389
FXUS64 KLCH 162350
AFDLCH

Area Forecast Discussion
National Weather Service Lake Charles LA
650 PM CDT Sun Jun 16 2024

...New AVIATION...

.SYNOPSIS...
Issued at 405 PM CDT Sun Jun 16 2024

A disturbance coming out of the Central American Gyre is expected
to move gradually west-northwest across the southern and western Gulf
of Mexico through mid week. As of the last TWO, NHC has given
tropical cyclone formation for the next 48 hours at 30 percent and
through the next 7 days at 70 percent.

The consensus looks like if the system does form a closed off low
it will move into the northeast Mexico coast. However, it also
looks like it will remain sloppy with most of the higher moisture
and higher winds off and maybe well off to the north. Therefore,
impacts as far as heavy rainfall that may lead to flooding, high
wave heights, and high tides that may lead to coastal flooding are
also possible.

Both high rainfall rates and duration may be factors through mid
week, along with high tide levels along the coast not allowing for
proper drainage of river systems. Reasonable rainfall totals of 5
to 8 inches for lower southeast Texas and lower southwest
Louisiana through Wednesday night, with 2 to 4 for the remainder
of the forecast area. A Moderate Risk of Excessive Rainfall (Level
3 of of 4) is outlined for that lower southeast Texas and
southwest Louisiana area, with greater potential from Tuesday
morning through Tuesday night. If this risk continues then a Flash
Flood Watch will be issued as we get closer to the event and
confidence grows in the flood potential.

There will also be increased winds and seas over the coastal
waters, along with increased in tides and potential for coastal
flooding. Please see the marine section for more details.

Rua

&&

.SHORT TERM...
(Tonight through Tuesday night)
Issued at 405 PM CDT Sun Jun 16 2024

Forecast in the short term will depend on how the disturbance in
the southern Gulf develops over the period. For now will go with
the scenario that system remains sloppy with best moisture plume
extending well off to the north.

The upper level ridge over the northwest Gulf continues to weaken
today allowing highly anomalous moisture to move into the forecast
area. This moisture has already worked with daytime heating and
the sea breeze to produce shower and storm activity. This activity
is expected to weaken this evening with the loss of daytime
heating.

Rich Gulf moisture will hang around into Monday allowing for
widespread shower and storm activity to develop by mid to late
morning and expand during the afternoon. Heavy rainfall will be
the main concern from the activity with a quick 1 to 2 inches in a
short period will be possible.

The deeper tropical moisture plume will over take the forecast
area on Tuesday. The air mass will definitely have a tropical
origin to it with highly anomalous moisture values. Precipitable
Water values will range from 2.2 to 2.5 inches which is well above
the 90th percentile for this time of year of around 2 inches, and
closer to max moving averages and daily highs. Also, 1000-500
mean layer relative humidity values will be over 90 percent and
warm cloud layer depth will be between 14k-16k feet, which all
means that convection will be highly efficient warm process rain
makers.

Right now, the higher moisture values are focusing on lower
southeast Texas and lower southwest Louisiana, where also the
better 85H-70H southeast flow will be parallel to the developing
theta-e ridge, allowing for a possibility of training. With these
possibilities a Moderate Risk (level 3 out of 4) is already
outlined for that area, and a flash flood watch may be needed as
we near closer to the event.

Usually in these air masses, plenty of nocturnal activity will occur
over the Gulf and right along the coast. Therefore, expect plenty
of showers and a few storms over the coastal waters and just
inland during the overnight hours. With low convective
temperatures, this activity will spread quickly inland through the
morning hours and continue into the afternoon before some
decrease in activity during the evening with loss of any daytime
heating.

Some breezy winds may occur right along the coast, and also during
any convection some of the stronger winds may be brought down to
the surface.

If there is some good news, high temperatures should be a little
below normal and stay in the 80s.

