textproduct: Brownsville/Rio Grande Valley

KEY MESSAGES

Updated at 1047 PM CDT Sun Mar 15 2026

Key Messages:

* Strong cold front (modified Arctic airmass) arrives tonight; temperatures by Monday morning will have plummeted 40-50F degrees from Sunday afternoon's highs.

* Strong to potentially damaging winds develop tonight into Monday; northerly winds 25-35 mph are expected to gust as high as 45-55 mph with local gusts as high as 55-60 mph.

* A Red Flag Warning (RFW) for a critical fire weather risk is in effect for all of Deep South Texas, excluding the island till 7 PM CDT Monday; Fire Danger ranges between Very High and Extreme.

* Hazardous marine/coastal conditions likely though Monday; A Gale Warning is in effect for the Laguna Madre and Gulf Waters till 7 PM CDT Monday.

DISCUSSION

Issued at 1047 PM CDT Sun Mar 15 2026

After today's heat spike, which resulted in McAllen tying it's record high of 103F set back in 2008, courtesy of strong compressional heating from a nearby dryline and strong southerly winds, a significant change to the weather pattern is just about underway for all of Deep South Texas and the Rio Grande Valley.

Driven by an anomalously strong and emerging 591-591 dam Sonoran heat ridge over the Southwestern U.S. and a mature (neutrally- tilted) powerhouse mid-latitude cyclone over the Midwest/Great Lakes Region, that's producing combination of blizzard conditions in it's cold sector and severe weather in it's warm sector, a very strong cold front (modified Arctic front) will sweep through all of Deep South Texas and the Rio Grande Valley tonight.

Accompanying this cold front will be a 40-50F degree drop off in temperatures from this afternoon to Monday morning along with strong to damaging northerly winds 25-35 mph gusting as high as 45-55 mph late tonight into Monday. There could be an isolated case where wind gusts reach 55-60 mph. Multiple hazards, including fire weather and coastal/marine are in effect through the day on Monday in response to the Arctic front and impending weather changes.

Latest radar scans and sfc analysis shows the cold front quickly advancing southward over Corpus Christi's county warning area (CWA) and knocking on the doors of the Northern Ranchlands. Expect for this cold front to push through Deep South Texas from north to south between midnight and 4am. Along and behind the cold fropa, an enhanced pressure and thermal (isollabaric) gradient will result in strong to at times damaging winds. North-northeast winds 25-35 mph are expected to gusts as high as 45-55 mph with isolated gusts up to 60 mph. Isolated power outages are possible, so be prepared. A WIND ADVISORY remains in effect for all of Deep South Texas till 8 AM CDT and for Brooks, Kenedy, Hidalgo, Willacy, and Cameron counties till 1 PM CDT Monday.

Through tonight, following the cold fropa, temperatures will plummet as these winds will usher in a modified Arctic airmass into the region. By Monday morning, wake up temperatures will be in the upper 40s across parts of the Northern Ranchlands to the mid 50s along the Rio Grande Valley. Amid additional cool air advection (CAA) and the modified Arctic airmass still building into the region, Monday will feature the coolest day of the week with daytime highs struggling to make it out of the 60s, some 30-40F degrees cooler than the highs on Sunday, and ~15F degrees cooler than normal. With the cool airmass fully locked in over the region on top or sufficient radiational cooling on clearing skies, a cold night looms Monday night with overnight lows mainly in the 40s with 50s found along/near the coast.

Low relative humidity (RH) values and windy conditions on top of an ongoing drought will result in critical fire weather risk with the potential for fuels becoming combustible upon fire ignition on Monday across Deep South Texas. A Red Flag Warning (RFW) remains in effect for all of Deep South Texas, excluding the island from 10 PM CDT tonight to 7 PM Monday (see FIRE WEATHER SECTION for more details). These strong winds will also create hazardous marine and coastal conditions tonight through Monday (SEE MARINE SECTION for more details).

Beyond Monday night, a warming trend is expected to take place through the remainder of the forecast period. By Thursday, temperatures are expected to return to unseasonable warm levels (80s/90s) across Deep South Texas and the Rio Grande Valley.

AVIATION

(00Z TAFS) Issued at 622 PM CDT Sun Mar 15 2026

Through 00z Tuesday....The main weather concern to aviation ops for the terminals through the forecast period will be the strong to potentially damaging northerly winds developing later tonight into Monday, which will likely have major impacts/implications particularly to east to west oriented runways.

VFR conditions, by and large, will prevail through the 00z TAF cycle. There could be a few MVFR-LIFR clouds at times, particularly tonight.

Ahead of an approaching cold front, winds will continue out of the south with speeds between 7-15 kts, occasionally gusting as high as 20 kts through the evening hours before fading. In response to the cold fropa later this tonight, winds will shift out of the north and become strong with speeds between 15-25 kts. Winds will gusts generally between 35-45 kts, however, there could be isolated gusts as high as 50 kts or so on Monday.

MARINE

Issued at 1047 PM CDT Sun Mar 15 2026

A Gale Warning is in effect for the Laguna Madre and Gulf Waters till 7 PM CDT Monday. North-northeast winds 25-35 knots gusting up to 40 knots or so is expected. This will drive up high seas with wave heights ranging between 13-18 feet. Monday night through Tuesday, marine conditions (seas) will improve in response to the return of lighter winds. By Wednesday, favorable marine conditions are expected to return with low to moderate winds and seas. Favorable marine conditions will prevail through the remainder of the forecast period.

FIRE WEATHER

Issued at 1047 PM CDT Sun Mar 15 2026

A Red Flag Warning (RFW) is in effect for all of Deep South Texas, excluding the island till 7 PM CDT Monday. The combination of low relative humidity (RH) values, windy conditions, and an ongoing drought ranging from D2 Severe to D4 Exceptional, will result in critical fire weather risk on Monday. Any fires that ignite under these conditions will have the potential to become combustible and rather aggressive. We continue to urged everyone to not burn on Monday and continue to exercise safe fire weather conditions.

The Texas A&M Forest Service has outlooked the region under a Very High to Extreme Fire Danger for Monday. Energy Release Component (ERC) values will be high across the region on Monday ranging between 75- 100%. Finally, fuels will be dry to critically dry on Monday.

Additional fire weather concerns are possible through next weekend due to a continuation of at times low relative humidity levels and breezy conditions, in addition to an ongoing drought.

PRELIMINARY POINT TEMPS/POPS

BROWNSVILLE 59 64 53 72 / 20 0 10 10 HARLINGEN 52 66 47 72 / 10 0 0 0 MCALLEN 55 68 49 76 / 10 0 0 0 RIO GRANDE CITY 52 68 47 75 / 0 0 0 0 SOUTH PADRE ISLAND 59 62 58 67 / 20 10 10 10 BAYVIEW/PORT ISABEL 56 63 53 70 / 20 0 0 10

BRO WATCHES/WARNINGS/ADVISORIES

TX...Red Flag Warning until 7 PM CDT Monday for TXZ248>255-351- 353>355.

Wind Advisory until 8 AM CDT Monday for TXZ248-249-252.

Wind Advisory until 1 PM CDT Monday for TXZ250-251-253>255-351- 353>355-451-454-455.

High Rip Current Risk from 7 AM CDT Monday through Monday evening for TXZ451-454-455.

High Surf Advisory from 7 AM to 7 PM CDT Monday for TXZ451-454- 455.

GM...Gale Warning until 7 PM CDT Monday for GMZ130-132-135-150-155- 170-175.