textproduct: Brownsville/Rio Grande Valley

KEY MESSAGES

Updated at 1039 PM CDT Tue May 26 2026

Key Messages:

* A Severe Thunderstorm Watch remains in effect tonight for the Upper RGV and the Northern Ranchlands until 6 AM Wednesday morning, where scattered severe thunderstorms could produce scattered damaging winds of 58-75 mph winds and large to very large (1-2 in) hail. Strong to isolated severe thunderstorms are possible further south and east as well.

* A Marginal to Slight Risk (levels 1 and 2 of 4) of isolated to scattered flash flooding from excessive and heavy rainfall is outlined for the Upper RGV and Northern Ranchlands tonight as well as for areas along/east of US-281 on Wednesday.

* Strong to isolated severe thunderstorms could continue into Wednesday morning and/or re-develop Wednesday afternoon, though confidence is low at this time.

* A moderate risk of rip currents continues through Wednesday afternoon.

* Minor to moderate heat risks (level 1 and 2 of 4) persist, peaking this weekend as dry conditions and clearer skies temporarily resume.

DISCUSSION

Issued at 1039 PM CDT Tue May 26 2026

And once again, we are now staring down the barrel of another potential dark and stormy night here in deep south Texas. A deep and negatively-tilted mid/upper level trough persists overnight across northern and eastern TX, downstream of a strong trough/cut-off low aloft digging southward over the western US. The combination of Pacific (via southwesterly 700 mb flow) and Gulf (via lower level southeasterly flow) moisture transport into the area of increased forcing for ascension aloft has resulted in numerous severe thunderstorms across western, central and southern Texas today and this evening, with the southernmost portion of activity currently producing a squall line extending south-southwestward from just east of San Antonio on down to Webb and Duval counties, just north of the Northern Ranchlands, generally moving due east. Meanwhile, overcast skies loom over our region along with dry conditions. The latest SPC Mesoanaylsis indicates 7.0-7.5 C/km mid-level lapse rates and 35-45+ kt bulk shear across most of the region as well as SBCAPE and MUCAPE values of 3,000-4,000 J/kg (highest along/west of US-281) in addition to 500 mb analysis showing the best upper level flow divergence across the Northern Ranchlands, all of which is setting the stage for strong to severe thunderstorms anticipated over the coming hours.

The HRRR continues to be more or less the best in accurately initializing the latest regional conditions/radar and this evening's 00Z run indicates the area of developing convection over the Sierra Madre/northwest of Zapata County to intensify and lengthen southward, bringing the possibility of strong to scattered severe thunderstorms, potentially along another squall line, eastward into Zapata, Starr, Jim Hogg, Brooks and Kenedy counties late tonight, where there is a Severe Thunderstorm Watch effective until 6 AM Wednesday morning. The primary threats across this area continue to be damaging winds of 58-75 mph and large to very large (1-2 inch) hail. Although Hidalgo, Cameron and Willacy counties are not part of this watch due to less instability, conditions are still supportive for strong to isolated severe thunderstorms, still capable of producing strong to isolated damaging winds and small to isolated large hail. Additionally, as PWATs could surge to as high 2.0-2.30 in. overnight, these storms are likely to be efficient rainfall producers with the capability of easily producing 1-3+ inches where thunderstorms move slowly or train. Therefore, WPC maintains a Slight Risk of scattered flash flooding from excessive and heavy rainfall over the northern portions of Zapata, Jim Hogg and Brooks counties as well as a Marginal Risk for isolated flash flooding to as far south as southeastern Starr, northwestern Hidalgo and northwestern Kenedy counties.

Whatever is left of the convective activity by Wednesday morning should continue to move eastward and be mostly over the Gulf, possibly by mid-morning, followed by a low to medium (30-60%) chance of showers and thunderstorms in the afternoon and early evening hours. However, due to run-to-run model inconsistency in timing and convective mode(s), it is less certain for the prospects of severe thunderstorms either continuing in the morning and/or redeveloping in the afternoon. Yet, these aspects should gain more confidence overnight tonight as the convection unfolds. Still, high moisture content leads to a Marginal Risk of isolated flash flooding mainly along/east of US-281, as far west as the far eastern portions of Jim Hogg County and northern/eastern half of Hidalgo County.

Ridging resumes behind the departing trough Wednesday night with a dry stretch ensuing into the weekend, when troughing over Mexico and the Desert Southwest begin to bring some more daily chances of unsettled weather, possibly beginning Saturday night. Chances remain low to medium (20-40%) at this time, though could become more widespread and persistent by early next week.

High temperatures in the low/mid 90s, possibly upper 80s further north, continue through most of the next 7 days along with maximum afternoon heat indices ranging within a few degrees from 100-105 F. Mainly minor heat risks can be expected across most of the region each day though more urban areas of the RGV could experience moderate. As moisture and heat build again from southeasterly winds and increased sunshine late this week and into this weekend, a moderate risk could become more widespread across the RGV Friday into Saturday and across the rest of the region on Sunday before reducing to mostly minor early next week as cloud cover increases. Heat indices up to 110 F are possible within the moderate heat risks.

A moderate risk of rip currents continues through Wednesday afternoon.

AVIATION

(00Z TAFS) Issued at 613 PM CDT Tue May 26 2026

Gentle to moderate (10-15 knots, gusting to 20-25 knots) east- southeasterly to southeasterly winds and scattered to broken VFR skies could continue through most of tonight. Confidence is currently to low medium, but the impact risks are high for strong and isolated to scattered severe thunderstorms late tonight, bringing the potential of damaging (50+ knot) winds and small to large (1+ hail) hail late as well as potential periods of lower ceilings and reduced visibility late tonight. The higher probabilities of more scattered severe thunderstorms are over KMFE, perhaps arriving and passing through around 08-12 Z late tonight into tomorrow morning. Chances of severe thunderstorms decrease from west to east, arriving an hour or two later over KHRL and KBRO, where strong (less than 50 knot) to isolated damaging winds and small to large hail are still possible. MVFR ceilings are expected to either assist and/or follow convection into tomorrow morning, remaining broken to overcast though rising back to VFR into the Wednesday afternoon hours. Southeasterly winds pick back up tomorrow afternoon to similar magnitudes as today. Expect amendments throughout the 00 Z TAF cycle.

MARINE

Issued at 1039 PM CDT Tue May 26 2026

Small Craft Exercise Caution headlines, resulting from moderate to fresh winds and moderate (3-5 ft) seas are likely to continue through tonight before easing to mainly gentle to moderate easterly to southeasterly winds and slight to moderate (2-4 ft) seas for the remainder of the next 7 days. Chances of rain gradually increase throughout tonight to as much a medium (40-60%) chance Wednesday morning and gradually diminish to around 15% or less from Thursday into this weekend. Low to medium chances of rain return either late this weekend or early next week.

PRELIMINARY POINT TEMPS/POPS

BROWNSVILLE 80 90 78 92 / 10 30 10 20 HARLINGEN 77 91 75 92 / 20 40 10 20 MCALLEN 78 93 77 94 / 30 30 20 10 RIO GRANDE CITY 75 94 75 94 / 40 20 10 10 SOUTH PADRE ISLAND 81 85 80 85 / 10 30 20 10 BAYVIEW/PORT ISABEL 79 89 78 90 / 20 30 10 10

BRO WATCHES/WARNINGS/ADVISORIES

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