218 FXUS64 KBRO 231725 AFDBROArea Forecast Discussion National Weather Service Brownsville TX 1225 PM CDT Tue Sep 23 2025
...New DISCUSSION, AVIATION, MARINE...
.DISCUSSION... Issued at 1217 PM CDT Tue Sep 23 2025
The main focus for the forecast continues to be the unsettled weather over Deep South Texas and the Rio Grande Valley. While PWAT values continue to remain around 2 inches indicating that the environment continues to be moist and favorable for the development of showers and thunderstorms. While the rain chances are generally in the range low to medium (20 to 50%), the chances for rain during the day tomorrow are still uncertain at this point. While the models have very high chances for rain, those chances are very dependent on what happens with a frontal boundary that could come through the region, stall out over the area, or even remain to the north as well. Because there continues to remain so much uncertainty with this part of the forecast, PoPs have been lowered from the NBM. At this point, medium (40-70%) chances for rain are expected for Thursday, however this is likely to change depending on what occurs with the front. The last several model trends have the frontal boundary stall towards the north of the region, but there is still a chance that the frontal boundary could move further south sometime late Thursday into early Friday. Will need to continue to monitor the model trends to see how this frontal boundary evolves. The Storm Prediction Center does have Deep South Texas and the Rio Grande Valley in a marginal risk (level 1 of 4) for tomorrow.
As for the temperatures for the forecast period. Highs are typically in the 90s for the region with a few places in Western Starr and Zapata reaching into the triple digits. The area is generally in a moderate (level 2 of 4) for Heat Risk, however today and Wednesday parts of the region do go into major (level 3 of 4) for Heat Risk. While the heat indices do remain below the criteria for Heat Advisory, an SPS for elevated heat indices could be issued for parts of the area.
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.AVIATION... (18Z TAFS) Issued at 1217 PM CDT Tue Sep 23 2025
Generally VFR conditions are expected to persist through the TAF cycle at all TAF sites. Southeasterly winds are expected to continue with some gusts around 20 knots are also possible. Low- level clouds will continue to move through the region due to the low-level moisture flow. While some showers and thunderstorms are possible during the afternoon hours, confidence was not high enough to include them in the TAF package.
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.MARINE... Issued at 1217 PM CDT Tue Sep 23 2025
Marine conditons are generally expected to be favorable with mostly light to moderate southeasterly winds and low seas around 2 to 3 feet. While showers and thunderstorms chances are expected to be generally low to moderate (20 to 50%) for the forecast period. There is a greater chance for more showers and thunderstorms on Thursday depending on what occurs with a frontal boundary that could move through the Lower Texas coast on Thursday.
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.PRELIMINARY POINT TEMPS/POPS... BROWNSVILLE 80 94 78 91 / 10 30 30 70 HARLINGEN 77 96 76 92 / 0 30 30 70 MCALLEN 80 99 79 95 / 0 20 30 60 RIO GRANDE CITY 77 101 76 93 / 0 20 40 60 SOUTH PADRE ISLAND 83 89 81 88 / 20 30 50 70 BAYVIEW/PORT ISABEL 79 92 77 89 / 10 30 40 70
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.BRO WATCHES/WARNINGS/ADVISORIES... TX...None. GM...None. &&
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SHORT TERM...64-Katz LONG TERM....64-Katz AVIATION...64-Katz
NWS BRO Office Area Forecast Discussion