textproduct: Brownsville/Rio Grande Valley

KEY MESSAGES

Updated at 614 AM CDT Mon May 11 2026

Key Messages:

* Keeping an eye on potential severe weather, mainly damaging winds, for the Rio Grande Plains and Brush Country (Zapata, northern Starr, Jim Hogg) after midnight and before daybreak Monday

* Conditions should dry out quickly later Monday morning and continue through much of the work week, with slightly below average temperatures for mid-May and only a minor heat risk

* After some unsettled winds and surf Monday, favorable marine, coastal, and beach conditions dominate the rest of the work week

* Heat risk returns to moderate or higher levels by next weekend

DISCUSSION

Issued at 1054 PM CDT Sun May 10 2026

Rest of tonight through early Monday: The greatest potential for hazardous weather during the seven-day period exists right off the bat. After early evening isolated strong to severe storms in the upper Valley Sunday, conditions have quieted, for now. However, an expected squall line has formed, and as of 1030 PM extended from San Antonio through just south of Eagle Pass. A combination of CAMs models and incoming short-range models suggest that sensible overnight weather will feature highest rain chances - and severe weather threat in the form of damaging squall-line type winds - across the Rio Grande Plains/Brush Country areas of Zapata, Jim Hogg, and northern Starr...perhaps extending into Brooks and Kenedy, arriving between 1 and 3 AM. For the rest of the area, including the populated Rio Grande Valley, increasing overnight stability and capping favor weakening/dissipating threat as the line...pushed by a weak front...moves southeast between 3 and 6 AM. Storm Prediction Center also agreed with this, as their 730 PM update alluded to weakening of the line into the increasingly stable/capped air.

All this said...surface air ahead of the boundary/line is quite warm and sticky, and the 00Z sounding was conditionally unstable with most unstable CAPE over 4K J/kg. So...if for some reason, a more robust squall line accelerates at pace late tonight (and a little earlier than expected), the populated RGV could see more pronounced activity just before daybreak. For now, that probability likely sits at 10% or less, so will not highlight.

As for rainfall...WPC has these areas outlooked for isolated flash flooding (marginal - level 1 of 4) but given the expected movement of any stronger cells, more nuisance flooding would be more the case.

The recently arrived blended suite of near-term forecast data matches this thinking, so no changes are planned.

Rest of Monday: Winds shift to the north/northeast and drier, more stable air filters in steadily. Rain chances should quickly end from northwest to southeast, but remnant clouds behind the front in north/northeast flow will keep temperatures several degrees below average (mainly 80s).

Monday Night through Thursday: If you have some time to spare, this is true "bonus weather" for the region, as we sit underneath the front side of a modest (for mid May) 500 mb ridge and the back side of fairly robust eastern U.S. troughing. Dry air slides across most of Texas Monday night and remains in place through Thursday, with lowering humidity, generally light northeast to east winds, and plenty of sunshine. May sun will bring afternoon highs into the upper 80s to low 90s, about 2-4 degrees below average...while mornings will dawn in the upper 60s to around 70 (mid 60s in preferred cooler spots) - also, 2-4 degrees below.

Thursday Night through Sunday: The eastern trough weakens/pulls away, and the 500 mb ridge that extended across all of Texas gets flattened to northern Mexico. Troughing passing through the southern Plains helps to bring surface troughing to west Texas, with the resulring increase in south/southeast flow for the region beginning Friday and dominating through the weekend. That ends the "bonus weather" quickly, and returns sultry nights and hot/humid days to the region. Moderate heat risk returns as apparent temperatures build back into the 103-107 range Saturday and Sunday.

AVIATION

(12Z TAFS) Issued at 614 AM CDT Mon May 11 2026

VFR conditions are expected for the TAF period at all TAF sites. While a high level cloud deck will persist through the period, the lowest that cloud deck is forecasted to be is around 5,000 feet. Mostly light winds out of the north will persist through the period while a few gusts could occur during the late morning and early afternoon hours.

MARINE

Issued at 1054 PM CDT Sun May 10 2026

Rest of Tonight through early Monday: The key concern will be impact from whatever remains of the south-central Texas convection/squall line by early Monday. Should the line hold together, we could see a short period of gale-force gusts due to any wake low/meso high developments, especially north of Port Mansfield. Otherwise, the concern would be lightning and brief downpours. Timing could line up with any early morning fishing trips, so boaters may wish to postpone trips until whatever storms there are no longer pose a threat.

Later Monday through Thursday: Freshening north/northeast winds will briefly build seas toward 4 feet Monday afternoon before high pressure ridge at the surface settles in for the remainder of this period, allowing winds to diminish back to 5-10 knots (from the east- northeast)and seas to become mainly slight (2-3 feet) with no additional rainfall.

Thursday night through Friday night: As the ridge moves into the eastern Gulf, southeast flow returns and gradually increases, with perhaps caution level winds arriving later Friday into Friday night.

PRELIMINARY POINT TEMPS/POPS

BROWNSVILLE 86 74 86 72 / 30 0 0 0 HARLINGEN 86 70 86 68 / 30 0 0 0 MCALLEN 86 73 88 71 / 30 0 0 0 RIO GRANDE CITY 86 72 87 71 / 20 10 0 0 SOUTH PADRE ISLAND 82 77 81 76 / 30 0 0 0 BAYVIEW/PORT ISABEL 85 74 85 72 / 30 0 0 0

BRO WATCHES/WARNINGS/ADVISORIES

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