792
FXUS64 KBRO 300521
AFDBRO

Area Forecast Discussion
National Weather Service Brownsville TX
1121 PM CST Sat Nov 29 2025

...New KEY MESSAGES, DISCUSSION, AVIATION, MARINE...

.KEY MESSAGES...
Updated at 1113 PM CST Sat Nov 29 2025

* Big changes to the weather pattern in store as a strong cold
  front tonight into Sunday will bring a notably cooler airmass
  (potentially the coldest since last February) to the region
  Sunday through early next week.

* Adverse to dangerous surf and boating conditions are expected to
  persist through at least Sunday in response to an enhanced
  pressure gradient and a strong cold front.

* Rain chances increase inland tonight through Monday (possibly
  lingering showers Monday night into Tuesday) and again
  Wednesday night through Friday night. Greatest chances Sunday
  through Sunday night. Rain chances nearly everyday through next
  week for the Gulf Waters.

&&

.DISCUSSION...
Issued at 1113 PM CST Sat Nov 29 2025

Big changes in the weather pattern are in the offing for all of Deep
South Texas and the Rio Grande Valley. Over the next 12 or so hours,
a strong southward advancing cold front (currently moving across
central Texas) will sweep across all of Deep South Texas and the Rio
Grande Valley. Associated with this cold front will be increased
rainfall chances and blustery conditions along with falling temperatures
throughout the day on Sunday.

Due to the timing of the cold fropa, the development of blustery
north winds 10-20 mph with higher gusts and increased cloud coverage
and rain chances, high temperatures will be reached during the
morning hours with values struggling to make it out of the 70s most
places (60s across parts of the Northern Ranchlands). Rain showers
and maybe a rumble or two of thunder will increase in coverage
during the morning hours on Sunday and persist through the day.
Currently, we have low to medium (20-50%) chances along and west
of IH-69E and categorical PoPs along and east of IH-69E. Due to
the front being progressive along with cold and dry air advecting
into the region, we expect mainly rain showers (stratiform type)
on Sunday. That said, we don not anticipate the risk for flash
flooding to occur though there could be areas of ponding.

Despite cloud coverage and maybe some rain showers lingering,
additional cold and dry air advection will result in a noticeably
chilly Sunday night as overnight low temperatures are expected to
plunge into the 40s most places, some 15F degrees or so cooler
than Saturday night, and some 10F degrees cooler than normal. A
full cold and dry air advection regime will remain in place on
Monday with some lingering rain showers. This combined with a
1020-1025 mb sfc high pressure system over the region will result
in continued cooler than normal temperatures with high
temperatures struggling to make it out of the 50s on Monday and
60s on Tuesday. Clear skies and additional radiational cooling
will result in overnight low temperatures Monday and Tuesday
nights holding in the 40s most places (50s along the RGV and
immediate coast), which again will be well below normal levels.

Another bout of unsettled weather is expected to develop over the
forecast area as a nearby shortwave trough/developing low pressure
system will increase the threat for showers and thunderstorms
Wednesday night through Friday night. Currently, we have low to
medium (20-50%) chances across Deep South Texas with the higher
chances located near the coast.

Temperatures will gradually moderate through the week, however, the
combination of rain chances and increased cloud coverage will limit
warming potential. That said, high temperatures by Wednesday are
progged to reach the 70s across much of Deep South Texas. Highs
mainly in the 70s (lower 80s along the RGV) are then expected to
persist through next Sunday. Overnight lows Wednesday through
Saturday night will mainly be in the 50s. Given the explanation
above about model biases and after collaboration with neighboring
offices, have decided to use a blend of the NBM 25th percentile
and NAM12 through Tuesday.

&&

.AVIATION...
(06Z TAFS)
Issued at 1113 PM CST Sat Nov 29 2025

Key Aviation IDSS Messages for the 06z Period:

* Mainly VFR (some MVFR ceilings) through tonight.

* Rain chances increase on Sunday in response to a strong early
  season cold front with deteriorating flying conditions.

* Mainly MVFR ceilings can be expected on Sunday with IFR-LIFR
  ceilings possible from time to time, especially in the heavier
  showers.

* Southeast winds tonight will shift out of the north on Sunday
  following the cold fropa. Winds could become blustery out of the
  north through Sunday with gusts higher than 20 kts.

Through 06z Monday....Latest satellite, radar, and sfc observations
showed SCT-OVC deck of VFR-MVFR stratus to stratocumulus clouds over
the terminals with ceilings ranging between 2,500-4,000 feet AGL and
unrestricted visibilities. VCSH were seen around KBRO and KHRL.

Over the next 6-9 hours, expect for deteriorating flying
conditions to take place. Ahead of an approaching and strong cold
front, clouds are expected to increase and lower in elevation. A
nearby shortwave trough and low pressure system plus increased sfc
convergence associated with the approaching frontal boundary will
increase shower and thunderstorm chances over the terminals on
Sunday.

Have maintained Prob30 groups for the TAF sites to account for the
likelihood of rain developing Sunday morning through Sunday evening.
Any showers or storms that move over a TAF site will have the capabilities
of reducing cigs/vsbys to IFR-LIFR levels.

Southeast winds 5-10 kts tonight will shift out of the north on Sunday
in response to a cold fropa. Winds are expected to become blustery
during the day with speeds between 10-15 kts and gusts between 20-25
kts.

&&

.MARINE...
Issued at 1113 PM CST Sat Nov 29 2025

Small Craft Exercise Caution (SCEC) conditions are expected
to persist through tonight. An enhanced pressure gradient from a
strong cold front will result in strong winds and increased seas on
Sunday. These hazardous marine conditions will persist into Monday
before showing some improvements. A Small Craft Advisory has been
issued from 6 AM CST Sunday to 6 AM CST Monday as a result.
Adverse to hazardous marine conditions are expected to persist
through Tuesday before becoming more favorable thereafter.

&&

.PRELIMINARY POINT TEMPS/POPS...
BROWNSVILLE             84  71  74  49 /  10  20  70  60
HARLINGEN               85  67  71  47 /  10  10  60  50
MCALLEN                 86  68  71  49 /   0   0  30  40
RIO GRANDE CITY         87  63  66  47 /   0   0  20  40
SOUTH PADRE ISLAND      80  74  74  56 /  10  30  80  70
BAYVIEW/PORT ISABEL     83  70  74  49 /  10  30  70  60

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...Small Craft Advisory from 6 AM Sunday to 6 AM CST Monday for
     GMZ130-132-135-150-155-170-175.

&&

$$

SHORT TERM...23-Evbuoma
LONG TERM....23-Evbuoma
AVIATION...23-Evbuoma