Area Forecast Discussion
Issued by NWS Shreveport, LA

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FXUS64 KSHV 260531
AFDSHV

Area Forecast Discussion
National Weather Service Shreveport LA
1231 AM CDT Sat May 26 2018

.AVIATION...

For the 26/06Z terminals forecast will prevail with mostly VFR
with lingering showers associated with old outflow boundaries
across North Louisiana. New development expected over Southeast
Oklahoma and into Northeast Texas and Southwest Arkansas
overnight with disturbance rounding Northeast periphery of ridge
aloft to the West. The terminals affected by the new convection
to include KTXK, KGGG, KTYR and possibly KSHV. MVFR flight
categories returning with visibility restrictions in rain and
possibly mist/BR after 26/09Z-26/12Z. Could see brief IFR near
daybreak then VFR returning by mid morning. Will enter mention of
convection earlier in the day Saturday with the position of the
upper trough of low pressure across the Central and Eastern
sections of the Four State Region. Surface winds will be light and
variable less than 7 knots through most of the forecast period
with a period of Southwest to West speeds near 7 knots early on
Saturday from mid morning to mid afternoon. /06/

&&

.PREV DISCUSSION... /issued 1136 PM CDT Fri May 25 2018/

UPDATE...
With lose of afternoon heating and a decrease in outflow
boundaries, expecting the showers and thunderstorms to slowly
decrease. However they look to return to Northern parts of the
forecast area tonight with disturbance riding around
the Northeast periphery of upper ridge from Mexico into the
Rockies and back side of the upper trough of low pressure
across the Mississippi Valley. Convection also returning during
the middle morning and early afternoon Saturday. Made adjustments
to the overnight and Saturday pops. /06/

PREV DISCUSSION... /issued 253 PM CDT Fri May 25 2018/

SHORT TERM.../Tonight through Saturday Night/

A line of showers and thunderstorms that developed along an outflow
boundary from a southeastward moving MCS across southeast OK earlier
this morning, has slightly loss its perfectly linear look late this
aftn. Though scattered showers and thunderstorms continued to affect
portions of southeast OK, northeast TX and southwest AR, with
isolated showers and thunderstorms elsewhere. Earlier this aftn,
portions of the line of storms across McCurtain County did reach
strong levels as it interacted with rather moist low levels
/dewpoints in the upper 60s to lower 70s/ with hail, wind gusts and
brief moderate rainfall being the main results, but have since
become sub-severe. Can not rule out the occasional wind gusts
that could warrant a Significant Weather Advisory or even a
Warning but a widespread severe weather threat is low.

As we continue to approach sunset, high-res solutions such as the
HRRR exhibited a waning trend though with lingering precip as we
head into the overnight hours. Thereafter, northwest flow aloft
persists and another embedded impulse could once again ignite an MCS
across southern OK, hence the mean-flow will propagate it to
across the northwest zones aoa sunrise. Will once again have to
look out for an outflow boundary that could aid in the generation
of additional isolated showers and thunderstorms that model
solutions sometimes struggle to pick up on. Elsewhere, daytime
destabilization and plentiful moisture will yield isolated showers
and thunderstorms. Just like what is expected tonight, the
convection will gradually dissipate several hours after sunset
tomorrow night.

MOS guidance overnight temps is over-doing it a bit as persistence
over the last several nights have been a few degrees cooler than
what guidance have depicted. Furthermore, guidance is also a few
degrees cooler during the day than what actually occurs. Will
therefore continue to manually tweak both the overnight and daytime
temps accordingly /overnight lows in the upper 60s to lower 70s and
daytime highs mainly in the lower 90s.

Side Note: We continue to monitor the newly upgraded Subtropical
Storm Alberto as it continues to become better defined just east of
the Yucatan Peninsula. The National Hurricane Center still has a
track that shows Alberto making landfall somewhere between southeast
LA and the FL Panhandle Monday/Tuesday. The Weather Prediction
Center still has the heaviest rainfall /4-7 inches/ across extreme
southeast LA and eastward to the remaining Gulf coast States. /29/

LONG TERM.../Sunday through Thursday/

Alberto will be approaching the northern Gulf Coast while the
ArkLaTex will still be under the influence of surface high
pressure coupled with an upper level ridge. Our region will be on
the west side of Alberto through about Wednesday before Alberto
begins to pull out of the southeast US to the northeast. With this
current forecast track, only far eastern portions of the area
will see showers and thunderstorms from Alberto.

Being on the west side of Alberto and under the influence of the
ridge aloft will allow for the area to experience compressional
heating from subsidence. The extended timeframe will see some 10 to
15 degree high temperature readings well above normal. Some
locations will be experiencing near record high temperatures towards
the latter part of the extended, if not flirting with triple digit
readings. Long range guidance keeps the area dry throughout the
period. /35/

&&

.PRELIMINARY POINT TEMPS/POPS...
SHV  70  92  69  93 /  20  30  20  20
MLU  69  91  70  90 /  30  30  20  40
DEQ  69  91  67  92 /  30  30  10  10
TXK  69  90  68  91 /  20  30  20  20
ELD  70  89  68  91 /  30  30  20  30
TYR  71  92  72  93 /  20  20  10  10
GGG  71  92  71  92 /  20  20  10  20
LFK  70  93  72  93 /  20  20  10  20

&&

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

$$

06/29/35



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