Rua

&&

.LONG TERM...
(Wednesday through next Saturday)
Issued at 405 PM CDT Sun Jun 16 2024

The start of the longterm period carries the remainder of widespread
showers and thunderstorms from disturbance navigating the western
Gulf of Mexico. Regardless of whether a closed low pressure center
develops in the short term, guidance continues the trend of pushing
this system into either eastern Mexico or southeast Texas late
Wednesday into Thursday. The large northward displacement of
rainfall away from the low will be the driver for rain chances
Wednesday with some influence for Thursday. Global models keep an
airmass with PWATs well above 2.25 inches (greater than the daily
climo max) entrenched over the region in conjunction with
rainfall for at least Wednesday, thus we can expect very efficient
rain rates and flooding concerns to prevail.

High pressure ridges over the seUS and into Mississippi by Thursday.
This feature and east to northeast flow aloft will help to move some
dry(er) air into the region with forecast PWATs Thursday ranging
from 1.60 to 1.75 inches in cenLA to around 2.00 inches at the
coastline. With ridge and aforementioned airmass moving in from
the north and east, the efficiency and northward extent of
convection should be limited to typical afternoon convection along
the coastline and I-10 corridor Thursday and Friday.

Longterm models continue hinting at the possibility of another
inverted trof moving along the northern Gulf of Mexico over the next
weekend. If this solution is correct, another period of heavy rain
and widespread showers and thunderstorms will be possible.

Rain-and-cloud-cooled temperatures in the 80s on Wednesday will give
way to highs closer to climate normals in the lower 90s for the
remainder of the work week and weekend.

11/Calhoun

&&

.AVIATION...
(00Z TAFS)
Issued at 650 PM CDT Sun Jun 16 2024

No significant changes to previous TAF thinking at this time. Per
local 88Ds, ongoing convection appears to be waning as heating
ceases...maintained VC mentions in the near term for all but KBPT
just in case. Next round of precip progged to begin moving inland
from the coast prior to sunrise...timed this activity south to
north beginning with VC mentions early, eventually increasing to
prevailing showers/prob30 thunder by afternoon. Otherwise outside
of thunderstorms, VFR conditions should continue per forecast
soundings/time-height sections.

25

&&

.MARINE...
Issued at 405 PM CDT Sun Jun 16 2024

A trough from a disturbance moving out of Central America will
gradually move west-northwest across the southern and western Gulf
of Mexico from early to mid week. The gradient between the trough
and high pressure to the northeast will bring moderate to strong
east to southeast winds at or above 20 knots by Monday afternoon,
that will continue through mid week. This prolonged wind field
will allow for a significant increase in wave heights and swells.
Wave heights are expected to be 4 to 8 feet on Monday increasing
to 6 to 12 feet on Tuesday and Wednesday. A small craft advisory
is in effect.

Also, with the long duration and fetch of the easterly winds,
Ekman spiral affects will allow for water piling along the coast
increasing tide levels. Tides will be around 2 feet above
astronomical predicted levels. P-ETSS guidance shows actual tide
levels during high tide times staring late Monday night through
Wednesday at 1.5 to 2.0 Mean Higher High Water (MHHW) which are in
coastal flood advisory category, with 10 percent exceedance,
reasonable highest tide levels possible, in the 2.5 to 3.5 MHHW
which would be over coastal flood warning criteria.

Currently a coastal flood advisory will be in effect for Monday
night through Wednesday, and portions of it, especially the
Cameron Parish and Jefferson County coast may be upgraded to a
coastal flood warning as we get closer to the event.

Deep moisture will also be associated with this system that will
bring widespread shower activity across the coastal waters
through mid week.

Rua

&&

.PRELIMINARY POINT TEMPS/POPS...
AEX  73  88  71  83 /  20  80  20  60
LCH  76  87  74  83 /  40  80  50  80
LFT  75  88  76  84 /  40  80  50  80
BPT  76  88  75  84 /  50  80  50  80

&&

.LCH WATCHES/WARNINGS/ADVISORIES...
LA...Coastal Flood Advisory from 1 AM Tuesday to 4 PM CDT Wednesday
     for LAZ073-074-252>254.

TX...Coastal Flood Advisory from 1 AM Tuesday to 4 PM CDT Wednesday
     for TXZ615.

GM...Small Craft Advisory from 1 PM Monday to 7 AM CDT Thursday for
     GMZ450-452-455-470-472-475.

&&

$$

SHORT TERM...07
LONG TERM....11
AVIATION...25