764
FXUS64 KBRO 221140 AAB
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
640 AM CDT Fri Aug 22 2025

...New AVIATION...

.DISCUSSION...
Issued at 1035 PM CDT Thu Aug 21 2025

Reduced subsidence aloft continues throughout deep south Texas as a
mid-level high pressure holds steady over the Four Corners region.
Unsettled weather remains on track for all of the CWA through this
weekend and into next Monday as troughing associated with a passing
mid/upper level disturbance persists and interacts with diurnal
instability and elevated moisture content across the region. Short
and long range models are in fair agreement that PWAT values of
generally 1.90-2.20 inches will become nearly widespread throughout
Friday, persisting through Sunday night, as a result of weak forcing
for ascent combined with an influx of tropical moisture advecting
inland off the Gulf via southeasterly winds on Saturday and
Saturday. Therefore, any convection that develops has the potential
for heavy rain, leading to the potential for nuisance flooding
during this timeframe. In addition to heavy rain, lightning and
gusty winds of 30-40 mph are likely, though isolated gusts of 50-55
mph are possible in the deepest convection as storms interact with
the mid morning/late afternoon seabreeze or remnant outflow
boundaries.

Probabilities of precipitation increase throughout Friday morning
and afternoon from north to south, maximizing at a medium to likely
(40-70%) chance for much of the region by the afternoon and early
evening hours, with the highest probabilities across the northern
and inland portions of the northern ranchlands as well as a low to
medium (30-40%) chance of convection continuing overnight. As
additional moisture arrives onshore on Saturday and Sunday, showers
and thunderstorms are expected to develop along the seabreeze
boundary throughout the morning, bringing a medium (40-60%) chance
to the coastal counties before spreading into the rest of the CWA
throughout the afternoon and evening, peaking at a medium to likely
(50-80%) chance on Saturday on Sunday across all of deep south
Texas. The highest chances on Saturday and Sunday look to be
centered near and just east of US-281/I-69C. Chances of convection
may continue overnight as well. As efficient heavy rainfall
production remains in place into next Monday, any developing
convection can quickly result in localized 0.5-1.0 inches of
rainfall. Between Friday morning and Sunday night, we expect that
most inland areas of deep south Texas will receive generally 0.5-1.5
inches, while amounts along the immediate coast may only receive up
to 0.5 inches. However, amounts may be higher locally, potentially
around 1.5-2.0 inches, or more, as a result of multiple rounds of
convection and/or slow-moving storms.

By Monday, PWAT values are expected to decrease to near normal
levels (1.7-1.8 inches) as the mid-level high pressure shifts
southeastward into southern-central Texas, though diurnal
instability, remnant moisture and lingering weak forcing could bring
an additional medium (40-60%) chance of showers and thunderstorms by
the late morning and afternoon hours. Following, chances of
afternoon seabreeze activity gradually drop off from a low to medium
(20-40%) chance on Tuesday to a low (less than 15%) chance by next
Friday as the high pressure slowly moves further south and over the
CWA. Slightly cooler than normal high temperatures over the weekend
warm back to near normal throughout next week. Mostly moderate
(level 2/4) heat risks and afternoon heat indices of 100-109 degF
return to the RGV and coastal counties by next Tuesday.

&&

.AVIATION...
(12Z TAFS)
Issued at 634 AM CDT Fri Aug 22 2025

Mostly clear skies with light and variable winds prevail across
Deep South Texas early this morning. Light northeast to east winds
will develop later this morning into the afternoon. Another round
of showers and thunderstorms are expected this afternoon into
early this evening. The latest HRRR indicates some convection
impacting HRL and MFE near sunset. MVFR conditions and stronger
wind gusts will be possible in and around convection.

&&

.MARINE...
Issued at 1035 PM CDT Thu Aug 21 2025

Mainly light to gentle southeasterly winds, variable at times, and
slight seas are expected to prevail through next week, leaving for
favorable marine conditions. Probabilities of showers and
thunderstorms increase beginning Friday morning and continuing with
a daily low to likely (20-60%) chance through Monday, followed by a
daily chance through next Thursday. Stronger convection could result
in brief periods of locally stronger winds and enhanced seas.

&&

.PRELIMINARY POINT TEMPS/POPS...
BROWNSVILLE             95  79  95  78 /  40  30  70  60
HARLINGEN               96  74  95  74 /  40  30  70  50
MCALLEN                 99  79  98  78 /  50  40  70  60
RIO GRANDE CITY         99  77  97  76 /  50  50  70  60
SOUTH PADRE ISLAND      89  81  89  81 /  20  30  50  50
BAYVIEW/PORT ISABEL     93  77  92  77 /  30  30  60  50

&&

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

$$

SHORT TERM...65-Irish
LONG TERM....65-Irish
AVIATION...63-KC