Armstrong, Texas Weather Forecast Discussion

952
FXUS64 KBRO 210344
AFDBRO
Area Forecast Discussion
National Weather Service Brownsville TX
1044 PM CDT Sat Sep 20 2025
...New DISCUSSION, MARINE...
.KEY MESSAGES...
Updated at 1043 PM CDT Sat Sep 20 2025
- Unsettled weather continues most days of the forecast with
   showers and thunderstorms developing along seabreeze boundaries
   during the daytime. Lightning, heavy rain and some gusty winds
   are possible, with the best chances generally closer to the
   immediate coastline.
- Afternoon high temperatures increase to above average Monday through
   Wednesday, especially further inland, with moderate to major
   (levels 2 and 3 out of 4) heat risks likely. SPS`s for heat may
   be possible as afternoon heat indices are expected to climb to
   near, or surpass, 108 degrees F for a few hours in some inland
   locations Monday through Wednesday.
- Forecast confidence is low to medium from the middle part of
   this upcoming week and beyond.
&&
.DISCUSSION...
Issued at 1043 PM CDT Sat Sep 20 2025
The focus of the forecast for the next 7 days across Deep South
Texas and the Rio Grande Valley will be a mix of increasing heat
risks into the middle of this upcoming week as well as unsettled
weather. Slight shortwave troughing along the eastern periphery of a
mid-level high over northwestern Mexico is likely to result in a low
to medium (20-50%) chance of rain today from convection, mostly east
of Zapata County. As is the ongoing diurnal pattern throughout the
forecast, convection is likely to develop along the seabreeze
boundary by mid-day in the coastal areas, spreading westward into
the afternoon and early evening hours, bringing the possibility of
lightning, heavy rain and localized gusty winds, maximizing in
coverage east of US-281 with probabilities highest along the coast
before activity ceases beyond sunset. Overnight tonight and through
Monday, mid-level ridging increases subsidence over the CWA as the
mid-level high expands and shifts eastward to central-northern
Mexico, decreasing PoP`s to a low (15-30%) chance east of US-281 on
Monday and Tuesday. Meanwhile, an enhanced upper level jet over the
Rockies induces a cold front arriving into southern-central Texas on
Wednesday, increasing PoP`s across the entire region to a low to
medium (30-60%) chance into Thursday as the front may stall across
the CWA. If the front reaches our region, a wind shift out of the
east-northeast is possible on Thursday and Friday. Following, mid-
level ridging behind a departing trough over the eastern CONUS
decreases PoP`s from a low to medium (30-40%) chance on Friday to a
low (20-30%) chance over the weekend.
Afternoon high temperatures increase from near to slightly above
average temperatures today to as much as 5-7 degrees F above average
further inland, perhaps even warmer, tomorrow through Wednesday as
highs peak into the mid/upper 90s across all of inland Deep South
Texas, even surpassing 100 degrees F for portions of the Rio Grande
Plains as well as the mid and upper Rio Grande Valley. This will
increase heat risks from minor to moderate (levels 1 and 2 of 4)
today to mostly moderate (level 3 of 4) tomorrow, with pockets of
moderate expanding in coverage across the Rio Grande Valley and the
Rio Grande Plains by Tuesday and Wednesday. Increased cloud coverage
Thursday and drier air infiltrating the region over the weekend is
currently expected to result in a range of minor to moderate on
Thursday to mostly minor over the weekend. SPS`s may be possible
Monday through Wednesday due to afternoon heat indices reaching 108
degrees F, or warmer, for a few hours in the afternoon.
The forecast described above reflects the latest blend of models.
However, it should be noted that the probabilities of rain are
subject to change, particularly by the middle and later part of the
week. The ensemble runs of the 18Z GFS and ECMWF indicate
probabilities of rain not increasing until Wednesday evening,
according to the ECMWF, which has a more aggressive southward push
of the front through the region on Thursday, with PoP`s mostly
diminished by Friday afternoon, whereas the GFS stalls the front
across the CWA on Friday with increased PoP`s Thursday into
Saturday. Therefore, confidence in resulting temperatures is low,
medium at best, for Wednesday onward, but confidence is likely to
increase over the next few days.
&&
.AVIATION...
(00Z TAFS)
Issued at 617 PM CDT Sat Sep 20 2025
Although the bulk of heavy rain is west/northwest at this time, a
few pop up showers, or brief thunderstorm, at or near KMFE is
possible in the next 1-2 hours before convective activity ceases
through the early nighttime hours at all terminals. PROB30`s have
been introduced for KBRO late tonight/early tomorrow morning for
the possibility of a shower or thunderstorm and as well as
PROB30`s are forecast for all TAF sites during the afternoon and
early evening hours on Sunday as convection develops along the
seabreeze boundary. Gentle easterly winds become light and/or
variable tonight before picking back up out of the southeast tomorrow
afternoon. Outside of convection, VFR conditions prevail.
&&
.MARINE...
Issued at 1043 PM CDT Sat Sep 20 2025
Slight to moderate (2-3 ft) seas prevail into next week as a result
of gentle to moderate southeasterly-southerly winds, becoming
variable by Thursday. Chances of showers and thunderstorms
continue.
&&
.PRELIMINARY POINT TEMPS/POPS...
BROWNSVILLE             78  92  78  93 /  20  50  10  20
HARLINGEN               74  93  74  95 /  20  50  10  20
MCALLEN                 77  96  78  98 /  10  30  10  10
RIO GRANDE CITY         74  97  75  99 /  10  20   0  10
SOUTH PADRE ISLAND      82  88  82  89 /  30  50  20  30
BAYVIEW/PORT ISABEL     77  90  77  92 /  30  50  20  20
&&
.BRO WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...None.
&&
$$
SHORT TERM...65-Irish
LONG TERM....65-Irish
AVIATION...65-Irish

NWS BRO Office Area Forecast Discussion