619
FXUS64 KBRO 011121 AAB
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
621 AM CDT Mon Sep 1 2025

...New AVIATION...

.KEY MESSAGES...
Updated at 614 AM CDT Mon Sep 1 2025

-Heat continues to be a concern on Monday with a Moderate (level 2
out of 4) to Major (level 3 out of 4 )Heat risk.

-Rain chances increase on Monday and Tuesday.

-The Weather Prediction Center continues to highlight portions of
 Starr, Zapata, Jim Hogg, Brooks, and Kenedy counties in a
 Marginal Risk (level 1 of 4) of excessive rainfall on Monday.

&&

.DISCUSSION...
Issued at 1016 PM CDT Sun Aug 31 2025

Heat continues to be the a concern for the start of the forecast
period. Mid-level ridging and moisture advection with south-
southeasterly winds will continue to bring hot temperatures rising
into the upper 90s to 100s and heat indices between 105 to 110
degrees across Deep South Texas and the Rio Grande Valley on
Monday. This will maintain a moderate (level 2 out of 4) to Major
(level 3 out of 4) Heat risk for the region. While heat indices
will remain below Heat Advisory criteria, Special Weather
Statements will be needed. With that said, a cold front begins to
push southward into the CWA on Monday. This will bring increasing
chances of showers and thunderstorms on Monday (40-50%). Rainfall
and cloud cover associated with the cold front could limit
afternoon high temperatures, heat indices, and heat risk.

WPC has portions of the Northern Ranchlands in a marginal risk
(level 1 of 4) of excessive rainfall for Monday into Monday night.
The NBM 90th percentile is at around 1 to 1.5 inches and mean
around 0.5 inch of rainfall for the marginal area, so confidence
on the excessive rainfall is somewhat low. With the said,
forecasted PWATs will be around 1.75 inches, which is above normal
so any showers or thunderstorms that do develop will be capable
of producing heavy rainfall that could lead to ponding of water,
especially on roadways and low lying areas.

The aforementioned cold front will move through the CWA Monday
night, but lift back north across Deep South Texas on Tuesday. This
will keep rain chances (50-70%) in the forecast for Tuesday.
Temperatures cool slightly, but will remain near to just above
seasonal norms through Thursday.

Rain chances taper off Tuesday night and the front finally pushes
south of the region. POPs will generally remain around 15% or less
for Wednesday through Friday. As we head into next weekend, we are
still watching for the potential of another front pushing through or
stalling across Deep South Texas that will increase rain chances and
lower temperatures slightly for the weekend.

&&

.AVIATION...
(12Z TAFS)
Issued at 614 AM CDT Mon Sep 1 2025

Some isolated showers and thunderstorms will be possible this
afternoon as a weak frontal boundary moves south through the
region. While VFR conditions are expected to prevail through most
of the period, brief reductions to MVFR or IFR ceilings and
visibilities could occur with any convection that develops.

Light southeasterly winds this morning are expected to become
easterly this afternoon as the frontal boundary moves through the
area, with wind speeds likely remaining around 10kts.

&&

.MARINE...
Issued at 1016 PM CDT Sun Aug 31 2025

Generally favorable conditions with mostly light to moderate
southerly to southeasterly winds and seas of 1 to 2 feet. A frontal
boundary will move through the waters off the lower Texas coast on
Monday increasing rain and thunderstorm chances Monday and
Tuesday (50-70%). This could lead to locally elevated winds and
seas.

&&

.PRELIMINARY POINT TEMPS/POPS...
BROWNSVILLE             94  79  95  78 /  30  30  60  30
HARLINGEN               97  75  95  73 /  40  40  60  10
MCALLEN                101  79  98  77 /  30  40  60  20
RIO GRANDE CITY        101  77  97  75 /  20  60  50  20
SOUTH PADRE ISLAND      89  81  89  81 /  30  40  50  20
BAYVIEW/PORT ISABEL     93  77  93  77 /  30  40  60  20

&&

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

$$

SHORT TERM...68
LONG TERM....68
AVIATION...60-BE