Area Forecast Discussion
Issued by NWS Shreveport, LA

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FXUS64 KSHV 202054
AFDSHV

Area Forecast Discussion
National Weather Service Shreveport LA
354 PM CDT Sun May 20 2018

.SHORT TERM.../Tonight through Monday Night/

The Ewd moving outflow bndry has slowed but continues to be
reinforced by convection this afternoon, and has reached E of a
JDD/TYR/JSO/DKR line as of 2030Z. Additional sct convection has
fired ahead of this bndry over extreme Ern TX along an axis of
theta-e advection within a moderately unstable air mass
characteristic of SBCapes of 1500-2000+ J/kg, just ahead of an upper
trough axis extending from Cntrl KS S into the Srn Plains. The
ongoing convection should begin to wind down this evening with the
loss of heating, but did retain low chance pops this evening
areawide, with mid chance pops over lower E TX per the consensus
amongst the HREF and HRRR in maintaining convection a little
longer over these areas. Am reluctant to take pops out completely
after 06Z, thus did keep slight chance pops going overnight as the
tail end of the upper trough/shear axis becomes removed from the
primary shortwave over Wrn NE as it lifts NE into the Midwest
late.

This shear axis will linger over SW AR/N LA/extreme Ern TX Monday,
and will again be the focus for mainly afternoon sct convection,
especially over the Ern half of the region. Have raised pops to
mid and high chance, especially over Scntrl AR/N LA, with
additional development primarily tied to outflow interactions
within a moderately unstable but weakly sheared air mass. Did
trend max temps a little warmer than MOS given the fact that most
areas this afternoon trended a little warmer than guidance. The
convection should again gradually diminish during the evening
Monday with the loss of heating, and thus kept slight chance to
low chance pops going in the evening in VC of the shear axis. This
feature should again play a role in sct convection development Tuesday
as it become trapped beneath an amplifying dirty upper ridge over
the Srn Plains and Mid MS Valley.

15

.LONG TERM.../Tuesday through Sunday/

A broad upper lvl ridge pattern with moisture in weak easterly flow
and diurnal nature of convection brought on by instability through
the workweek. Positioning of ridge will determine day by day
location of scattered, versus more isold convection, which will tend
to develop along peripheries of diffuse ridge center. Weak wind
shears will limit svr potential for storms, although gusty winds and
locally heavy rainfall will remain a possibility. An upper lvl
trough may try to organize over the central Gulf and drift nwd
towards the coast, which may enhance rainfall by the holiday wknd,
particularly if coupled by weak front which will attempt to move swd
towards the region. Increased overall cloud cover will bring aftn
temps back into upper 80s to around 90 on average, with overnight
lows expected to continue to prevail either side of 70 degrees.
Winds will remain mostly lgt and vrb for much of the week. /07/

&&

.PREV DISCUSSION... /issued 1256 PM CDT Sun May 20 2018/

AVIATION...
VFR conditions will continue through much of the 20/18Z TAF
period, although a band of convection continues to slowly spread E
into the Wrn sections of E TX attm along an outflow bndry, and
will likely affect the TYR/LFK terminals between 18-20Z, and
possibly GGG by mid to late afternoon as well. Have tempoed in
TSRA mention for these terminals, with brief MVFR cigs, reduced
vsbys, and locally gusty winds possible. Farther E across SW AR/N
LA, any convection will be more isolated, and have not included
mention in the remaining terminals attm. However, more sct
coverage may occur over the Delta region of NE LA, where the cu
field is deepening and an isolated TSRA has just recently
developed near TVR. This may build NNE towards MLU, but will amend
as needed. Overall, the convection should diminish this evening
with the loss of heating, with some elevated convective debris
lingering through the overnight hours. Can`t rule out patchy FG
developing by daybreak Monday over portions of E TX where it does
rain, but any reduced vsbys will quickly lift by 14Z. Afterwards,
a sct cu field should develop by late morning over portions of the
region, expanding moreso during the afternoon as isolated to
scattered convection develops once again with diurnal heating. SSW
5-8kts this afternoon, with locally higher gusts in/near the
convection, will become Lt/Vrb after 00Z. /15/

&&

.PRELIMINARY POINT TEMPS/POPS...
SHV  71  89  70  89 /  30  40  20  30
MLU  70  90  69  89 /  30  50  30  40
DEQ  66  87  66  89 /  30  30  20  20
TXK  70  88  68  87 /  30  30  20  30
ELD  69  90  67  89 /  30  50  30  30
TYR  68  89  70  88 /  40  20  10  30
GGG  69  89  69  89 /  40  20  10  30
LFK  69  90  68  89 /  40  20  10  30

&&

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

$$

15/07



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