textproduct: Brownsville/Rio Grande Valley

KEY MESSAGES

Updated at 1235 AM CDT Fri May 22 2026

Key Messages:

* An active weather pattern continues, featuring daily chances of showers and thunderstorms as well as an ongoing non-zero probability of strong to isolated severe thunderstorms capable of producing large (1+ inch) hail, damaging (58+ mph) winds and heavy rain. A Flood Watch remains in effect through Sunday night.

* There is an increasingly stronger signal for strong to severe convection and heavy rain on Saturday, prompting SPC and WPC to place the entire region within a Marginal Risk (level 1 of 5) of isolated severe thunderstorms and a Slight Risk (level 2 of 4) of scattered flooding from excessive rainfall, respectively.

* A mostly Minor Heat Risk (level 1 of 4) continues through most of the forecast period, with afternoon heat indices peaking around 95-105 F.

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

DISCUSSION

Issued at 1019 PM CDT Thu May 21 2026

A very active and wet pattern continues across deep south Texas through most of this weekend and into next week, featuring daily elevated chances of rain from rounds of showers and thunderstorms, some of which could be strong to severe, capable of producing large (1+ inch) hail as well as strong and damaging winds (58+ mph). Along with the potential for severe weather, unusually high moisture content (PWAT exceeding 2.0 in. at times) will likely lead to rounds of heavy rain on top of an increasingly saturated ground and a Flood Watch remains in effect for the entire region through Sunday night. Tonight through Monday morning, we generally expect most areas to receive an additional 0.5-1.5 inches of rain though portions of the Northern Ranchlands could pick up closer to 2.0 inches. Of course, other locations, in which heavy rain develops or persists, could see locally higher amounts, with 2-4+ inches possible in the deepest convection, perhaps within just a few hours in a few spots. Yet, this continues to be a dynamic situation, so all of these forecast amounts are subject to change. Throughout this timeframe, saturated soil and urban poor drainage could lead to isolated to scattered flash flooding.

In the meantime, a mid/upper level shortwave over the northern- central Rockies, downstream of an eastward-moving trough aloft offshore the Baja Peninsula, maintains lowered 500 mb heights through tonight as it moves over the Northern and Central Plains, leading to a low to medium (20-40%) chance of showers and sub-severe thunderstorms tonight along/west of US-281. The trough mentioned above lifts northeastward into Canada on Friday, thus rising heights and falling PWAT values lead to a drier and more stable atmosphere on Friday aside from a low (15-30%) chance of showers and thunderstorms along a seabreeze boundary along/east of US-281 Friday afternoon and a 15-30% chance chance along/west of US-281 overnight as an impulse could pass over ahead of the trough moving over northern Mexico and into western Texas. SPC maintains a general risk of sub-severe thunderstorms through Friday night.

Activity really begins to pick back up on Saturday as upper level divergence maximizes and stronger mid-level impulses pass over in association with the trough arriving over central and southern Texas, leading to a stronger signal of strong to isolated severe thunderstorms carrying the threat of both large hail and damaging winds as well as heavy rain. The latest deterministic runs of the RRFS and GFS portray rounds of convection occurring during the daytime and continuing into Saturday night. This afternoon's 18Z RRFS even portrays slow-moving or stationary strong to severe cells developing Saturday afternoon, which could further exacerbate flooding potential. As such, SPC and WPC have already included all of our CWA within a Marginal Risk of isolated severe thunderstorms and a Slight Risk of scattered excessive rainfall, respectively, with the primary threats of isolated large hail and damaging winds as well as scattered flooding resulting from excessive and heavy rainfall. Future updates may enhance or lessen these severe and flooding categorical probabilities. Following, a medium to likely (40-70%) chance of rain continues into Sunday, highest along/east of US-281, where WPC holds a Marginal Risk of excessive rainfall as troughing persists aloft.

Chances of rain gradually lessen to a low (15-30%) chance of rain early next week as troughing subsides over Texas before increasing again by the middle of next as the next trough arrives over the Desert Southwest. Temperatures are generally expected to maximize in the upper 80s/low 90s during the afternoon and minimize in the 70s overnight. A Minor Heat Risk is expected each afternoon as heat indices peak around 95-105 F.

Finally, a moderate risk of rip currents continues through Friday afternoon.

AVIATION

(06Z TAFS) Issued at 1235 AM CDT Fri May 22 2026

MVFR to VFR will prevail at the aerodromes through the next 24 hours. Breezy winds will occur during the daylight hours with lighter winds at night. Convection is not forecast or expected to occur.

MARINE

Issued at 1019 PM CDT Thu May 21 2026

Gentle to moderate easterly to southeasterly winds and slight to moderate (2-5 ft) seas continue through the forecast. Chances of rain increase on Saturday to as much as a medium to likely (40-80%) chance Saturday night and gradually decrease into the early parts of next week before picking back up by the middle of next week. There is a chance for strong winds (34+ knots) and large (1+ inch) or small hail on Saturday and Sunday as well as an ongoing non-zero chance of strong to isolated severe throughout the forecast. These probabilities are subject to change.

PRELIMINARY POINT TEMPS/POPS

BROWNSVILLE 92 79 91 77 / 10 20 50 60 HARLINGEN 92 76 90 74 / 10 20 60 60 MCALLEN 93 77 91 75 / 20 30 60 60 RIO GRANDE CITY 93 75 90 73 / 10 30 60 60 SOUTH PADRE ISLAND 85 80 85 79 / 10 20 40 60 BAYVIEW/PORT ISABEL 90 78 89 76 / 10 20 50 60

BRO WATCHES/WARNINGS/ADVISORIES

TX...Flood Watch through Monday morning for TXZ248>255-351-353>355- 451-454-455.

GM...None.