textproduct: Brownsville/Rio Grande Valley

KEY MESSAGES

Updated at 1138 AM CST Sat Nov 29 2025

* A strong cold front is expected overnight, which will bring the coldest air we have experienced since last winter, and an increased chance of rain tonight through Monday, with the best chances being tomorrow and tomorrow night.

* 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.

* Temperatures should gradually begin warming to seasonal levels again starting midweek, but another shortwave could bring more rain chances Thursday.

DISCUSSION

Issued at 1138 AM CST Sat Nov 29 2025

An approaching Arctic shortwave is expected to usher in a pattern change and bring a strong cold front to our area overnight. This is expected to be the strongest cold front of the season thus far, bringing some of the coldest air to the region since last winter. Model guidance is inconsistent as to how cold the temperatures will get. The NAM (which tends to handle stronger cold fronts more accurately for Deep South Texas) is more robust than the longer ranged Euro and GFS, proposing a temperature drop of around 10 degrees colder than what the Euro/GFS is proposing. Shorter range CAMs (such as the HRRR) are also trending cooler, closer to the NAM. For this reason, more weight was given to the NAM in blending it with NBM guidance for forecasting the temperatures tomorrow through Tuesday.

Tomorrow's high temperatures are likely to occur earlier in the day, possibly even before sunrise, and be in the upper 60s for the Northern Ranchlands and the mid-70s for the Rio Grande Valley. Post- frontal northerly winds will continue to funnel cooler air into the region throughout the day and gradually drop temperatures into the upper 40s/lower 50s by tomorrow night. This low temperature range is expected to continue to persist through Tuesday night, before a warming trend begins to take hold.

High temperatures will be coolest on Monday, getting into the upper 50s for most of Deep South Texas as cloud cover is expected to limit daytime heating. Gradual clearing should allow Tuesday's highs to warm into the 60s, and Wednesday's highs will continue warming into the 70s, with temperatures holding steady at seasonal levels in the 70s through the end of the week.

The frontal passage will also bring an increased chance of rain to the area. There could a non-severe thunderstorm or two just ahead of the front, but precip is expected to transition to stratiform rain and drizzle following the frontal passage. Rain chances should start increasing tonight, with a low (20-30%) chance of showers mainly for the coastal counties this evening overnight. This will become more widespread tomorrow with a low to medium (20-50%) chance expanding west of I-69C, with higher chances (50-80%) further east. The best chance for rain in the Western counties will be Sunday night into Monday, when a moderate chance of rain (60-70%) will be in place for all of Deep South Texas.

Rainfall totals are not expected to be excessive for our region, with DESI guidance suggesting only a 30-40% probability that any areas within the CWA will see more than an inch. Therefore, any rain that falls is expected to be beneficial. Conditions will begin to dry out Monday, with low to moderate (20-40%) precip chances continuing for areas east of I-69C. The driest days next week will be Tuesday and Wednesday. Another shortwave disturbance is possible on Thursday and Thursday night, bringing a low to moderate (20-50%) chance of rain to Deep South Texas.

A moderate risk of life-threatening rip currents is in effect for area beaches tonight and tomorrow. Most drowning deaths for our region occur in times when the risk is moderate (since surf looks more inviting on higher risk days), so any swimmers will want to exercise caution.

AVIATION

(18Z TAFS) Issued at 1138 AM CST Sat Nov 29 2025

VFR conditions are expected through the remainder of today with gusty southeasterly winds. Cloud cover is expected to become more widespread throughout the afternoon and ceilings are expected to lower, but still remain VFR. Showers are possible beginning around 14-15z tomorrow, which could decrease visibility to MVFR conditions. This is most likely to occur at BRO and HRL. Winds are expected to shift to a northerly direction around this time as well, as a strong cold front passes through the region.

MARINE

Issued at 1138 AM CST Sat Nov 29 2025

Marine conditions are expected to be hazardous to smaller vessels over the next few days as a strong cold front passes through the area. A Small Craft Advisory is currently in effect for the Bay and Gulf waters through this evening, and buoy readings are being monitored to see if any possible extension is warranted. Once winds drop below Small Craft Advisory conditions, Small Craft Exercise Caution conditions are expected.

Conditions should start improving on Tuesday night and remain more favorable with light to moderate winds and seas through Friday.

PRELIMINARY POINT TEMPS/POPS

BROWNSVILLE 68 77 51 61 / 20 80 70 30 HARLINGEN 63 74 47 58 / 20 70 70 20 MCALLEN 64 74 50 58 / 10 50 60 10 RIO GRANDE CITY 61 72 47 60 / 0 30 60 10 SOUTH PADRE ISLAND 72 76 57 64 / 30 80 80 40 BAYVIEW/PORT ISABEL 66 76 50 62 / 20 80 80 30

BRO WATCHES/WARNINGS/ADVISORIES

TX...High Rip Current Risk until 6 PM CST this evening for TXZ451-454- 455.

GM...Small Craft Advisory until 6 PM CST this evening for GMZ130-132- 135-150-155-170-175.