Area Forecast Discussion
Issued by NWS Shreveport, LA

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000
FXUS64 KSHV 261305
AFDSHV

Area Forecast Discussion
National Weather Service Shreveport LA
805 AM CDT Sun Mar 26 2017

.AVIATION...
For the 26/12Z TAF period, VFR conditions observed except for LFK
as a warm front have begun to lift back north over deep east Texas
and central Louisiana. This is resulting in MVFR/IFR cigs and some
patchy fog at LFK, and expect this to prevail through late morning
with gradual lifting/scattering of this low level moisture aided by
returning southerly winds. The warm front will lift north across
all remaining terminal sites through today with lgt/vbrl winds this
morning becoming southerly around 8-12 kts with some gusts possible
during the afternoon across east Texas sites ahead of the next cold
front arrival later this evening through the overnight hours. Upper
level trough will transition across the Red River Valley with the
front and will produce increasing showers and thunderstorms, some
possibly severe mainly along and north of I-30 so most terminals
will be south of the primary threat area except for possibly the
TYR/TXK sites. Low level moisture will increase ahead of the front,
and except low ceilings to develop area wide with MVFR conditions
after midnight along with increasing southerly winds between 10-15
kts with higher gusts.

/19/

&&

.PREV DISCUSSION... /issued 543 AM CDT Sun Mar 26 2017/

DISCUSSION...
The morning sfc analysis indicates our old residual dryline extending
from near TVR SW to just N of AEX, to just S of JAS to just N of IAH
of 10Z. The 11-3.9u satellite imagery depicts areas of low stratus and
FG near and just S of this bndry, which has begun to lift N across SE
TX/Cntrl LA. Have added patchy FG to the forecast for the Srn counties
and parishes in Deep E TX/Ncntrl LA this morning, with it expected to
lift/scatter out by mid to late morning. Otherwise, the pressure
gradient will tighten by afternoon across the Srn Plains in response
to sfc cyclogenesis that will emerge E across the TX/OK Panhandles
this morning ahead of a deepening upper trough currently progressing E
through the Rockies. This trough should deepen a bit today as it
emerges out across Srn KS/OK this afternoon, allowing for the dry line
to mix E to just W of the I-35 corridor late in the day. The
strengthening pressure gradient will result in the quick nwd advance
of low level moisture across the expanding warm sector into OK/SW AR
along a warm front, which should extend from Cntrl OK SE into SE
OK/Srn AR early this evening. Although moisture return will not be
particularly deep, 0-6km deep lyr shear near 50kts and steepening
lapse rates in VC of the dryline will yield the potential for sct
supercells to develop after 21Z once the cap is able to erode as large
scale forcing increases ahead of the approaching trough. This
convection should quickly begin to advance E into SE OK/SW AR/possibly
extreme NE TX by mid to late evening, with some sustained SVR
potential given that MUCAPES increase to 1000-1500 J/kg across the
broadening warm sector. Have maintained SVR wording in the forecast
for this area this evening, although weakening instability and
the shallower moisture profile should result in a weakening trend late
this evening and especially after 06Z as the convection moves more
into NE TX/SW AR.

Low stratus will make a return N with the 40kt SWrly LLJ tonight, with
the attendant weak cold front expected to drift SE into NE TX/SW AR
Monday. Can`t rule out isolated convection developing ahead of this
front Monday morning despite the upper trough shifting ENE out of the
area by/shortly after 12Z, but will have to await afternoon heating
for more in the way of sct convection with the low level moisture
profile given additional time to deepen ahead of the front over
portions of Deep E TX and Ncntrl LA. Have kept low to mid chance pops
going over these areas, which should diminish by early evening with
the loss of heating/diminished instability. The front should drift SE
into portions of N LA and Deep E TX Monday evening before becoming
stationary, with the GFS/ECMWF suggesting weak overrunning which may
result in isolated convective redevelopment overnight through Tuesday
along/just N of the front. This bndry should begin to return back N as
a warm front Tuesday afternoon, with the warm sector expanding back N
into Srn and Ern OK into much of SW AR by early evening. While the
front may focus isolated convection Tuesday/Tuesday night, all eyes
will be on the next upper trough that will begin to deepen late Monday
over the Great Basin before entering the Srn Rockies Tuesday night.

LLJ intensification will begin Tuesday night across the Srn Plains,
with extensive convection expected ahead of the closed low over the
Wrn half of OK/W TX. This convection will spread E into SE OK/E TX
Wednesday afternoon, and across the remainder of the region Wednesday
night as it organizes into a squall line and marches E. Strong shear
and rapidly increasing deep lyr moisture/instability ahead of this
system will yield yet another round of svr convection over the area,
with damaging winds, hail, and isolated tornadoes possible. While the
GFS marches this convection quickly E out of the area Wednesday night
and significantly dry slots the region, the ECMWF is a bit more
bullish in convection redevelopment ahead of the attendant cold front
Thursday over portions of extreme Ern TX/N LA/SW AR as the core closed
low swings E across these areas. Have maintained likely pops for the
Ern zones, tapering pops down to mid and high chance farther W, before
cooler and drier air is able to filter SE behind the front in wake of
this next system. Near to slightly above normal temps with lower RH`s
are expected for the latter portions of the work week/start of the
weekend, before an increase in convection is expected by late
Saturday/Sunday ahead of the next closed low set to develop/settle S
across the Rockies. Should consistency be maintained, additional
rounds of convection (some possibly severe depending of the extent of
the returning warm sector) are possible through early next week.

Prelims to follow below...

15

&&

.PRELIMINARY POINT TEMPS/POPS...
SHV  86  65  81  61 /   0  20  30  10
MLU  83  64  82  62 /   0  20  40  20
DEQ  79  60  77  49 /  10  70  20  10
TXK  81  63  78  55 /   0  40  20  10
ELD  81  62  79  57 /   0  20  40  20
TYR  85  64  80  60 /  10  30  20  10
GGG  85  65  81  60 /   0  30  20  10
LFK  87  67  85  65 /   0  20  30  20

&&

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

$$

19/15



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