Area Forecast Discussion
Issued by NWS Lake Charles, LA

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FXUS64 KLCH 150545
AFDLCH

Area Forecast Discussion
National Weather Service Lake Charles LA
1145 PM CST Thu Dec 14 2017

.DISCUSSION...
06Z Taf Issuance.

&&

.AVIATION...
Widespread cirrus continues to stream over the region, providing
BKN/OVC VFR cigs at all TAF sites. A weak cool front is moving
through the region, roughly through SE TX/SW LA approaching
Acadiana this evening. Behind it, north winds 5-8 knots
overnight, increasing to around 9-12 knots with gusts near 20
knots by 15z. VFR expected through the period.

DML

&&

.PREV DISCUSSION... /issued 957 PM CST Thu Dec 14 2017/

DISCUSSION...
Weak cold front continues to progress slowly south, currently
extending from the Acadiana region southwestward over the coastal
waters south of Cameron and Sabine Pass. Southwesterly flow aloft
will continue to bring considerable mid and high level clouds
through Friday. The cloud cover will limit any significant cooling
overnight, and despite the frontal passage, low temperatures
will likely be slightly warmer than this morning ranging from
around 40 north to the middle 40s south. Meanwhile, the persistent
cloud deck will also hinder daytime heating during the day Friday
with aftn highs in the lower to middle 50s.

Made some minor tweaks to hourly temp, dewpoint and wind grids but
overall current fcst is on track and no update is planned this
evening.

24

PREV DISCUSSION... /issued 535 PM CST Thu Dec 14 2017/

DISCUSSION...
15/00Z TAF Issuance.

AVIATION...
Widespread CI continues to stream over the region, providing
BKN/OVC VFR cigs at all TAF sites. A weak sfc front will move
through the area this evening, allowing winds to become northerly
by 06Z with sustained speeds 5-10 KT. These conditions will
continue through the day Friday as moist southwesterly flow
persists aloft in advance of a shortwave trough over TX.

24

PREV DISCUSSION... /issued 358 PM CST Thu Dec 14 2017/

DISCUSSION...
As feared in the morning update discussion, considerable and dense
cirrus over most of the area has held temperatures down a bit,
with parts of Central LA managing only the mid 50s. CDFNT has
moved little this afternoon, but remains on track to push through
the area later this evening, largely reinforcing the cool air
already in place. While moisture is quite abundant aloft,
considerable dry air in the low/mid levels and anemic lift will
result in a dry passage.

Considerable cloud cover is forecast to remain entrenched overhead
tonight and Friday as moisture depth aloft increases ahead of an
approaching northern stream upper trof. Decent lift is progged
with the trof, which will give the area a glancing shot, but the
dry air in the low to mid levels will likely prevent measurable
PCPN at the SFC over much of the inland forecast area. Moisture
quality improves over the Gulf waters, where rain chances late
tonight through Friday were largely confined. The extensive cloud
cover and CAA will hold highs tomorrow in the 50s.

FRI night into SAT AM appearing like the coldest period of the
forecast as SFC high pressure settles into the region, with
areawide 30s expected save for the immediate coast.

Southern stream trof will begin to eject out from old Mexico SAT,
inducing a weak SFC low to develop over the NW Gulf. As the trof
lifts out in a neutral/negatively tilted manner across TX toward
the ARKLATEX SAT night, the SFC low is progged to lift N along the
TX coast and through the Sabine River Valley TWD the ARKLAMISS.
Strengthening S/SW wind fields through the day SAT will result in
Gulf moisture streaming north into the region, with SFC dewpoints
rising into the mid/upper 50s by SAT night. Instability is
forecast to remain generally meager, but kinematic fields will
become quite strong and supportive of organized/possibly
severe/convection. Tornadoes and straight line winds appear at
this time to be the primary associated risks given the weak
buoyancy. A very typical low CAPE high shear severe weather
potential setup for our area this time of year. SPC has a small
portion of SE TX/SW LA outlined in a marginal risk of severe on
the Day 3 Outlook, near and generally just east of the SFC low
track in a region where inland instability is likely to reach its
maximum potential.

Regardless of severe potential, widespread showers with embedded
thunderstorms are likely to spread across the region during the
overnight hours and into SUN morning. The increase in SFC
moisture, south winds, and WAA will buoy low temperatures into the
upper 40s to mid 50s.

Model divergence begins to increase by early next week, but it is
becoming more likely that sufficient MSTR will linger across the
area to keep good rain chances in place as yet another upper trof
approaches the area on MON. Rain chances could linger into TUE and
into WED as well pending the speed/evolution of the trof.

13

MARINE...
Light winds will prevail into the evening with winds becoming
north and then increasing with a frontal passage. Small craft
advisories have been issued for the Gulf waters from late tonight
through all or part of Friday. Showers are expected late tonight
into Friday in association with the front, with north winds
gradually decreasing as high pressure settles into the region.
Onshore flow and rain chances will increase by late Saturday and
into Sunday as an upper level trough and associated surface low
move northeast across the area. A small craft advisory may be
required for the increasing east and then south winds Saturday
night.

13

&&

.PRELIMINARY POINT TEMPS/POPS...
AEX  37  54  31  58 /  10  10   0  10
LCH  45  54  39  58 /  10  10   0  10
LFT  44  54  39  58 /  10  10   0  10
BPT  45  55  39  57 /  10  10   0  20

&&

.LCH WATCHES/WARNINGS/ADVISORIES...
LA...None.
TX...None.
GM...Small Craft Advisory until 6 PM CST Friday for GMZ470-472-475.

     Small Craft Advisory until noon CST Friday for GMZ450-452-455.

&&

$$


AVIATION...08



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