941
FXUS64 KLCH 180500
AFDLCH

Area Forecast Discussion
National Weather Service Lake Charles LA
1200 AM CDT Thu Jul 18 2024

...New AVIATION...

.UPDATE...
Issued at 938 PM CDT Wed Jul 17 2024

Only minor tweaks were made to the inherited PoP grids to reflect
the lingering showers. Otherwise, the rest of the afternoon
package is on track.

The frontal boundary is stretched across parts of northern LA
through east TX with it to descend through the area going into
tomorrow. The only change to the ERO was coverage of the Marginal
Risk across the entire CWA. 24h QPF totals are in the 0.50 to 1
inch range.

&&

.SHORT TERM...
(Tonight through Friday night)
Issued at 335 PM CDT Wed Jul 17 2024

Mid-afternoon sfc analysis shows the Bermuda high pressure ridge
continuing to stretch wwd across the nrn Gulf, maintaining an
onshore low-level flow across the region. Meanwhile, a weak cool
front is noted to our north, extending from the Ohio Valley
through the Ozarks to the Red River Valley. Water vapor imagery
shows the wrn Gulf within troffing extending from the Great Lakes
sswwd. With the area remaining quite moist (regional 12z soundings
showed PWATs generally around 2 inches) and no real capping
present thanks to the trof, convection was gradually developing
across mainly the srn/ern portions of the forecast area earlier.
Meanwhile a 2nd area of convection upstream associated with an
advancing weak disturbance was noted over nern TX.

The key messaging in the short term continues to be wet weather
persisting. Today`s diurnal convection is expected to begin
petering out as we approach sunset, with a few showers/storms
possibly extending a short time after sundown. The late
evening/early overnight looks dry before a combo of factors lead
to more convection developing towards sunrise...the typical
nocturnal maritime activity develop/moving ashore across the far
srn zones, while additional activity developing with the
disturbance dropping through the trof and ahead of the
approaching sfc boundary begins impacting the far nrn zones.

High POPs are on the books again for Thursday as the sfc boundary
slips into the forecast area, adding additional lift to the
already very moist airmass (mean RH values 70 to 80 percent and
PWAT values up 2.2 inches) and nil capping. Given the potential
for slow- moving convection and the high PWATs (around the 90th
percentile per SPC raob climo), WPC has highlighted the entire
forecast area in a marginal risk for excessive rainfall for tomorrow.
With this activity not being entirely diurnally driven, high rain
chances linger right through Thursday night into early Friday
morning.

Wash, rinse, repeat for Friday as the lingering boundary, progged
to meander around the region, overhead trof axis/general mid-level
weakness and copious moisture result in yet more widespread
shower/thunderstorm activity...with the WPC maintaining the
marginal risk. Some relief looks possible for Friday night as the
trof axis finally slides ewd, with much smaller POPs in the
forecast for the nwrn zones into w-cntl LA.

With the widespread cloud cover/precip, heat index values are not
expected to meet advisory criteria at any point during the short
term.

&&

.LONG TERM...
(Saturday through next Tuesday)
Issued at 335 PM CDT Wed Jul 17 2024

A very wet and rainy longterm period is in store as a series of
shortwave trof pulses work around a low pressure center parked over
the north Central US. Buoyant and deeply moist airmass in place
ahead of these shortwave perturbations will allow widespread
convection to develop each day in southeast Texas and southwest
Louisiana. Forecast PWATs 2.00 to 2.30 inches and warm-column
soundings indicate warm-rain processes will be in place, making for
very efficient downpours. With more and more rainfall piling on
through the short and then long term periods, the threat of urban
and localized river flooding increases. The Weather Prediction
Center has placed most of the area in a Marginal Risk (1 out of 4)
of Excessive Rainfall on Saturday and the entire area in a Marginal
on Sunday. This indicates there could be rainfall rates which could
lead to aforementioned flooding concerns. With little break in the
pattern seen for Monday and Tuesday, it is likely that more
Excessive Rainfall Outlook areas will be drawn up for these days.
Keep those rain boots handy!

Widespread rain-cooled air and cloud cover will keep temperatures in
check for the weekend and start of the work week. High temps should
only top out in the upper 80s to around 90 F each day. Elevated
dewpoints, however, will keep the overnight hours feeling very warm
and muggy in the low to mid 70s.

11

&&

.AVIATION...
(06Z TAFS)
Issued at 1156 PM CDT Wed Jul 17 2024

Only minor changes in thinking per this discussion. Showers are
still lingering, however little is in the vicinity of the TAF
sites. Mostly VFR conditions are still ongoing and expected to
prevail overnight. There is the outside chance of patchy fog, with
minimal to no significant VIS restrictions likely. Going into
tomorrow morning, model guidance is hinting at showers and storms
redeveloping earlier than previously forecast, hence moving it up
in the TAFs.
Stigger/87

&&

.MARINE...
Issued at 335 PM CDT Wed Jul 17 2024

Not expecting the need for any headlines on the CWF over the next
several days.

25

&&

.PRELIMINARY POINT TEMPS/POPS...
AEX  73  90  71  85 /  40  80  70  80
LCH  76  90  74  87 /  30  80  80  90
LFT  78  92  76  89 /  10  90  70  90
BPT  76  92  74  88 /  40  70  70  90

&&

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

$$

SHORT TERM...25
LONG TERM....11
AVIATION...87