,
which should help gradually shift these rains NNE affecting much
of E TX/N LA/Srn AR. Have raised pops to high end categorical
today across these areas, tapering pops just a bit across the far
Nrn and Srn zones. The 00Z progs initialized somewhat well with
the axis of heavier rains this morning over Deep E TX, although
the NAM is maintaining the axis of heavier rains longer through
late afternoon as the convection remains focused along the
H925-850 trough over E TX/N LA. Meanwhile, the GFS/ECMWF weaken
this overrunning this afternoon, which seems reasonable as the
ridging aloft begins to build N over the area. However, a
localized heavy rain/minor flooding threat will exist today over E
TX/N LA as 1-2+ inch rains are possible, with the heavy rain/minor
flood threat diminishing later in the day. Given the fact that
much of these areas have received generally less than an inch of
rain over the last couple of days, will forego a Flash Flood Watch
today given the high FFG values and as rain rates should diminish
this afternoon. Weak cold advection will also continue today,
which will keep temps fairly steady through the day.

The HREF ensembles, NAM, and ECMWF continue to maintain convection
over the areas this evening near the H925-850 trough, thus have
maintained likely pops this evening for much of E TX/N LA/extreme
Srn AR before gradually diminishing late tonight. The progs also
depict some drier low level air (bndry lyr to H925) beginning to
advect S into SE OK/Nrn sections of SW AR late tonight, which will
gradually spill S into extreme NE TX/Nrn LA Wednesday. Weak
overrunning will continue Wednesday though mainly over E TX/N LA,
which may result in light QPF over these areas. Additional
elevated isentropic ascent may also affect portions of SE
OK/extreme NE TX/Adjacent SW AR Wednesday afternoon as well, even
as the drier low level air begins to deepen over these areas.
However, the post frontal clouds will limit insolation Wednesday,
with no more than a 10 degree diurnal swing in temps given the
cool, wet grounds. Thus have tapered temps a bit below MAVMOS and
closer to the METMOS/Blends Wednesday afternoon.

15

LONG TERM.../Wednesday night through Monday night/

The persistent upper level low over the SW U.S. will continue to
keep SW flow aloft over much of the area keeping rain clouds nearby
by for our Texas counties for late week as our AR/LA counties will
see drier air backdoor into the area from a 1032mb surface high
edging into the OH river valley. This chilly high pressure system
will continue drifting East quickly as a maritime surface high
pushes over the front range of the Rockies headed our way for early
on Saturday.

The renewed overrunning pattern will increase the rain coverage
spreading back Eastward Friday into Saturday ahead of the front. The
GFS and ECMWF vary a bit on the Saturday clearing line with the GFS
a little more progressive. The cut off upper low will retrograde
offshore and diminish the moisture feed temporarily. Both models
agree that Sunday is looking pretty nice with a little weaker and
less chilly air mass by comparison with recent air temperatures that
will be a little closer to normal. This Pacific air mass will
however keep the Fall-like temps in place across the region with
overnight lows in 50s and daytime highs mostly in the 60s. The
seasonal temps and continued dry weather will start the new week,
but unravel during Tuesday as the same upper low drifts back into
play for the mid South with more rainfall. /24/

&&

.PRELIMINARY POINT TEMPS/POPS...
SHV  52  51  59  55 / 100  70  30  20
MLU  53  51  60  55 / 100  70  30  10
DEQ  49  48  59  54 /  80  50  30  10
TXK  49  48  58  52 / 100  50  30  10
ELD  50  48  59  53 / 100  60  20  10
TYR  50  49  56  53 / 100  70  30  30
GGG  52  50  58  54 / 100  70  30  20
LFK  54  53  61  56 /  70  60  30  30

&&

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

$$

12/99/99



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