textproduct: Brownsville/Rio Grande Valley

KEY MESSAGES

Updated at 301 PM CDT Mon Oct 5 2026

- The National Hurricane Center (NHC) indicates a medium (40%) of tropical development of a low pressure system, currently situated over the southwestern Gulf, through the next 48 hours and a high (80%) chance of tropical development through the 7 day forecast.

- The greatest impacts are likely to be an ongoing coastal flooding and rip current threat, though additional heavy rain is possible from the strengthening system over the Gulf.

- The Weather Prediction Center (WPC) continues a Marginal Risk of isolated flash flooding from excessive and heavy rainfall along/east US-281 through Thursday.

- Temperatures warm from slightly below average today to near average by tomorrow, while mostly minor risks of heat-related illnesses (level 1/4) persist.

DISCUSSION

Issued at 301 PM CDT Mon Oct 5 2026

Well-above average moisture content from a departing frontal boundary and modest upper level divergence from a deepening trough over the southwestern Gulf maintain medium to likely (40-90%) chances of rain through Wednesday, remaining mostly along/east I-69 E. Towards the middle to later part of the week, slightly better forcing and a bit of vorticity advection from a shortwave passing over Texas could bring a region-wide medium to likely (40-70%) chance of rain on Thursday and a low to medium (20-40%) on Friday. Following, low (15-30%) chances of rain still remain possible along/east US-281.

In association with the deepening trough over the Gulf, NHC indicates a medium (40%) of tropical development of a low pressure system, currently situated over the southwestern Gulf, through the next 48 hours and a high (80%) chance of tropical development through the 7 day forecast. Although the greatest concern from this system is likely to remain an ongoing coastal flooding and rip current threat, associated surface troughing could work with daytime instability and well-above average moisture content to lead to additional heavy showers and a few thunderstorms through Thursday, discussed further below.

At this time, there is the possibility of total additional rainfall amounts by Friday morning ranging around 1.0-4.5 inches, or more, along/east I-69 E, highest over the Gulf Coast; LREF probabilistic data suggests a 30-60% probability of totals exceeding 3 inches across the eastern portions of the Lower RGV, highest along the coast, where there is a 30-40% probability of exceeding 4 inches. Due to this risk, WPC gradually expands a Marginal Risk of isolated flash flooding from southeast Cameron today/tonight to all of the Lower RGV to as far north as southern Kenedy and as far west as southeastern Hidalgo County on Wednesday, sliding eastward to the easternmost counties on Thursday. However, it should be noted that there remains a great deal of uncertainty with this forecast, especially with how the shortwave passing over the Southern Plains interacts with the potential developing tropical system, so the flooding risk and expected rainfall amounts are highly subject to change.

Otherwise, partial cloud clearing is expected to warm high temperatures from the low/mid 80s today to the upper 80s/low 90s by tomorrow. Return flow and increasing moisture content over the weekend could warm temperatures further to the low/mid 90s while also expanding moderate risks of heat-related illnesses from the populated regions of the RGV to more of deep south Texas by the beginning of next week. Minor heat risks are expected for most of the CWA in the meantime.

AVIATION

(18Z TAFS) Issued at 1214 PM CDT Mon Oct 5 2026

Overcast MVFR skies are likely to continue through the 18Z TAF cycle, especially at KHRL and KBRO, though some drier air arriving further west tonight may allow for ceilings to rise to VFR over KMFE this evening and possibly scattered overnight. Yet, in the meantime, intermittent light to moderate shower activity could result in brief periods of IFR ceilings at all TAF sites. Moderate northerly winds (10-15+ knots, gusting to 20-25 knots) become light to gentle overnight. Drier conditions are anticipated by tomorrow morning as northwesterly winds further east (KHRL and KBRO) pick back up to similar speeds as today, though remaining light at KMFE.

MARINE

Issued at 301 PM CDT Mon Oct 5 2026

Seas are expected to continue improving throughout the remainder of this evening and overnight as northerly to northeasterly winds gradually weaken to moderate to fresh, with moderate (3-5 ft) seas prevailing through the middle of the week. The rest of the forecast is subject to change and will largely be dependent on the strengthening of a low pressure system over the southwestern Gulf, which NHC has a medium (40%) of tropical development through the next 48 hours and a high (80%) chance of tropical development through the 7 day forecast. For the time being, medium to likely (50- 90%) chances of rain gradually drop throughout the weekend to a low to medium (20-40%) chance.

PRELIMINARY POINT TEMPS/POPS

BROWNSVILLE 75 87 76 89 / 80 80 50 70 HARLINGEN 71 89 72 92 / 70 60 30 60 MCALLEN 74 92 75 94 / 20 20 10 40 RIO GRANDE CITY 72 92 72 93 / 10 0 0 10 SOUTH PADRE ISLAND 79 85 80 86 / 90 80 70 80 BAYVIEW/PORT ISABEL 75 87 76 89 / 90 80 60 70

BRO WATCHES/WARNINGS/ADVISORIES

TX...High Rip Current Risk until 7 PM CDT this evening for TXZ451-454- 455.

GM...Small Craft Advisory until 7 PM CDT this evening for GMZ135-155- 175.