Area Forecast Discussion
Issued by NWS Shreveport, LA

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000
FXUS64 KSHV 220536
AFDSHV

Area Forecast Discussion
National Weather Service Shreveport LA
1136 PM CST Mon Jan 21 2019

.AVIATION...
low vfr stratocu decks advancing nwd across the entire region.
SE-S winds around 10 kts over much of nrn LA and sw AR. However,
portions of ne TX including ktyr and kggg will see 15g25kt
overnight and continuing, or even increasing, durg the day Tue.
Cigs have lowered to low mvfr at klfk, and may begin to lower to
mvfr by 22/09z at ktyr, kggg, kshv, and ktxk terminas. These
clouds may rise again to low vfr by midday, but will once again
lower to mvfr as scattered showers quickly become widespread in
coverage with the approach of the cold front. Fropa to occur at
ktyr, kggg, ktxk, and possibly kshv before 23/06z. Cigs may fall
to ifr with fropa, and vsby may fall with a drizzly rain despite
the winds, which will maintain strength as they shift from south
to west, then nw, before the end of the 22/06z fcst cycle across
nw half of cwa./07/.

&&

.PREV DISCUSSION... /issued 909 PM CST Mon Jan 21 2019/

UPDATE...
Low clouds which moved into area by early evening have begun to
shift north of I-20 in stg s-se low lvl flow. Sfc winds expected
to remain over 10 mph across most of the area with continued
cloudy skies as upper lvl clouds also present. Current temps
mainly in the mid to upper 40s, and lower 50s in east TX lakes,
will likely remain nearly steady and with fcst lows mainly ranging
thru the 40s, except for lower 50s East TX. Patchy lgt rain
remains possible late tonight. No update needed attm./07/.

PREV DISCUSSION... /issued 410 PM CST Mon Jan 21 2019/

SHORT TERM.../Tonight through Wednesday/

The afternoon visible satellite imagery indicates an extensive cu
field continues to advect N into Deep E TX/Wcntrl LA attm, along
the nose of an intensifying Srly LLJ, along the Ern periphery of
the tighter pressure gradient noted on the sfc analysis over much
of the Srn Plains. The is the result of leeside sfc cyclogenesis
that continues to amplify over Ern CO, ahead of a stout upper
trough exiting the Great Basin and approaching the Four Corners
Region. This sfc low will eject slowly E into SW KS late tonight,
but help to amplify the Srly LLJ to 40-50kts over the Srn Plains,
allowing for the existing Cu field over Deep E and SE TX/SW and
WCntrl LA to quickly expand N across the remainder of the region
tonight. Even with the daytime mixing, wind speeds have remained
marginal/mostly below Lake Wind Advisory criteria across much of E
TX/SE OK/SW AR/NW LA this afternoon, thus have cancelled the
Advisory this afternoon as criteria will remain marginal over the
Wrn sections of E TX/SE OK even with the loss of mixing tonight.

The moisture profile will remain quite shallow through much of the
overnight hours, but the short term progs continue to hint at
weak/shallow isentropic forcing along the 285-290K sfcs such that
isolated areas of -RA/-DZ will be possible over much of the area
late (prior to daybreak Tuesday). Thus have continued mention of
slight chance pops over much of the area, with a small area of low
chance pops over SE OK/adjacent sections of SW AR along the nose
of the H925-850 LLJ, where moisture levels should deepen quicker
there. Min temps tonight will likely occur this evening, either
holding steady or slowly warming overnight in response to the
ongoing low level moisture/warm advection.

The aforementioned upper trough remains progged to enter the
Rockies late tonight, with a portion of this trough trying to
close up and eject NE into the Midwest Tuesday, with the trailing
trough axis SW across the OK/TX Panhandles into Ern NM. This
trough will remain positively tilted as it slowly enters the Srn
Plains Tuesday night, but will begin tapping elevated Pacific
moisture Tuesday afternoon ahead of the attendant cold front as
it quickly progresses E across much of OK/Cntrl TX. Thus, large
scale forcing will increase during the afternoon from Ncntrl TX NE
into extreme NE TX/Ern OK/Wrn AR well ahead of the trough, but in
VC of the approaching front. Have trended with mid to high chance
pops Tuesday morning along/N of the I-35 corridor, before ramping
pops up to categorical for these areas, with likely/high chance
pops farther E across Lower E TX/N LA/Scntrl AR. Did also ramp
pops up to high end categorical Tuesday night from Deep E TX/N
LA/SW AR as the rains overspread the area along/just ahead of the
frontal zone. The front remains progged to exit the area by
daybreak Wednesday, but the rains will becoming more post-frontal
Wednesday morning as the trough axis slowly drifts E into Cntrl
OK/TX. The post-frontal air mass will initially be shallow, but
the short term progs are in agreement with the deep lyr moisture
scouring E through the area just ahead of the critical thresholds
for any wintry mix over portions of E TX/NW LA/SW AR/SE OK
Wednesday morning. Thus, have not included any wintry mix in the
forecast attm. However, temps will quickly fall with the fropa
Wednesday morning, with the post-frontal rains gradually
diminishing from NW to SE during the day.

15

LONG TERM.../Wednesday Night through Sunday Night/

The base of the upper trof to be exiting the region at the start of
the pd Wednesday evening, with all areas precip-free. High pressure
at the sfc to quickly build in behind the trof. Secondary
disturbance diving down the plains will keep our region under a
broad-scale trof, which will bring another reinforcing shot of cold,
dry air Friday.

Yet another shortwave will dive sewd into central and E TX late
Friday, and model solutions differ quite a bit with respect to
moisture return ahead/with this disturbance. The Euro is very
aggressive developing a sfc trof just off of the TX Gulf Coast,
which would feed abundant moisture back into the cold air already in
place across our region. This solution would likely result in at
least a mix of rain/snow for much of Saturday. The GFS is much
drier, as no sfc trof develops, and only very light qpf results,
mainly Saturday night. Have stayed very conservative with respect to
PoPs and have opted to keep all precip in liquid form for now, and
will continue to monitor trends in the models. Sunday looks to be
dry, as nwly flow aloft and high pressure at the sfc dominate the
end of the fcst pd. /12/

&&

.PRELIMINARY POINT TEMPS/POPS...
SHV  48  64  36  43 /  20  70 100  50
MLU  44  64  43  43 /  10  50 100  90
DEQ  41  58  31  42 /  30  80  60  10
TXK  45  60  33  43 /  20  80  90  30
ELD  41  60  36  42 /  20  70 100  60
TYR  52  64  33  45 /  20  80  60  20
GGG  50  64  34  44 /  20  80 100  30
LFK  52  67  37  47 /  20  50 100  50

&&

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

$$


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