textproduct: Brownsville/Rio Grande Valley

KEY MESSAGES

Updated at 534 PM CST Fri Mar 6 2026

Key Messages

* Unseasonably warm and at times breezy conditions will prevail through next week.

* While most days will be rain-free, there will be at least a couple of opportunities for some much needed rainfall through next week, as the weather pattern finally attempts to turn a bit more active.

* The best chance for showers and storms will be over the weekend (Saturday PM through Sunday PM); best chance north and west. * There is a Marginal chance (isolated chance) for strong to severe thunderstorms over the Northern Ranchlands and Starr County on Saturday.

* Moderate winds will maintain mainly moderate to adverse seas through next week.

DISCUSSION

Issued at 134 PM CST Fri Mar 6 2026

Unseasonably warm and at times breezy conditions under a southwest flow aloft regime will persist across Deep South Texas and the Rio Grande Valley through the forecast period or through next week. While mainly dry/rain-free conditions will persist, the prospects of showers and thunderstorms are expected to increase. In fact, the latest series of model runs has indicated that there may be a couple of opportunities for some much needed (beneficial) rainfall across at least parts of the region through next week. It's been nearly 3 months (since mid-December) in which we've seen rain of 0.25 inches or more across the region. Before mid- December dating back to November, rainfall has been far and few in between. This dry spell that we've been in has been quite remarkable. The latest drought information from the U.S. Drought Monitor shows drought conditions deepening and expanding across Deep South Texas and the Rio Grande Valley with 71% of our county warning area (CWA) now under a D3 (Extreme Drought) to a D4 (Exceptional Drought), with Exceptional Drought encompassing all of Jim Hogg, most of Brooks, eastern Zapata, and far northern Starr counties.

We start off the forecast period today where the latest GOES-19 visible satellite imagery showers a SCT-OVC deck of strato-cumulus clouds overhead. Expect for these trends to remain consistent through the day today. A tight pressure gradient, driven by a weak low/shortwave trough to our west over the Sierra Madre and high pressure over the Gulf Waters, a strong 25-40 kt low level jet (LLJ) overhead, combined with local topographical effects has activated the "Valley Wind Machine". Peak winds so far this afternoon at our local climate sites are as follows: 42 mph at Brownsville/South Padre Island International Airport (KBRO), 46 mph at Valley International Airport in Harlingen (KHRL), and 35 mph at Miller International Airport in McAllen (KMFE). Expect for these winds to persist through this afternoon before waning some later this evening after sunset as mixing heights decrease. Expect for a mild and at times breezy night ahead. The combination of insulation from a BKN- OVC cloud deck and warm air advection (WAA) from southerly winds will keep overnight low temperatures in the 70s (well above climate norms or for early March standards).

Global and hi-res (CAM) models continue to depict a cold front sweeping through much of Texas on Saturday before slowing or stalling over South Texas (approximately the Laredo to Corpus Christi area. Additionally, a weak low pressure area/shortwave trough over the Sierra Madre is expected to move over Deep South Texas on Saturday. Meanwhile, some diffluence aloft and mid-upper perturbations/energies ahead of an emerging/strengthening 550-555 mb low off the Baja Peninsula is expected to move overhead Saturday into Sunday. These features coupled with increased atmospheric moisture content with precipitable water (PWAT) values ranging between 1.5-1.8 inches will result in increased atmospheric buoyancy and diurnal instability, effectively resulting in increased shower and thunderstorm chances over the weekend (both Saturday and Sunday). For Saturday night, we have categorical chances along and west of IH-69C and over the Northern Ranchlands, and medium (30-50%) chances over the lower to mid valley and along the coast. For Sunday, we have categorical chances over much of the CWA with medium chances (50%) over Brownsville towards South padre Island. Sunday night, we have low to medium (30-50%) chances along and west of IH-69C and low chances 20% east of IH-69C.

SBCAPE values between 1,000-2,000 J/kg and MLCAPE values between 500- 1,000 J/kg are amongst some of the items that would support the risk for thunderstorms reaching strong to severe limits. Overall, the best coverage and chances for showers and strong to severe storms will be west and north. That's where the 0-6km bulk shear values and Showalter values are higher, and jet dynamics are better. Capping further to the east-southeast may limit coverage and severity here. That said, the Storm Prediction Center (SPC) has placed the northwestern section of Zapata County under a Slight Risk for severe thunderstorms, the Northern Ranchlands and Starr County under a Marginal Risk for severe thunderstorms and the Rio Grande Valley under a general risk for thunderstorms on Saturday in it's latest SWODY2. Large hail and damaging winds are the primary threats.

Additionally, given the strong moisture content, any showers and thunderstorms will be capable of producing heavy rainfall. Despite the ongoing drought, localized flooding is possible, especially in instances of slow moving storms training over the same locations. Sunday will feature the chances for additional showers/storms, though severe weather is not expected at this time.

Early to mid next week, forecast models and ensembles continue to advertise a formidable low pressure system near or just off the coast of the Baja Peninsula translating eastward across northern Mexico into Texas. As the parent energy moves over Texas with additional impulses tracking overhead, there could be additional chances for showers and thunderstorms early to mid next week that we have to keep an eye on. Currently, the best chances will be placed further to our north across central Texas due to stronger forcing and jet dynamics. A cold front will be associated with this low pressure system and is progged to push through Deep South Texas in the Wednesday-Thursday timeframe.

Temperature anomalies through next week will remain above average with positive geopotential heights and a southwest flow aloft regime in place. High temperatures will run in the upper 80s to 90s most days with overnight lows in the 60s/70s. The exception will be on Sunday due to the rain-cooled atmosphere and additional chance for showers and storms. Highs on Sunday are expected to top out in the upper 70s northwest (i.e. Zapata County) to the mid-upper 80s along mid to lower valley. Highs will also be lower, but still above average on Thursday and Friday behind the cool fropa. Highs on Thursday and Friday will top out in the 80s most places with overnight lows mainly in the 50s.

AVIATION

(00Z TAFS) Issued at 534 PM CST Fri Mar 6 2026

Windy conditions (SE winds 15-20 knots, gusting to 20-30 knots) continue through sunset, decreasing to 10-15 knots, with gusts to 20-25 knots overnight tonight. MVFR ceilings are anticipated to develop early tonight across all terminals, persisting through sunrise Saturday morning, before VFR conditions return by mid- morning as southeasterly winds increase back to 15-20 knots, gusting to 25-30 knots.

MARINE

Issued at 134 PM CST Fri Mar 6 2026

Moderate southerly winds from an enhanced pressure gradient will maintain moderate to adverse seas (i.e. Small Craft Exercise Caution) through next week. A brief period of Small Craft Advisory (SCA) conditions can't be ruled out through next week. Low to medium shower and thunderstorm chances return this weekend and maybe again next week.

PRELIMINARY POINT TEMPS/POPS

BROWNSVILLE 72 87 72 86 / 10 0 30 50 HARLINGEN 69 91 69 87 / 10 0 40 60 MCALLEN 74 94 73 89 / 10 10 50 80 RIO GRANDE CITY 71 97 67 82 / 10 10 70 90 SOUTH PADRE ISLAND 71 79 72 78 / 10 0 30 50 BAYVIEW/PORT ISABEL 69 86 69 84 / 10 0 30 50

BRO WATCHES/WARNINGS/ADVISORIES

TX...High Rip Current Risk through late tonight for TXZ451-454-455.

GM...None.