748
FXUS64 KBRO 040506 AAA
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
1206 AM CDT Thu Sep 4 2025

...New AVIATION...

.DISCUSSION...
Issued at 1009 PM CDT Wed Sep 3 2025

HOT AND DRY CONDITIONS TO PERSIST THROUGH FRIDAY:

After scattered showers and thunderstorms peppered parts of the
local forecast area earlier this week, a reprieve (albeit brief)
from the unsettled weather will take place through Friday. With a
1010-1015 hpa sfc high pressure system over the Gulf Waters and a
591 dam heat ridge overhead, hot, humid, and mostly clear skies
will persist through Friday. Hotter than normal temperatures will
take place on Thursday and Friday with highs ranging from the
upper 90s near the Lower Texas Coast to the lower 100s most other
places (basically along and west of IH-69E).

While the ambient temperatures will be hot, drier air in place
over the region will not result in as hot heat indices as what
could be. Heat indices are expected to range between 100-110F
degrees. This will result in Heat Risk ranging between Moderate
(Level 2 of 4) to Major (Level 3 of 4) across much of Deep South
Texas Thursday and Friday.

MORE RAIN, LOCALLY HEAVY RETURNS OVER THE WEEKEND THROUGH EARLY
NEXT WEEK:

Focus then shifts on a return to more widespread rain chances this
weekend through at least the early parts of next week. Global
forecast models/ensembles continue to indicate an increase in deep
tropical moisture from the remnants of Hurricane Lorena and from the
Gulf advecting over Deep South Texas and the Rio Grande Valley
during this time period. The GFS is indicating a plume of
precipitable water (PWAT) values ranging between 2-2.5+ inches over
the local forecast area Saturday through the early parts of next
week. A weakening/stalling frontal boundary to our north over
central/southern Texas coupled with the anomalously high PWAT values
will be the impetus of day-to-day shower and thunderstorm chances
from Saturday/Saturday night through at least the early parts of
next week. Note: September is typically our wettest month of the
year!

While some of the more salient details still needs to be ironed out,
it appears that there is the potential for some appreciable and much
needed rainfall through at least the early parts of next week. The
50th percentile or most likely scenario from the NBM suggest that
anywhere from 1.50-3.00+ inches of rainfall with locally higher
amounts is possible by Wednesday morning over the region with the
highest amounts favored along and east of IH-69C.

In addition to the respectable rainfall totals during this period,
flash flooding is possible given how efficient the rainfall will
be courtesy of the heightened atmospheric moisture content and the
potential for some of the storms to be slow movers likely training
over the same areas given the weak jet stream winds/dynamics aloft
in place. This despite how antecedently dry it`s been. Given the
situation, the Weather Prediction Center (WPC) has placed the entire
area under a Marginal (Level 1 of 4) Risk for Excessive Rainfall
Sunday/Sunday night.

TEMPERATURE TREND SATURDAY THROUGH NEXT WENDESDAY:

Despite Saturday being the onset of this rain event, it is expected
to be the hottest day of the weekend and days to follow.
Depending on the precise timing of shower and thunderstorm
development, high temperatures will have the chance to climb into
the upper 90s to lower 100s. High humidity levels will result in
heat indices ranging between 105-113F degrees on Saturday (hotter
than normal levels). This will result in a continuation of
Moderate (Level 2 of 4) to Major (Level 3 of 4) Heat Risk on
Saturday.

Sunday through the middle parts of next week, the combination of
clouds and rain will help to keep the heat away. Anomalies are
expected to run normal to slightly cooler than normal levels for
early September standards. High temperatures during this time period
will range in the lower to mid 90s.

&&

.AVIATION...
(06Z TAFS)
Issued at 1201 AM CDT Thu Sep 4 2025

VFR will prevail at the aerodromes through the next 24 hours.
Light to moderate winds with breezy daytime gusts and clear
skies are anticipated.

&&

.MARINE...
Issued at 1009 PM CDT Wed Sep 3 2025

Favorable marine conditions will continue with low to moderate seas
and light winds through Friday. The threat for showers and
thunderstorms increase over the weekend through at least the early
parts of next week as moisture increases and a cold frontal boundary
stalls to the north.

&&

.PRELIMINARY POINT TEMPS/POPS...
BROWNSVILLE             98  78  96  80 /   0   0  20  30
HARLINGEN              100  74  99  75 /   0   0  10  10
MCALLEN                103  78 102  80 /   0   0  10   0
RIO GRANDE CITY        104  76 103  77 /   0   0   0   0
SOUTH PADRE ISLAND      90  82  89  83 /   0   0  20  50
BAYVIEW/PORT ISABEL     95  77  94  78 /   0   0  10  30

&&

.BRO WATCHES/WARNINGS/ADVISORIES...None.

&&

$$