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fxus64 kshv 230257 
afdshv

Area forecast discussion
National Weather Service Shreveport la
957 PM CDT sun Sep 22 2019

Update...

Southerly flow and low cloud return will keep most overnight lows
around at least 70 degrees and perhaps a few degrees warmer at
some locations. Convection along an outflow boundary has mostly
diminished so do not expect any thunder thru at least midnight
with any lgt showers that could redevelop along outflow boundary
along Red River valley just to our west. However, as the cool
front north of this boundary begins to work towards the area,
convection may begin to increase north of I-30 just before
daybreak so have only made minor adjustments to precip far nrn
sections of region overnight./07/.

&&

Previous discussion... /issued 736 PM CDT sun Sep 22 2019/

Aviation...

Sea breeze convection to the south has completely diminished,
while a few showers persist along Red River valley to the west of
the cwa. Although these should diminish later this eve, a frontal
boundary will sag into areas near or just north of I-30 by 23/18z.
Expect tstms in ktxk area, and possibly near keld by later in the
aftn. Meanwhile, scattered sea breeze convection may reach klfk
durg aftn. Continued south breeze around 5 kts overnight beneath
veering SW winds above boundary layer may yield some MVFR cigs
late tonight, lifting to mostly sct or ocnl low VFR cigs after
23/15z./07/.

Previous discussion... /issued 430 PM CDT sun Sep 22 2019/

Short term.../tonight through Monday night/

Isolated to widely sct convection continues to build north-northeast across
portions of deep East Texas this afternoon along an h850-700 Theta-E
ridge axis, although this convection remains diurnally driven and
should diminish during the early evening. Have inserted slight
chance pops mention this evening for this area as well as portions
of wrn la, but the main focus for the short term period remains
with the sct convection developing from portions of North Texas across
srn and ern OK along a mid level Theta-E ridge axis along the base
of a deep upper trough extending from the Dakotas S into nrn OK.
This trough will advance east into the Great Lakes region tonight,
although the forcing aloft along the tail end of the trough axis
will weaken as the trough continues to pull away. Thus, convection
should remain scattered beneath the deep swrly unidirectional
flow, which should gradually build east-southeast into portions of extreme NE
Texas/southeast OK/nrn sections of SW Arkansas late tonight. Have increased pops
to high chance late across the far nrn zones, tapering pops down
to slight chance closer to the I-30 corridor of NE Texas/SW Arkansas.

The short term progs are in agreement with a weak cool front
drifting southeast into portions of cntrl and ern OK and wrn/cntrl Arkansas
late tonight/Monday morning, before becoming stationary later in
the day Monday. The southeast Continental U.S. Upper ridge anchored over Alabama/Georgia
remains progged to begin retrograding west into the lower MS valley
and into East Texas Monday, while flattening as the aforementioned
plains upper trough advances east. This ridge will effectively cease
the swd progress of the front/accompanying h850 trough, although
it will still continue to focus sct convection across the nrn
zones even as weak shortwave ripples traverse atop the ridge axis
near the stationary front/elevated Theta-E axis. Have maintained
mid and high chance pops over these areas, with isolated mainly
afternoon convection possible farther S across the remainder of East
Texas/wrn la where weak Theta-E ridging will persist along the wrn
fringes of the upper ridge axis. Have trended temps a bit cooler
than the blends/MOS across the nrn zones which will see denser
cloud cover/sct convection, but have trended near of not a tad
above the blends/MOS farther S where strong insolation exists
despite the morning low clouds expected to develop prior to
sunrise and linger through much of the morning. Much of the
convection will diminish during the evening with the loss of
heating, although the lingering sfc-h850 front will continue to
focus isolated to sct convection across the nrn zones. Have
continued mention of low to mid chance pops for these areas Monday
night, which may increase late in the period given the general
consensus with a weak ripple along the Theta-E axis.

15

Long term.../Tuesday through Sunday/

An upper ridge will continue to weaken on Tuesday while becoming
increasingly confined to the northeast Gulf of Mexico. At the
surface, a residual frontal boundary over southern Arkansas should
provide the focus for scattered to numerous showers and
thunderstorms across much of the area north of Interstate 20,
especially as a weak shortwave trough passes just north of the area.
Surface ridging just off the southeast Louisiana coast should
provide enough subsidence to keep our southern zones dry. The
frontal boundary will continue to become more diffuse, and surface
ridging will strengthen slightly across the area. A slight chance
for convection will remain possible, mainly along and north of
Interstate 30, but overall rain chances will be much lower on
Wednesday. Another cold front will move southward into Oklahoma and
Arkansas, but will likely stall near or north of Interstate 40
before moving back to the north.

Slight chance pops will persist into Thursday across southeast
Oklahoma and East Texas as a weak shortwave trough drifts northeast
along the Gulf Coast. As the trough approaches during the afternoon
hours, it may provide some enhancement to sea breeze convection
across deep East Texas and the Toledo Bend country of western
Louisiana Thursday afternoon. The vast majority of these showers and
thunderstorms should be diurnally driven and are expected to
dissipate by the early evening hours.

By Friday, a cut off trough over the Desert Southwest will open and
quickly eject northeast into Kansas. This will induce rapid surface
Lee cyclogenesis over the High Plains. Moisture should quickly surge
northward as deep southerly flow strengthens. Scattered convection
should develop along this front to our west and may affect portions
of southeast Oklahoma and East Texas late Friday. However, most of
this activity should weaken before reaching our forecast area as
large scale forcing decreases with the departing upper low and as
the surface trough retreats back westward. The best rain chances on
Friday will still be with diurnal sea breeze activity, which may be
enhanced by the increased southerly flow.

The GFS is still somewhat aggressive with quantitative precipitation forecast for next Saturday,
whereas the European model (ecmwf) is considerably drier. Both models are in decent
agreement with the southeast Continental U.S. Ridge quickly rebuilding and
expanding across the region on Saturday. Therefore, most of the area
should remain dry next weekend, with the exception of isolated
diurnal convection on Saturday.

Despite the frequent rain chances in the forecast, total rainfall
amounts are not expected to be very high or widespread. In fact,
most of the area may not receive any measurable rainfall. As the
upper ridge quickly strengthens and retrogrades overhead late next
weekend and into early next week, Summer-like heat and well above
normal temperatures should be expected.

Cn

&&

Preliminary point temps/pops...
shv 73 92 73 93 / 10 20 10 20
mlu 71 93 72 93 / 10 10 10 30
deq 72 85 71 86 / 30 50 40 50
txk 73 89 72 88 / 20 40 30 40
eld 70 90 71 88 / 10 30 30 40
tyr 75 92 74 92 / 10 20 10 10
ggg 74 91 73 92 / 10 20 10 10
lfk 73 91 72 93 / 10 20 10 10

&&

Shv watches/warnings/advisories...
Arkansas...none.
La...none.
OK...none.

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