282
FXUS64 KLCH 112117
AFDLCH

Area Forecast Discussion
National Weather Service Lake Charles LA
417 PM CDT Sat May 11 2024

...New SHORT TERM, LONG TERM, MARINE...

.SHORT TERM...
(Tonight through Monday night)
Issued at 415 PM CDT Sat May 11 2024

A generally pleasant afternoon across the forecast area this
afternoon, with surface high pressure centered north of the region
underneath weak ridging aloft yielding light to modest easterly
winds and a fair amount of sun, though the trend of increasing cloud
cover is already underway. Temperatures across the area are
generally in the lower to mid 80s, with dew points in the upper 50s
to around 60 keeping humidity levels in the 40% range away from the
coast.

Water vapor satellite imagery clearly shows our upstream trouble
maker swirling over the Four Corners this afternoon.  This upper
trof is progged to progress slowly EWD across the central CONUS over
the next 72 hours or so, eventually resulting in a frontal passage
heading into the long term forecast.  Until then, however, a warm
air/moisture advection regime coupled with perturbations translating
through an increasingly active W/SW flow aloft will produce rounds
of showers and thunderstorms. The devil as they say is in the
details, and those are difficult to pin down.

An initial bout of showers and thunderstorms is possible as early as
tonight as the low level ridge axis continues to slide off to the
east, strengthening the warm air advection/MSTR influx across E/SE
TX as one of the aforementioned weak impulses traverses the TX
Coastal Plain into the NW Gulf.  Confidence on convective initiation
and eventual evolution is low with a wide variation in solutions
offered by guidance, thought the bulk depict little more than
isolated/scattered showers and thunderstorms.  Any activity that does
develop will lift north with time such that it would likely be north
of the area by SUN morning. Attention then shifts to a more
substantial impulse progged to pivot through the ARKLATEX SUN
afternoon/evening. If an organized/widespread rainfall event is to
transpire tomorrow, this would be the catalyst, though once again
there is decent spread in guidance. With that in mind, chose to
defer on a flood watch at this time to allow subsequent shifts to
monitor observational and guidance trends.  With that said, do not
begrudge my western/northern neighbors for issuing at this time as
there is better consensus for an axis of heavy rain within the WPC
Moderate Risk of excessive rainfall to our NW.

Something of a reprieve is expected SUN night into MON morning, with
generally good guidance consensus on a period of severe and flash
flood potential arriving MON afternoon as the combination of another
lead impulse plus the shortwave trof axis itself and associated SFC
front near the region.  Strong forcing for ascent coupled with ample
MSTR/instability will yield widespread convection ahead of and along
the frontal boundary. SPC and WPC have outlined the entire forecast
in a SLGT risk of severe and of excessive rainfall respectively. The
SFC front will progress through the area during the
evening/overnight hours.

13

&&

.LONG TERM...
(Tuesday through next Friday)
Issued at 415 PM CDT Sat May 11 2024

Moving forward into Tuesday morning, remaining showers and
thunderstorms will continue to shift east of the Mississippi with a
broad region of subsidence developing over the Southern Plains into
Central Texas throughout the day. Despite the cold front dropping
dewpoints, there will be now CAA behind the front. Thus while
conditions clear and dry out at the surface, temperatures will rise
toward upper 80s toward 90 for many locations across SETX / SWLA.
That trend follows through Wednesday.

The upper level pattern continues to develop a week ridge across the
Southern Plains while low level subsidence is more amplified along
the central Plains. Meanwhile, looking upstream across the Four
Corners region, there is a large mass of convergent air aloft begins
to increase the magnitude of the subtropical Jet over Baja and
northern Mexico. Naturally, divergence aloft over western Plains
begins to develop precipitation along a frontal boundary.
Concurrently, the sfc- 850mb lower troposphere layer continues
indicate southerly onshore flow from the ridge now shifting over
Appalachia while extending south into the eastern Gulf. Overnight
Wednesday into Thursday, a frontal boundary develops under this
scenario near the TX/LA Gulf Coast before lifting inland. Surface
troughing deepens eastward over the central plains into the
Tennessee Valley throughout the day.

Thus, as this next shortwave setups to the west, numerical guidance
has held a degree continuity of heavy precipitation potential along
Eastern TX and Central LA over the past couple days. However, the
variability of warm front will determine the placement of the
heaviest or excessive rainfall across SETX and SWLA. The National
Blend of Models has shifting some of the heavy precip over central
portions of the state, but there is much time for the evolution of
the shortwave to keep this frontal boundary further south over the
CWA. Thus, while POPs modestly increase, do expect some
variability of projected QPF until the shortwave begins to take
shape upstream during the early work week. Trend later Friday the
cold front signals the end of the precipitation for this system
with drier air moving in as yet another ridge builds west of the
Mississippi along the central Plains.

Kowalski/30

&&

.AVIATION...
(18Z TAFS)
Issued at 112 PM CDT Sat May 11 2024

VFR prevailing all sites early this afternoon, and this is
expected to generally continue through the overnight period until
lower CIGS become more prevalent MON morning KBPT and KLCH.
Easterly winds, gusty at times this afternoon at the coastal
terminals, will decrease tonight before veering more to the
southeast and increasing again on MON. In terms of convective
prospects, there is a high degree of uncertainty in terms of
initiation and evolution. It is likely that activity will develop
mid evening across E/SE TX amid a strengthening WAA regime and
subsequently lift north through the overnight hours, but the
eastward extent is uncertain. For this issuance, have included
VCSH at KBPT-KLCH-KAEX to reflect this general idea and denote the
terminals with the highest probability of seeing impacts.

13

&&

.MARINE...
Issued at 415 PM CDT Sat May 11 2024

Moderate easterly flow this gradually diminish and shift more
southeast tonight. Onshore flow will become better established on
Sunday as surface high pressure moves off to the east, and
strengthen with lower pressure developing over the plains. Onshore
flow will persist through midweek until passage of a cold front.
Shower and thunderstorm chances will increase tonight into Sunday,
with off and on rain chances expected through midweek.

13

&&

.PRELIMINARY POINT TEMPS/POPS...
AEX  83  64  77  66 /   0  30  70  70
LCH  85  68  83  73 /  10  40  70  50
LFT  85  69  86  74 /   0  30  60  60
BPT  85  70  83  74 /  10  40  80  30

&&

.LCH WATCHES/WARNINGS/ADVISORIES...
LA...None.
TX...None.
GM...None.

&&

$$

SHORT TERM...13
LONG TERM....30
AVIATION...13