256
FXUS64 KBRO 180344
AFDBRO

Area Forecast Discussion
National Weather Service Brownsville TX
1044 PM CDT Thu Sep 17 2026

...New DISCUSSION, MARINE...

.KEY MESSAGES...
Updated at 1028 PM CDT Thu Sep 17 2026

 - Low (15-30%) chances of rain near the coast tonight spread
   further inland and increase to a low to medium (20-40%) chance
   along/west US-281 by Friday afternoon before diminishing
   throughout Friday evening.

 - Rain chances minimize Friday night into Saturday before
   gradually increasing and expanding on Sunday to region-wide
   low to medium chances by possibly next Tuesday.

 - Mainly moderate risks of heat-related illnesses (level 2/4) on
   Friday and Saturday re-escalate to moderate to major (level
   3/4) risks by Sunday.

 - A moderate risk of life-threatening rip currents continues
   through Friday afternoon.

&&

.DISCUSSION...
Issued at 1028 PM CDT Thu Sep 17 2026

Low (15-30%) chances of passing showers along/east I-69 E tonight
spread further inland along the seabreeze boundary on Friday,
increasing to a low to medium (20-40%) chance along/west US-281 by
Friday afternoon as easterly to northeasterly winds flowing about a
surface high pressure settling over the Deep South continue to push
the back half of a deep Gulf moisture plume westward. Due to above
average moisture content anticipated to linger through Friday
afternoon, moderate to heavy rain within passing convection is still
possible which could lead to brief periods of reduced visibility,
slippery roads and nuisance ponding. Additionally, a SPS for heat
indices of 108-111 F is possible on Friday for the coastal and
inland portions of Cameron, Willacy and Kenedy counties during the
afternoon and early evening hours, dependent on cloud coverage,
convective development and model trends.

Otherwise, mid- and lower-level moisture is anticipated to dry
considerably throughout the remainder of Friday night to near or
below average by Saturday morning as a result of sinking air
associated with a high pressure aloft centering over the Southern
Plains, thus cutting down on rain chances to a less than 10% chance
on Saturday and a low (15-20%) across the southern portions of the
lower and mid RGV on Sunday. Decreasing cloud cover over the
weekend is expected to slightly raise temperatures and expand
highs in the lower 100s over the Rio Grande Plains (upper 90s
elsewhere) on Friday to most areas along/west I-69 E by Sunday and
Monday; mainly moderate risks of heat-related illnesses on Friday
and Saturday deteriorate to mostly major by Monday.

Subsidence begins to wane and moisture profiles steadily moisten
throughout next week as the high pressure over the Southern Plains
becomes wedged between a stationary upper level low over the
eastern Gulf and a series of mid/upper level shortwave troughs
translating eastward across the Plains. We currently anticipate
for low (15-30%) chances of rain along/east US-281 on Monday to
expand and build to region-wide low to medium (30-40% or greater)
chances by possibly Tuesday, which could also cause temperatures
to cool slightly and improve heat risks to mainly moderate by late
week. Additional SPSs remain possible.


&&

.AVIATION...
(00Z TAFS)
Issued at 606 PM CDT Thu Sep 17 2026

Gentle to moderate east-northeasterly winds this evening become
light and/or variable overnight tonight before returning tomorrow
afternoon. A brief period of light rain or two is possible
overnight at KHRL and KBRO, with the best chances tomorrow
morning before spreading east to KMFE tomorrow afternoon. Brief
light to moderate, perhaps isolated heavy, passing showers may
intermittently reduce visibility, leading to possible short
periods of MVFR as noted in the PROB30s.

&&

.MARINE...
Issued at 1028 PM CDT Thu Sep 17 2026

Gentle to moderate northeasterly to easterly winds and moderate (3-5
ft) seas continue, becoming easterly to southeasterly winds with
slight to moderate (1-3 ft) seas later this weekend. Meanwhile, low
to medium chances of rain continue through Friday afternoon before
minimizing to low chances into the remainder of this weekend. Low
to medium chances of rain return early next week, gradually
increasing to a medium chance as the week progresses.

&&

.PRELIMINARY POINT TEMPS/POPS...
BROWNSVILLE             79  95  78  95 /  20  20  10  20
HARLINGEN               76  97  74  98 /  30  20  10  10
MCALLEN                 79  98  77  99 /  10  30  10  10
RIO GRANDE CITY         78  98  75 100 /  30  20  10   0
SOUTH PADRE ISLAND      81  88  81  88 /  30  30  20  10
BAYVIEW/PORT ISABEL     78  94  77  94 /  30  30  10  10

&&

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

$$

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