Area Forecast Discussion
Issued by NWS Shreveport, LA

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FXUS64 KSHV 112142

Area Forecast Discussion
National Weather Service Shreveport LA
442 PM CDT Tue Aug 11 2020


Very uncertain terminal forecast through the next 24 hours as the
spread remains wide as to convective evolution overnight and/or
placement. Regional radar mosaic attm showing scattered pulse type
convection northwest of the I-30 Corridor that has continued
developing in the wake of a southward moving outflow boundary.
Progs are split on the progress of this boundary southward to near
the I-20 Corridor overnight before stalling with widespread
convection developing in its wake, possible affecting the
TXK/TYR/GGG and ELD terminals.

For the 00z TAF package, will only prevail VCTS with the TXK
terminal for now, delaying VCTS to closer to midnight for
TYR/GGG/SHV and ELD. Added TEMPO groups for MVFR ceilings and MVFR
VSBY restrictions through much of the late night and morning hours
on Wed for these TAF sites as well before taking out any VCTS
mention by late morning through the tail end of the TAF period.



.PREV DISCUSSION... /issued 240 PM CDT Tue Aug 11 2020/

SHORT TERM.../Tonight through Wednesday Night/

For the rest of today...showers and thunderstorms along a
shortwave moving through the area are ongoing across portions of
our far northern zones, mainly across McCurtain county as of 19z.
Expecting these to increase in coverage for areas along and north
of I-30 this afternoon. There is a chance a few storms could spill
farther to the south, but should stay to the north of I-20. The
SPC currently has most areas along and north of I-20 in a Marginal
Risk this afternoon for thunderstorms. Main threat with any of
the stronger storms will be the possibility for hail and strong

We will continue to see showers and thunderstorms through the
night, again mainly for portions north of I-20, with the greatest
chances along and north of I-30. Thunderstorms should remain sub-
severe through the night, but there will remain a chance for some
isolated stronger wind gusts and as with any thunderstorms,
dangerous lightning. Overnight temperatures will range from the
lower 70s across our northern zones, (where we will see the
ongoing convection) to the mid 70s elsewhere.

Heading into the day Wednesday, the aforementioned shortwave
trough will continue to bring showers and thunderstorms across the
northern portion of the area, once again with the greatest chances
along and north of I-30. No severe thunderstorms are expected at
this time. We will see a wide variety of afternoon high
temperatures, in part to the convection and associated cloud cover
across the northern portion of the area. For our far northern
zones, temperatures will struggle to reach the 90s, while our
southern and western zones could be pushing 100 degrees by
tomorrow afternoon. We could see a few lingering showers and
thunderstorms into Wednesday night as well, but overall the
shortwave should shift into the Lower MS Valley by Wednesday
night which will bring an end to the convection.


LONG TERM.../Thursday through Monday Night/

A broad upper trough over the Lower Ohio River Valley will tap into
diurnal instability developing a large area of convection Thursday
afternoon across the Southeast CONUS, including Southern Arkansas
and much of Louisiana. Some of this development may be enhanced
across Louisiana due to low-level southerly flow and sea breeze
influences. The GFS continues to be very aggressive with QPF and
only provides for a few hours of a break each evening, suggesting
nocturnal development of thunderstorms will occur both early Friday
morning and early Saturday morning. Large scale forcing will not be
overly strong, and without that forcing, convection tends to be
diurnally driven. Therefore, I have continued to keep PoPs limited
to the daytime hours.

The overall synoptic pattern changes very little through Sunday, so
the trend and location of diurnal convection will likely be quite
persistant. However, by Sunday, the upper ridge retrogrades to the
west and will allow an another shortwave trough and frontal boundary
to move south towards the region. As subsidence decreases, rain
chances will spread across the entire forecast area Sunday and
Monday. The highest PoPs will likely be Monday as the front and the
trough move overhead.

Daytime high temperatures in the mid to upper 90s combined with high
humidity may result in peak heat index values over 105 degrees F
areawide Thursday and Friday, which would require heat headlines.
The increased rain chances and cloud cover should help to cool
temperatures by a few degrees during the weekend, but locations
should of Interstate 20 may still flirt with Heat Advisory criteria.



SHV  77  93  75  97 /  20  20  10  20
MLU  77  95  75  96 /  10  50  20  40
DEQ  72  91  71  95 /  40  30  10  10
TXK  74  89  73  94 /  40  30  10  10
ELD  74  91  72  94 /  30  40  20  30
TYR  77  97  76  99 /  10  10   0   0
GGG  76  95  75  97 /  20  10   0  10
LFK  76  98  75 100 /  10  10   0  10




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