textproduct: Brownsville/Rio Grande Valley

KEY MESSAGES

Updated at 508 AM CST Fri Dec 12 2025

* Fog, mist, low stratus possible tonight. * Warmer than normal temperatures and mainly rain-free weather will prevail through next week. * Our next best chance for rain will be on Sunday in response to a cold front; medium (40-60%) chances on Sunday.

* Hazardous marine and coastal conditions are expected to develop on Sunday and persist through Monday in response to the cold front.

DISCUSSION

Issued at 1027 PM CST Thu Dec 11 2025

The forecast period of Deep South Texas and the Rio Grande Valley is expected to be mainly rain-free with maybe a couple of chances for rain and warmer than normal temperatures.

Through tonight, the main weather concern will be the potential for some fog/mist/low stratus to develop. Current observations show clear skies over the region fostering strong radiational cooling. Dewpoint depressions were seen ranging between 0F to 3F degrees. The HREF model is indicating a general medium (40-60%) chance/risk for fog developing across much of Deep South Texas and the Rio Grande Valley tonight. Not confident at this time to issue a Dense Fog Advisory and will need to monitor trends through the night for that. That said, there is enough confidence to insert the potential for some mist/fog/low stratus developing tonight. Otherwise, expect for a quiet night under mostly clear skies and milder than normal temperatures.

As highlighted earlier, much of the forecast period will be dry/rain- free. That said, Sunday will feature our next best and widespread chance for showers to develop. A strong southward advancing cold front, associated with an Arctic 1040-1045 mb sfc high pressure system that will be centered over the Midwest, will approach the region. As this happens, the combination of increased sfc convergence and a nearby weak shortwave trough will increase the prospects for showers (maybe an isolated thunder) to develop over the region on Sunday. Currently, we have a medium (40-60%) chance for showers across Deep South Texas on Sunday. Rain chances diminish from north to south as the cold front sweeps through the region and shifts into northeastern Mexico.

Up, down, up (roller-coaster) temperature pattern will take place through the forecast period or through next Friday, thanks to the cold front that will sweep through the region on Sunday. Overall, temperatures will average out warmer than normal for the balance of the forecast period with daytime highs in the 80s each day except for Sunday through Tuesday. Ahead of the cold front on Sunday, high temperatures will top out in the 70s most places (lower 80s along parts of the RGV). Monday is progged to be the coolest day of the forecast period with daytime highs in the 60s most places (70s along the RGV). Finally, on Tuesday, temperatures will begin to moderate as daytime highs are expected to climb back into the 70s most places. Overnight low temperatures will mainly be in the 50s and 60s during the forecast period.

AVIATION

(12Z TAFS) Issued at 508 AM CST Fri Dec 12 2025

While generally VFR conditions are expected for most of the TAF cycle, the next couple of hours could see conditions range from MVFR to LIFR due some shallow ground fog or low-level clouds over the region. By the mid-morning the low-level clouds and fog should out of the region allowing for VFR conditions to persist along with some breezy southerly winds with gusts up to 20 knots. The winds are expected to weaken by late this evening.

MARINE

Issued at 1027 PM CST Thu Dec 11 2025

Favorable marine conditions with low to moderate winds and seas will persist through Saturday night. On Sunday, marine conditions deteriorate with Small Craft Exercise Caution (SCEC) to Small Craft Advisory (SCA) conditions developing in response the aforementioned cold front. These conditions will persist through Monday/Monday evening before showing some improvements with mainly moderate seas.

PRELIMINARY POINT TEMPS/POPS

BROWNSVILLE 82 68 82 67 / 0 30 30 10 HARLINGEN 83 64 83 62 / 0 20 20 10 MCALLEN 85 67 86 66 / 0 10 10 10 RIO GRANDE CITY 84 63 83 63 / 0 0 0 0 SOUTH PADRE ISLAND 76 69 76 69 / 0 30 40 20 BAYVIEW/PORT ISABEL 80 65 80 64 / 0 30 30 10

BRO WATCHES/WARNINGS/ADVISORIES

TX...None. GM...None.