882
FXUS64 KBRO 281735
AFDBRO

Area Forecast Discussion
National Weather Service Brownsville TX
1235 PM CDT Thu Aug 28 2025

...New DISCUSSION, MARINE...

.KEY MESSAGES...
Updated at 1223 PM CDT Thu Aug 28 2025

 - Afternoon heat indices of 100-109 degrees F continue to result
   in moderate (level 2/4) to major (level 3/4) heat risks through
   Sunday along with mostly clear skies and dry conditions through
   Saturday.

 - Chances of showers and thunderstorms increase from low (15-20%)
   on Sunday to moderate (40-60%) next Monday and (40-50%) next Tuesday
   ahead of a series of frontal boundaries.

 - The Weather Prediction Center (WPC) includes the northern half
   of Zapata County and the northern ranchlands within a Marginal
   (level 1/4) Risk of excessive rainfall leading to isolated
   minor flooding.

&&

.DISCUSSION...
Issued at 1223 PM CDT Thu Aug 28 2025

Mid-level ridging extending from the Desert Southwest to the Gulf is
expected to maintain mostly clear skies, near to above average
temperatures and low (less than 10%) chances of rain into at least
Saturday across deep south Texas and the Rio Grande Valley. Through
Sunday, high temperatures are likely to range from the mid/upper
90`s along and east of I-69 E to near 100 degF or higher (into the
lower 100`s) to the west, with afternoon heat indices reaching up to
100-109 degF. This continues to set the stage for moderate (level
2/4) to major (level 3/4) heat risks, gradually transitioning to a
mostly moderate heat risk by Sunday. Overnight temperatures continue
to fall into the 70`s accompanied by muggy conditions.

Meanwhile, a stationary boundary over northern Texas is likely to
slowly progress southward into central Texas over the weekend as
ridging builds upstream and the jet stream begins to amplify over
the Intramountain West and the Northern Plains. As a result, PoP`s
start to increase on Sunday to a low (15-20%) chance, highest across
the northern ranchlands along and east of US-281/I-69 C. The
combination of enhanced surface convergence and elevated PWAT values
(nearing 1.9-2.0 inches) interacting with daytime instability
results in the possibility of slow moving convection producing heavy
rainfall on Sunday; WPC has outlined the northern half of Zapata
County and the rest of the northern ranchlands within a Marginal
Risk (level 1/4) of excessive rainfall, leading to the possibility
of isolated instances of minor flooding in addition to lightning and
gusty winds.

Following, clouds, moisture pooling and lift increase across all of
the CWA as the frontal boundary continues to sag southward into
southern central Texas on Monday, generating a medium (40-60%)
chance of showers and thunderstorms throughout the morning and
afternoon. Monday night into Tuesday, the polar jet stream rides
around mid-level ridging across the PNW, diving south over the
Plains, initiating a cold front and another day of moderate (40-50%)
chances of showers on Tuesday ahead of the front. Increased clouds
on Monday and Tuesday are likely to result in more seasonable
temperatures with mid/upper 90`s, however heat indices are still
expected to range around 100-109 degF on Monday with mostly moderate
heat risks across the RGV and mainly minor (level 1/4) further
north. Drier air filters into the region on Wednesday as the front
passes through. Although air temperatures will range near to
slightly below average, reduced humidity is expected to result in
afternoon heat indices of 100-105 degF with minor heat heat risks
across the entire CWA Tuesday into Thursday. Temperatures along
the immediate coastline continue to range from the low 80`s at
night to the mid/upper 80`s during the day. PoP`s across the
region continue at a low (20-30%) Wednesday and Thursday due to
easterly winds resulting in convection along the seabreeze
boundary each afternoon.

&&

.AVIATION...
(18Z TAFS)
Issued at 1201 PM CDT Thu Aug 28 2025

Light to moderate southeasterly to southerly winds are expected to
continue at all terminals throughout this afternoon at around
10-15 knots, gusting up to 20 knots. Overnight, winds gradually
diminish to light and variable by sunrise before picking back up
by Friday afternoon. VFR conditions are expected to persist
through the TAF cycle.

&&

.MARINE...
Issued at 1223 PM CDT Thu Aug 28 2025

Gentle to moderate southeasterly to southerly winds and slight to
moderate (2-3 feet) seas continue into through Sunday, becoming
mostly light to gentle (moderate in the afternoons) with slight (1-2
feet) seas by Monday. Chances of showers and thunderstorms increase
to a low to medium (20-50%) chance Sunday into Tuesday, gradually
lowering to a low to medium (20-40%) chance into Thursday.

&&

.PRELIMINARY POINT TEMPS/POPS...
BROWNSVILLE             79  95  79  96 /   0   0   0  10
HARLINGEN               76  99  76  98 /   0   0   0   0
MCALLEN                 79 103  79 102 /   0   0   0   0
RIO GRANDE CITY         77 104  76 103 /   0   0   0   0
SOUTH PADRE ISLAND      82  90  82  90 /   0   0   0   0
BAYVIEW/PORT ISABEL     79  95  78  93 /   0   0   0   0

&&

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

$$

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