textproduct: Brownsville/Rio Grande Valley

KEY MESSAGES

Updated at 614 AM CDT Tue May 26 2026

Key Messages:

* SPC continues a Marginal Risk (level 1 of 5) of isolated severe thunderstorms, with a primary threat of damaging winds, across all of deep south Texas as well as a secondary threat of isolated large to very large hail across portions of the Upper RGV and Rio Grande Plains Tuesday/Tuesday night.

* WPC maintains a Marginal Risk (level 1 of 4) of isolated flash flooding from excessive and heavy rainfall across the Northern Ranchlands and Rio Grande Plains on Tuesday/Tuesday night as well as the coastal counties and portions of the Northern Ranchlands and Middle RGV on Wednesday.

* There are additional chances of strong to isolated severe thunderstorms on Wednesday and Thursday, though confidence is low at this time. Otherwise, drier weather returns Wednesday night and through the end of the work week/early weekend. Unsettled weather may return later weekend/early next week.

* Daily minor to moderate (levels 1 and 2 of 4) heat risks and maximum afternoon heat indices of 95-105 F (locally hotter) continue, possibly peaking over the weekend.

* A low risk of rip currents persists through Tuesday afternoon.

DISCUSSION

Issued at 1026 PM CDT Mon May 25 2026

A strong mid/upper level trough digs from the PNW to the western US, advancing another trough eastward over the Desert Southwest to western Texas by midweek, thus resulting in a gradual increase in forcing and ascension aloft. This, along with southeasterly flow re- enhancing surface moisture beginning tonight, should build cloud cover across deep south Texas through the next 24 hours. At this time, we anticipate a low (15-30%) chance of showers and thunderstorms developing over the Rio Grande Plains Tuesday morning and spreading eastward across the entire region into the afternoon and evening hours. Chances of rain could reach as high as a low to medium (30-60%) chance Tuesday night, highest across the Northern Ranchlands. This is more in alignment with this evening's cam guidance, which now generally suggest increased cloud cover and reduced surface- based instability leading to more stratiform light to moderate showers and a few sub-severe, though potentially locally strong, thunderstorms capable of producing gusty winds and locally heavier rain through the morning and afternoon hours on Tuesday before another round Tuesday night, when strong to isolated thunderstorms are possible across the Rio Grande Plains and Northern Ranchlands.

Yet, should a further delay in the arrival of divergence aloft result in more sparse cloud cover and lower rain chances during the day on Tuesday, the probabilities of strong to isolated severe thunderstorms during the afternoon and/or overnight hours could increase considerably. Therefore, SPC continues a Marginal Risk of isolated severe thunderstorms for Tuesday and Tuesday night, with the primary risk of isolated damaging (58+ mph) winds across all of deep south Texas as well as a secondary threat of isolated large (1+ inch) hail across Zapata County and the far western portion of Starr County if Sierra Madre convection makes it to the border. Very large (2+ inch) hail is even possible near and along the Rio Grande/US border in northern Zapata County. This conditional and hypothetical scenario could also be supportive of producing a squall line across all, or portions, of the CWA Tuesday night. Additionally, as PWAT values rise to as much as 1.9 to 2.2 in. Tuesday into Wednesday, WPC keeps the majority of the Northern Ranchlands and the Rio Grande Plains within a Marginal Risk of isolated flash flooding from excessive and heavy rainfall Tuesday and Tuesday night. More specifically, this includes most of Zapata County (except the southern portions), all of Jim Hogg county, most of Brooks County (except the southeastern areas) and the northwestern part of Kenedy County.

A low to medium (30-60%) chance of showers and thunderstorms continues through Wednesday morning and afternoon as the trough passes over our region. Currently, SPC outlines a general outlooks of sub-severe thunderstorms on Wednesday. However, a strong to severe thunderstorm, or two, is not out of the question, especially if a potential squall line is still working its way through the region into the daytime, perhaps over the eastern portions of the CWA. As such, SPC could add a Marginal Risk within the next few updates. WPC maintains a Marginal Risk of isolated flash flooding from excessive rainfall from the eastern half of Jim Hogg and Hidalgo counties on eastward to the coast for Wednesday. By Thursday morning, we expect rainfall amounts to range from a trace to as much as 0.5 an inch across the RGV, while the Rio Grande Plains and the Northern Ranchlands could receive 0.5 to 0.8 of an inch. However, due to very high moisture content favoring efficient heavy rain production, localized rainfall rates of up to 3 in./hr could produce 1 to 3+ inches within the deepest convection, especially in slow-moving thunderstorms or where thunderstorms train over an area one after the other.

Ridging behind the departing trough resumes and brings much drier conditions Wednesday night. Minimal (<10%) chances of rain could persist through the remainder of the work week, possibly into Saturday. Yet, the 00Z RRFS and 18Z GFS portray an embedded mid- level shortwave passing over on Thursday, bringing the possibility of strong to isolated thunderstorms. However, confidence remains low at this time. Otherwise, the next chance of unsettled weather arrives possibly Saturday night into next Monday as the upper level trough over the western US advances eastward. PoPs are low to medium at this time. High temperatures continue to rise to the upper 80s and 90s along with heat indices generally ranging from 95-105 F. Minor to moderate heat risks continue across the RGV and coastal counties, where indices could briefly peak as high as 110 F. More abundant sunshine results in a more widespread moderate heat risk on Friday and Saturday. Overnight lows continue in the 70s.

A low risk of rip currents continues through Tuesday afternoon.

AVIATION

(12Z TAFS) Issued at 614 AM CDT Tue May 26 2026

Through 12z Wednesday....VFR conditions, by and large, will prevail through the 12z TAF cycle. The exception could be during the overnight hours into the early-mid morning hours where MVFR-IFR mist/low stratus could develop or be around.

Rain or thundershowers are possible later this morning over all the terminals with the greatest chance being over KMFE. Another round of showers and thunderstorms are possible later tonight into Wednesday. Currently, have Prob30 groups for KMFE. Any showers or storms will have the capabilities of reducing cigs/vsbys down to MVFR-IFR. We'll continue to monitor trends and make amendments as needed.

If not light and variable, winds will be light out of the southeast with speeds up to 5 kts through the overnight. During the day today, light and variable winds are expected to pick up out of the southeast with speeds between 5-15 kts and gusts up to 25 kts.

MARINE

Issued at 1026 PM CDT Mon May 25 2026

Gentle to moderate easterly to southeasterly winds and slight to moderate (2-4 ft, occasionally higher) seas persist through the next 7 days. Small Craft Exercise Caution headlines are possible for the Laguna Madre and nearshore Gulf Waters (0-20 nm) Tuesday and Wednesday afternoon/evening in response to a slight locally enhanced pressure gradient, resulting in moderate to fresh winds. Chances of showers and thunderstorms increase Tuesday night to as much as a low to medium (3-60%) chance during the day on Wednesday. Strong to isolated severe thunderstorms are possible as well. Chances gradually diminish Wednesday night and much drier conditions resume through this weekend before the next system brings unsettled weather, possibly by early next week.

PRELIMINARY POINT TEMPS/POPS

BROWNSVILLE 90 80 91 79 / 10 20 30 20 HARLINGEN 91 77 91 75 / 20 30 40 10 MCALLEN 91 78 93 77 / 20 40 30 10 RIO GRANDE CITY 91 75 94 75 / 20 40 10 10 SOUTH PADRE ISLAND 85 81 86 80 / 10 30 30 20 BAYVIEW/PORT ISABEL 89 79 90 78 / 10 30 40 20

BRO WATCHES/WARNINGS/ADVISORIES

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