029
FXUS64 KLCH 202322
AFDLCH

Area Forecast Discussion
National Weather Service Lake Charles LA
622 PM CDT Thu Aug 20 2026

...New AVIATION...

.KEY MESSAGES...

- A Heat Advisory is in effect until 8 PM today for indices up to
  110F.

- An Extreme Heat Warning has been issued from Tyler county east
  to Avoyelles and St Landry from 10 AM to 8 PM. This is for high
  temperatures 103 to 105F and/or heat indices 113 to 115F.

- A Heat Advisory will be in effect for all other areas Friday
  from 10 AM to 8 PM for heat indices up to 112F and high temps
  100 to 103F.

- Heat Stress Levels will increase to Extreme (level 4 of 4) from
  southeast Texas to all of Louisiana From Friday to Monday. Major
  to Extreme levels will then continue into the week.

- A weak boundary will move through late Friday with very isolated
  showers and weakening thunderstorms possible. Lightning and
  gusty winds could exacerbate fire conditions.

- Vegetation will continue drying with these conditions. Check
  with your local officials for burn bans across SETX and CEN/SWLA.

&&

.DISCUSSION...
(This evening through next Wednesday)
Issued at 115 PM CDT Thu Aug 20 2026

Looking to the upper air map once more, there is now a bit more
activity to peruse. Upper high pressure dome has centered itself
right over the Four Corners; compressional effects from troughs on
its west and east flank causing it to amplify. Starting tonight,
we will see a battle for dominance of the north Gulf coast between
upper high and a Upper high will spin over the Desert Southwest
through the coming days as a series of weak shortwave pulses
cartwheel down its eastward edge from Friday to Sunday. Each wave
will drag southward the eastward trof little by little until the
upper jet can phase down its westward edge and carry it out on
Sunday. Upper high will then settle back into the south-central
Plains / cenTX for the rest of the period.

Now that we know the pattern at hand, let`s discuss its impacts to
seTX/swLA.

First, extreme heat. Once again, temperatures are higher by 2 to 4
degrees at this hour compared to this time yesterday. Interesting
enough, dewpoints are within 1 degree; we are less mixed. That
shows the power of a mixed surface layer!
Other obs are poking upwards as well, with peak heat index still
to come around 5 PM. Heat Advisory for indices up to 111 will go
until 8 PM.

Thermals get a bit more complicated tomorrow. As seen in recent
days` trends, temps will continue to rise faster and top out
higher. High pressure will squeeze up an over the northwest Gulf
beneath an amplifying trough in the Ohio Valley region. This act
of localized compression will offer low to mid level height rises,
increasing the volume our airmass can expand in to. Thus, we can
go ahead and anticipate high temperatures in the 98 to 104F range.
This is a typical pattern for summertime heat waves. What isn`t
typical is low to midlevel humidity persisting at 55 to 70 percent
during this daytime heating cycle. Moisture will stream in from
the northeast, blowoff from recent storm clusters in the
Midsouth.

We will dry out at the sfc layer after sunrise. But with no
pressure gradient induced by pressure features, there will be no
wind to mix out sfc humidity. In fact, any air descending from the
previously mentioned moisture layer should maintain the sfc
humidity levels.

So, Friday is setting up to be a perfect daytime steam sauna for
the region. North most zones have been placed in an Extreme Heat
Warning as indices in the 113 to 115 F range are expected.
Outside the heat index, high temperatures up to 104 are forecast,
but there exists a 20 percent chance southeast Texas to Vernon
parish could see temps 105 or greater. Whether temps top out at
103, 105 or higher, an airmass with Td>70 at peak heat would
create extremely dangerous heat conditions.

Dry air behind a weak front filters in on Saturday and Sunday
allowing Tds to mix out, limiting heat indices each day. However,
indices in the 108 to 112F are still expected.

Next. rain chances late Friday. As the boundary comes southward to
later Friday, convection is expected to accompany its travel.
Activity should begin moving into north LA in the mid afternoon
or so, with a slow progression into the evening.
Any approaching clusters should lose their steam upon arrival to
cenLA as the boundary hits local high pressure and with the loss
of daytime heating. However, as storms die, there could be a brief
period of stronger gustier winds.

Another lower chance, but still hazardous scenario, will be if any
storms maintain themselves and cast off lightning. Ground fuels
are dry and cured, so would light easily. And with breezy winds
possible too, a wildfire scenario may manifest.

Once again Saturday and beyond, high pressure is in control but
with less strength. Hot and dry to continue.

11/Calhoun

&&

.AVIATION...
(00Z TAFS)
Issued at 622 PM CDT Thu Aug 20 2026

VFR conditions will continue over night and into tomorrow morning.
During the afternoon scatted showers and thunderstorms will form
across the region.

&&

.MARINE...
Issued at 115 PM CDT Thu Aug 20 2026

Surface ridging extending over the entire Gulf will keep
conditions over the waters mostly clear of rain chances and with
low, onshore winds and seas.

&&

.FIRE WEATHER...
Issued at 115 PM CDT Thu Aug 20 2026

There is less than a 20 percent chance of showers and storms as a
weak boundary moves north to south through the area late Friday.
Primary concern is for lightning strikes which may light dry
ground fuels, a secondary concern will be for any outflow winds
which could cause any ongoing fires to become volatile.

The hottest days of this heat wave are anticipated to begin Friday
and continue through the weekend. High temps in the 100 to 104 F
range are possible for areas north of HWY 190. Moisture will very
weakly stream inland over the weekend as high pressure does keep a
fetch off the Gulf, but the inland extent of any appreciable
humidity will be limited. Daily minimum RH values will range from
30 to 40 percent north of 190 and 40 to 40 percent south to the
coast.

&&

.LCH WATCHES/WARNINGS/ADVISORIES...
LA...Heat Advisory until 8 PM CDT this evening for LAZ027>033-044-045-
     055-073-074-141>143-152>154-241>243-252>254.

     Extreme Heat Warning from 10 AM to 8 PM CDT Friday for
     LAZ027>029-032-033.

     Heat Advisory from 10 AM to 8 PM CDT Friday for LAZ030-031-044-
     045-055-073-074-141>143-152>154-241>243-252>254.

TX...Heat Advisory until 8 PM CDT this evening for TXZ180-201-259>262-
     515-516-615-616.

     Extreme Heat Warning from 10 AM to 8 PM CDT Friday for TXZ180-
     259-260.

     Heat Advisory from 10 AM to 8 PM CDT Friday for TXZ201-261-262-
     515-516-615-616.

GM...None.
&&

$$

PUBLIC/FIRE/MARINE...11
AVIATION...14