591
FXUS64 KLCH 152036
AFDLCH

Area Forecast Discussion
National Weather Service Lake Charles LA
336 PM CDT Sat Jun 15 2024

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

.SYNOPSIS...
Issued at 330 PM CDT Sat Jun 15 2024

A disturbance is expected to move gradually west across the
southern Gulf of Mexico through mid week. If this system remains
rather weak as far as low pressure goes as expected, than an
inverted trough will extend north from this system and help bring
a plume of deep highly anomalous moisture into the forecast area
that will bring about a potential for heavy rainfall and flooding.

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 6
to 10 inches along and south of the I-10 corridor through
Wednesday night, with 3 to 6 inches north of the I-10 corridor. A
Slight Risk (level 2 out of 4) Potential for Excessive Rainfall
leading to flooding is outlined for a majority of the forecast
area staring on Monday into Wednesday.

Stay tuned. If confidence in the the heavy rainfall potential
increases and the heavy rainfall regions become more fine tuned,
the Risk Potential may increase and a Flood Watch may be needed.

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 Monday night)
Issued at 330 PM CDT Sat Jun 15 2024

Drier air aloft is helping to keep any widespread shower activity
from forming this afternoon. Just a few showers are noted near the
sea breeze so far in Cameron Parish.

The upper level ridge over the northwest Gulf will continue to
weaken on Sunday with the upper level ridge becoming centered
over the southeast US. This will develop a broad east to west
wind flow across the Gulf of Mexico, and this will push the
inverted trough and associated deep tropical moisture that has
been over the northwest Caribbean into the Florida area to the
west.

The deep moisture and trough will begin to reach eastern portions
of the forecast area late Sunday to allow some diurnal and sea
breeze shower and storm activity to get going, especially over
the lower Atchafalaya Basin.

The deeper moisture plume will over take the forecast area on
Monday. 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 will be between 14k-16k feet, which all means that
convection will be highly efficient warm process rain makers.

Usually in these air masses, plenty of nocturnal activity will occur
over the Gulf and right along the coast. Therefore, expect by
Monday morning to see plenty of showers and a few storms over the
coastal waters and just inland. 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. With the
expected high rainfall rates in the convection, any cell mergers
or training along mesoscale boundaries, would quickly bring about
a heavy rain and flood threat. A Slight Risk (level 2 out of 4)
Potential for Excessive Rainfall leading to flooding will be
outlined for the entire forecast area on Monday.

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

Rua

&&

.LONG TERM...
(Tuesday through next Friday)
Issued at 330 PM CDT Sat Jun 15 2024

Long range pattern begins with a very stout SEly regime building in
with a notable low level jet max ~ 850mb filtering from the central
Gulf across SWLA and SETX before continuing into the Southern
Plains. Confidence has increased in seeing an active wet pattern
throughout the week as low pressure troughing continues to persist
in the western Gulf with signs of gradual deepening into the
midweek. Beyond that, the pattern remains unsettled in terms of
further organization of a closed low pressure center in the SW Gulf.
Signals for active weather along the Gulf Coast persist beyond the
long range which is congruent latest CPC analysis indicating 40 / 50
% chance of above normal precipitation continuing into the following
week.

Locally, regardless of any tropical development along the SW Gulf of
Mexico, excessive rainfall potential continues for greater portions
of SETX and SWLA given the above mentioned strong LLJ of humid
air with little inversion signals to prevent shower/storms
developing along coastal and later, further inland portions of the
CWA. Naturally, this pattern creates more uncertainty with
diurnal maximum in temperatures with some suites indicating
precipitation and thicker cloud cover to remain more prevalent
during the daytime hours. Meanwhile some guidance consolidates the
moisture according to purposed solutions in the SW Gulf. With
decent low level moisture profiles in the forecast, confidence
leans toward a wetter and slightly milder surface conditions
through Wednesday.

Marine interests should closely monitor this pattern through the
upcoming week, as headlines regarding winds and/or seas are likely
for Tuesday / Wednesday barring any major change to the current
forecast trend. Winds will have strong E - SE components making for
difficult channel navigation for large profile vessels while sea
heights may propose a threat to safe navigation to smaller vessels
along coastal waters as well.

By Thursday, overall guidance continues to keep a fairly tight
gradient of pressure along the central and western Gulf of Mexico
indicating heavier rainfall to shift NW inland toward central TX and
Southern Plains, however, despite weak lapse rates in the mid levels
remaining under 6.5C opportunities for surface based CAPE to
initiate scattered showers / storms continues, albeit to weaker POPS
trending into the weekend.

Kowalski/30

&&

.AVIATION...
(18Z TAFS)
Issued at 1226 PM CDT Sat Jun 15 2024

Dry air aloft should keep any clouds from forming into showers for
the remainder of the afternoon with any cloud ceilings from fair
weather cu staying at VFR levels.

Clear skies and light winds with VFR conditions expected tonight.

Moisture will begin to increase on Sunday, however any shower
development is expected after the end of the 18z TAF period.

Rua

&&

.MARINE...
Issued at 330 PM CDT Sat Jun 15 2024

Weak high pressure will bring about mainly light easterly winds
through the night into Sunday.

A trough will gradually move west across the southern 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, 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. Small craft advisories will
be needed during this period.

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 1 to 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.

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

Rua

&&

.PRELIMINARY POINT TEMPS/POPS...
AEX  71  94  72  86 /   0  30  20  90
LCH  75  92  75  85 /   0  40  50  90
LFT  75  92  75  86 /   0  70  60  90
BPT  75  94  76  87 /   0  30  50  90

&&

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

$$

SHORT TERM...07
LONG TERM....30
AVIATION...07