709
FXUS64 KBRO 181719
AFDBRO

Area Forecast Discussion
National Weather Service Brownsville TX
1219 PM CDT Fri Sep 18 2026

...New DISCUSSION, AVIATION, MARINE...

.KEY MESSAGES...
Updated at 1210 PM CDT Fri Sep 18 2026

- There is Moderate (level 2 of 4) Heat Risk this afternoon. Heat
  indices could climb over 108 across the Rio Grande Valley and
  Coastal Counties for an hour or two this afternoon.

- Low to moderate (20 to 50%) chance of showers and thunderstorms
  continue across Deep South Texas this afternoon, before
  conditions dry out tomorrow for the weekend.

- Rain chances return early next week and continue throughout the
  week. Heat Risk will continue as well.

- There is a moderate risk of rip currents at area beaches.

&&

.DISCUSSION...
Issued at 1210 PM CDT Fri Sep 18 2026

An unsettled weather pattern continues over the next few days as an
area of strong high pressure over the Southeastern CONUS continues
to backbuild westward, with northeasterly upper level flow beneath
the underside of of this high reaching Deep South Texas.  Because
this northeasterly airmass has spend considerable time over the
Gulf, the atmospheric profile is expected to remain considerably
moist this afternoon, with PWATs over 2 inches. This will support
low to moderate (20 to 50%) rain chances this afternoon. The rain is
expected to be overall beneficial, with most areas receiving no more
than half an inch.  However, some heavier showers and thunderstorms
could cause locally heavier amounts with the potential for nuisance
ponding.

As high pressure continues to build westward over northeastern Texas
though the weekend, upper-level subsidence will keep conditions dry
for the weekend. A shower or two cannot be completely ruled out
along the sea breeze, but rain chances remain very low for both
Saturday and Sunday.

Rain chances are expected to pick up again next week as more moist
air is advected into the region as northeasterly flow continues.
Sea breeze activity is possible each day next week. However,
longer-range guidance is not in agreement as to whether the upper
level ridge over northeast Texas is going to continue through
next week, or begin to break down as a trough approaches from the
west. While the current NBM guidance is supporting low to moderate
(20 to 40%) PoPs starting Tuesday, this could trend higher or
lower depending on the behavior of the high pressure system and
the trough to our west. Chances could decrease if the high
pressure stays stronger over Texas, but we could see an increase
in widespread rain chances if the approaching trough is able to
break down the ridge and produce any shortwave disturbances as it
approaches.

Heat Risk will remain a concern over the next week. Though
increased cloud cover and rain chances may bring some small
temperature relief by a few degrees, the humid airmass will
continue to keep heat indices high. Heat indices will be elevated
today, with some areas exceeding 108 degrees for an hour or two
this afternoon. We will likely see more elevated heat indices this
weekend as well.

There is a moderate risk of rip currents at area beaches today.

&&

.AVIATION...
(18Z TAFS)
Issued at 1210 PM CDT Fri Sep 18 2026

VFR conditions are expected at all airports, but a TEMPO has been
added for showers and thunderstorms, as we are presently seeing scattered
convective activity develop throughout Deep South Texas. If a
shower or thunderstorm happens to occur near the airport, it could
temporarily deteriorate conditons. Otherwise, light to moderate
northeasterly winds are expected with few clouds.

&&

.MARINE...
Issued at 1210 PM CDT Fri Sep 18 2026

Favorable conditions are expected over the next several days with
light to moderate northeasterly winds and low to moderate (2-4 feet)
wave heights.  Offshore showers and thunderstorms are possible
throughout next week, which could temporarily deteriorate
conditions in their immediate vicinity.

&&

.PRELIMINARY POINT TEMPS/POPS...
BROWNSVILLE             95  79  95  78 /  30   0  10   0
HARLINGEN               97  75  98  74 /  30   0  10   0
MCALLEN                 99  78 100  78 /  50   0  10   0
RIO GRANDE CITY         99  77 101  77 /  40  10   0   0
SOUTH PADRE ISLAND      89  81  89  81 /  30  20  20   0
BAYVIEW/PORT ISABEL     94  78  94  77 /  30  10  10   0

&&

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

$$

SHORT TERM...55-MM
LONG TERM....55-MM
AVIATION...55-MM