437
FXUS64 KBRO 211115 AAA
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
615 AM CDT Thu Aug 21 2025

...New AVIATION...

.DISCUSSION...
Issued at 1024 PM CDT Wed Aug 20 2025

Overall, the forecast over the next 7 days remains mostly unchanged.
Subsidence aloft remains reduced over deep south Texas, allowing for
unsettled weather to continue into the beginning of next week as
mid-level troughing extends across the southern US and Gulf
states while a mid-level high pressure lingers over the Four
Corners region. This places our region near the southeastern
periphery of ridging aloft.

As such, an area of slightly enhanced ridging passing over the CWA
tonight into tomorrow may limit seabreeze convection to a low (10-
20%) chance across the mid/lower RGV and coastal counties
tomorrow afternoon. Meanwhile, there is a low to medium (20-50%)
chance across the northern ranchlands and the Rio Grande Plains as
forcing for ascent increases slightly from a weak mid-level
shortwave beginning to approach from the northeast. High
resolution models indicate increased moisture (PWAT values nearing
or exceeding 2.0 in.) as well as slow storm movement. The
combination of these two is likely to result in convection
dropping at least 0.25-0.50 inches of rain for many locations that
receive rainfall. Some areas may receive up to an inch or more.
The Weather Prediction Center (WPC) includes the northern half of
Zapata, Jim Hogg and Brooks counties, as well as the northernmost
portions of Kenedy County, within a marginal risk (level 1 of 4)
for excessive rainfall, which could result in minor instances of
flash flooding. In addition to heavy rain, deeper upscale growth
of thunderstorms on Thursday, and into the beginning of next week,
could result in lightning and gusty winds of up to 30-40 mph,
with isolated locations possibly seeing gusts up to 50-55 mph;
convection interacting with the seabreeze boundary and/or other
remnant outflow boundaries could result in stronger thunderstorms.

Friday through Sunday, the shortwave continues to slowly pass over
the region, bringing a low to likely (30-70%) chance of showers and
thunderstorms across nearly all of deep south Texas, with the
highest chances along and just east of I-69C/US-281. Elevated PWAT
values (> 2.0 in.) look to become more widespread as well over the
weekend, continuing the chance of heavy rain, potential minor flash
flooding, lightning and gusty winds. Following, the shortwave begins
to pull out, reducing PoP`s from 30-50% on Monday down to as much as
a 20-30% chance of isolated afternoon convection along seabreeze
boundaries Tuesday through Thursday of next week as the mid-level
high shifts southeastward from the Four Corners to central and
southern Texas.

Near average high temperatures (upper 90`s and lower 100`s inland)
continue for most of the forecast, despite cooling by a few
degrees over the weekend and next Monday as building clouds and
increased rain chances should keep highs in the mid to upper 90`s
for nearly all of inland deep south Texas. Highs in the mid 80`s
continue along the immediate coast in addition to warm and muggy
nights, with low temperatures falling to the mid to upper 70`s and
lower 80`s at the coast. Daily Afternoon heat indices are likely
to range between 100-107 degF across the RGV and coastal counties
through the weekend before rising back closer to 109 degF by the
beginning of next week. Minor (level 1/4) to moderate (level 2/4)
heat risks continue, becoming mostly moderate by next Tuesday.

&&

.AVIATION...
(12Z TAFS)
Issued at 614 AM CDT Thu Aug 21 2025

VFR will continue at the aerodromes through the next 24 hours.

&&

.MARINE...
Issued at 1024 PM CDT Wed Aug 20 2025

Mainly light to gentle southeasterly winds, variable at times, and
slight seas are expected to prevail, leaving for favorable marine
conditions. Probabilities of showers and thunderstorms increase
beginning late Thursday night and continuing with a daily low to
medium (20-50%) chance through Sunday. Stronger convection could
result in brief periods of locally stronger winds and enhanced
seas.

&&

.PRELIMINARY POINT TEMPS/POPS...
BROWNSVILLE             95  78  96  79 /  20  10  40  40
HARLINGEN               97  74  96  74 /  10  10  40  30
MCALLEN                100  78 100  79 /  20  10  50  40
RIO GRANDE CITY        102  77 101  77 /  20  30  50  50
SOUTH PADRE ISLAND      89  80  89  80 /  10  10  20  40
BAYVIEW/PORT ISABEL     92  77  93  77 /  10  10  30  30

&&

.BRO WATCHES/WARNINGS/ADVISORIES...None.

&&

$$