664
FXUS64 KLCH 210537
AFDLCH

Area Forecast Discussion
National Weather Service Lake Charles LA
1237 AM CDT Tue Jul 21 2026

...New DISCUSSION, AVIATION, MARINE, FIRE WEATHER...

.KEY MESSAGES...

- Tropical Storm Bertha is expected to move west near the coast of
  the northern Gulf through the end of the week. This system is
  expected to be asymmetrical with a majority of the impacts south
  of the center.

- The combination of sinking air aloft as an upper level ridge
  from the Rockies builds in and the outflow from Tropical Storm
  Bertha will bring the potential for oppressive heat Tuesday into
  Wednesday. Max afternoon heat index is expected to range from
  107 to 115 degrees. A Heat Advisory is in effect for today with
  an additional heat advisory or excessive heat warning likely on
  Wednesday.

- Over the weekend the upper level ridge will continue in control
  with limited rain chances and hot conditions.

&&

.DISCUSSION...
(Today through Monday)
Issued at 1230 AM CDT Tue Jul 21 2026

Interesting set up with the newly anointed Tropical Storm Berth over
the northeast Gulf with a strengthening upper level over the
Rockies. Shear and drier air is making for a lopsided Bertha with a
majority of the convection on the south side of the storm. Over the
immediate area, dry air was noted with the precipitable water on the
21/00z upper air sounding at KLCH at near 1.30 inches.

Over the next few days there will be a battle between the
strengthening upper level ridge from the Rockies building into the
central US and the tropical system Bertha. Steering currents are
expected to take Bertha eventually westward near or just inland of
the coast of the north central and northwest Gulf.

First things first, and in the immediate term, heat will be the
issue. Looks like a combination of subsidence and sinking air from
the building upper level ridge coming down from the rockies, and the
subsident outflow on the outer west side of Bertha will bring very
hot air temperatures with highs near triple digits. Meanwhile, some
low level rich Gulf air will be trapped in place. Therefore,
expect max afternoon heat index values on Tuesday afternoon to be
around 110F degrees and in heat advisory criteria. For Wednesday,
as the low level moisture increases further and significant mixing
does not occur, the heat index has the potential to be higher
with the heat risk noted at a Major (3 out of 4) to extreme (4 out
of 4) level.

As we enter Thursday into Friday, what track and strength of Bertha
will be the main influence on the weather. Consensus shows that
shear and dry air will eventually win the battle with the official
forecast showing a weakening system along or south of the south
central and southwest Louisiana coast. All indications are that the
system will be asymmetrical with the strong northerly shear pushing
any heavy precip to the south side of the storm along with the
stronger winds. There may be a potential for some stronger showers
with high rain rates right along the coast on Thursday.

Bertha is expected to dissipate by the weekend with the upper level
ridge becoming the main weather player that will bring limited rain
chances and hot conditions.

07/Rua

&&

.AVIATION...
(06Z TAFS)
Issued at 1230 AM CDT Tue Jul 21 2026

Overnight, stable conditions can be expected with just some high
level clouds. Mainly VFR except for some patchy fog or haze with the
time of most likely MVFR conditions around sunrise or between 21/09-
13z.

Mainly dry sinking air aloft on Tuesday will provide VFR conditions.
Only caveat is after 21/19z a few showers and thunderstorms may form
with max daytime heating and a bit of a low level convergence zone
over east central and south central Louisiana. Therefore, will
mention VCTS at the KAEX/KLFT/KARA terminals.

07/Rua

&&

.MARINE...
Issued at 1230 AM CDT Tue Jul 21 2026

High pressure over the northwest Gulf and the circulation around
Tropical Storm Bertha will bring modest west northwest winds into
Wednesday. Marine conditions for Wednesday night through Friday will
depend on the eventual track and strength of Tropical Storm Bertha
as it moves just inland or over the northwest Gulf. All marine
interests should continue to monitor updates on Tropical Storm
Bertha.

&&

.FIRE WEATHER...
Issued at 1230 AM CDT Tue Jul 21 2026

Hot and humid conditions are expected across the region through
midweek. Afternoon minimum RH values will be in the 40 to 60 percent
range. Tropical Storm Bertha will approach the area on Thursday. At
the moment this system is expected to be asymmetrical with a
majority of the higher winds and rain amounts to the south of the
track of the center.

&&

.LCH WATCHES/WARNINGS/ADVISORIES...
LA...Heat Advisory from noon today to 7 PM CDT this evening for
     LAZ027>033-044-045-055-073-074-141>143-152>154-241>243-
     252>254.

TX...Heat Advisory from noon today to 7 PM CDT this evening for
     TXZ180-201-259>262-515-516-615-616.

GM...None.
&&

$$

PUBLIC/FIRE/MARINE...07
AVIATION...07