textproduct: Brownsville/Rio Grande Valley

KEY MESSAGES

Updated at 515 AM CST Sun Nov 30 2025

* Big changes to the weather pattern in store as a strong cold front tonight into Sunday will bring a notably cooler airmass (potentially the coldest since last February) to the region Sunday through early next week.

* Adverse to dangerous surf and boating conditions are expected to persist through at least Sunday in response to an enhanced pressure gradient and a strong cold front.

* Rain chances increase inland tonight through Monday (possibly lingering showers Monday night into Tuesday) and again Wednesday night through Friday night. Greatest chances Sunday through Sunday night. Rain chances nearly everyday through next week for the Gulf Waters.

DISCUSSION

Issued at 1113 PM CST Sat Nov 29 2025

Big changes in the weather pattern are in the offing for all of Deep South Texas and the Rio Grande Valley. Over the next 12 or so hours, a strong southward advancing cold front (currently moving across central Texas) will sweep across all of Deep South Texas and the Rio Grande Valley. Associated with this cold front will be increased rainfall chances and blustery conditions along with falling temperatures throughout the day on Sunday.

Due to the timing of the cold fropa, the development of blustery north winds 10-20 mph with higher gusts and increased cloud coverage and rain chances, high temperatures will be reached during the morning hours with values struggling to make it out of the 70s most places (60s across parts of the Northern Ranchlands). Rain showers and maybe a rumble or two of thunder will increase in coverage during the morning hours on Sunday and persist through the day. Currently, we have low to medium (20-50%) chances along and west of IH-69E and categorical PoPs along and east of IH-69E. Due to the front being progressive along with cold and dry air advecting into the region, we expect mainly rain showers (stratiform type) on Sunday. That said, we don not anticipate the risk for flash flooding to occur though there could be areas of ponding.

Despite cloud coverage and maybe some rain showers lingering, additional cold and dry air advection will result in a noticeably chilly Sunday night as overnight low temperatures are expected to plunge into the 40s most places, some 15F degrees or so cooler than Saturday night, and some 10F degrees cooler than normal. A full cold and dry air advection regime will remain in place on Monday with some lingering rain showers. This combined with a 1020-1025 mb sfc high pressure system over the region will result in continued cooler than normal temperatures with high temperatures struggling to make it out of the 50s on Monday and 60s on Tuesday. Clear skies and additional radiational cooling will result in overnight low temperatures Monday and Tuesday nights holding in the 40s most places (50s along the RGV and immediate coast), which again will be well below normal levels.

Another bout of unsettled weather is expected to develop over the forecast area as a nearby shortwave trough/developing low pressure system will increase the threat for showers and thunderstorms Wednesday night through Friday night. Currently, we have low to medium (20-50%) chances across Deep South Texas with the higher chances located near the coast.

Temperatures will gradually moderate through the week, however, the combination of rain chances and increased cloud coverage will limit warming potential. That said, high temperatures by Wednesday are progged to reach the 70s across much of Deep South Texas. Highs mainly in the 70s (lower 80s along the RGV) are then expected to persist through next Sunday. Overnight lows Wednesday through Saturday night will mainly be in the 50s. Given the explanation above about model biases and after collaboration with neighboring offices, have decided to use a blend of the NBM 25th percentile and NAM12 through Tuesday.

AVIATION

(12Z TAFS) Issued at 515 AM CST Sun Nov 30 2025

The majority of the TAF period will see a mixture of MVFR to IFR conditions as a cold front moves through the region bringing some showers and thunderstorms to the region. The timing for the showers have been based around the HRRR. Some gusty northerly winds behind the front with those gusts around 20 to 25 knots.

MARINE

Issued at 1113 PM CST Sat Nov 29 2025

Small Craft Exercise Caution (SCEC) conditions are expected to persist through tonight. An enhanced pressure gradient from a strong cold front will result in strong winds and increased seas on Sunday. These hazardous marine conditions will persist into Monday before showing some improvements. A Small Craft Advisory has been issued from 6 AM CST Sunday to 6 AM CST Monday as a result. Adverse to hazardous marine conditions are expected to persist through Tuesday before becoming more favorable thereafter.

PRELIMINARY POINT TEMPS/POPS

BROWNSVILLE 74 49 58 54 / 70 60 40 30 HARLINGEN 71 47 56 49 / 60 50 30 20 MCALLEN 71 49 58 52 / 30 40 20 20 RIO GRANDE CITY 66 47 60 50 / 20 40 20 10 SOUTH PADRE ISLAND 74 56 63 62 / 80 70 50 40 BAYVIEW/PORT ISABEL 74 49 59 53 / 70 60 40 30

BRO WATCHES/WARNINGS/ADVISORIES

TX...High Rip Current Risk through Monday afternoon for TXZ451-454- 455.

GM...Small Craft Advisory until 6 AM CST Monday for GMZ130-132-135- 150-155-170-175.