509
FXUS64 KBRO 230347
AFDBRO

Area Forecast Discussion
National Weather Service Brownsville TX
1047 PM CDT Fri Aug 22 2025

...New DISCUSSION, MARINE...

.DISCUSSION...
Issued at 1046 PM CDT Fri Aug 22 2025

Following an active atmosphere this evening, an unsettled weather
pattern continues for deep south Texas and the Rio Grande Valley for
the remainder of this weekend and into Monday as mid/upper level
troughing persists, associated with a shortwave passing over the
region along the periphery of a mid-level high hovering over the
Four Corners region and the Desert SW. Weak forcing for ascent and
high moisture content across the CWA are expected to interact with
diurnal instability to result in showers and thunderstorms, bringing
a medium to likely each day the next 3 days: (60-70%) chance on
Saturday, 60-80% Sunday as well as on Monday (50-70%). Each day,
convection is expected to develop across the coastal counties along
the seabreeze boundary throughout mid to late morning, before
spreading across the remainder of inland deep south Texas into the
afternoon, with probabilities peaking by the late afternoon and
evening hours followed by some lingering chances overnight. The
highest probabilities are still expected to be along and just east
of US-281/I-69 C. Short and long range guidance continue to indicate
nearly widespread PWAT values of 1.9-2.2 inches by the afternoon and
evening hours during this timeframe, potentially reaching as high as
2.4 inches in some areas as influxes of tropical moisture arrive
onshore from the Gulf on Saturday and Sunday. Therefore, any
convection that develops has the potential to produce heavy rainfall
in addition to frequent lightning and gusty winds of 30-40 mph. Yet,
as detected on radar this afternoon, there is the possibility of
isolated gusts up to 50-55 mph, perhaps even higher, as deeper
convection interacts with the seabreeze boundary or other outflow
boundaries.

Between Saturday morning and Monday evening, we expect that most of
inland deep south Texas and the Rio Grande Valley will receive, in
general, an additional 0.50-1.25 inches of rainfall, while some
areas along and just east of US-281/I-69 C could see close to 1.50
inches, or more as multiple additional rounds of heavy rain and/or
slow moving storms pass through. Nuisance flooding is possible into
Monday. Since convection is not expected to produce much heavy rain
until the seabreeze reaches inland areas, the immediate Gulf
coastline may only see up to around 0.25 inches of rain.

Following, chances of daily afternoon seabreeze shower and
thunderstorm activivity gradually taper off throughout the week from
a low to medium (20-50%) chance on Tuesday and Wednesday to a low
(15-20%) chance by next Friday and Saturday as the mid-level high
pressure discussed above expands into eastern and central Texas,
gradually moving further south into southern Texas and increasing
subsidence aloft.

Below normal afternoon high temperatures through Monday are
expected, reaching into mostly the mid 90`s inland. As clouds and
chances of showers and thunderstorms gradually diminish throughout
next week, closer to normal highs return, with mid/upper 90`s to
lower 100`s likely inland while remaining in the mid/upper 80`s at
the coast. Overnight low temperatures continue in the 70`s inland to
lower 80s at the coast. Minor (level 1/4) to moderate (level 2/4)
heat risks continue as afternoon heat indices in the lower 100`s
over the weekend and Monday increase back to as high as 109 degF
across portions of the coastal counties and the Rio Grande Valley by
Tuesday.

&&

.AVIATION...
(00Z TAFS)
Issued at 614 PM CDT Fri Aug 22 2025

At this hour, showers and thunderstorms are beginning to move over
KMFE, which will bring further updates to prevailing conditions as
ceilings and visibility are likely to become MVFR, potentially
IFR, as heavy rain, in addition to lightning and some gusty
winds, arrive. Otherwise, KHRL and KBRO continue to experience
VFR conditions and light easterly winds. Within a few hours, all
terminals are expected to become VFR along with light and
variable, or calm, winds. Winds pick up back to 5-10 knots,
gusting to around 17-22 knots, by the afternoon. PROB30`s have
been added for generally the 18-00 Z timeframe tomorrow as showers
and thunderstorms develop.

&&

.MARINE...
Issued at 1046 PM CDT Fri Aug 22 2025

Mainly light and variable, gentle at times, winds are expected
through next Monday, becoming gentle to moderate by next Tuesday
along with slight (1-2 feet) seas prevailing through next week.
Probabilities of showers and thunderstorms increase to a low to
likely (30-70%) chance through Monday before gradually diminishing
throughout next week as mid-level ridging returns. Winds and seas
may be enhanced locally in and around stronger thunderstorms in
addition to heavy rain and lightning.

&&

.PRELIMINARY POINT TEMPS/POPS...
BROWNSVILLE             79  94  79  91 /  30  60  70  80
HARLINGEN               75  94  74  92 /  30  60  60  80
MCALLEN                 79  97  78  94 /  40  70  70  80
RIO GRANDE CITY         76  96  75  93 /  40  70  70  80
SOUTH PADRE ISLAND      81  88  80  88 /  40  50  70  70
BAYVIEW/PORT ISABEL     78  92  77  91 /  30  50  60  70

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...None.
&&

$$

SHORT TERM...65-Irish
LONG TERM....65-Irish
AVIATION...65-Irish