textproduct: Brownsville/Rio Grande Valley

KEY MESSAGES

Updated at 1232 AM CDT Mon May 4 2026

Key Messages:

* Building high pressure increases temperatures from the mid/upper 80s on Monday to mid/upper 90s on Wednesday while also warming afternoon heat indices, or "real feel temperatures," to near 100-105 F on Tuesday and 105-110 F on Wednesday.

* Minor (Level 1 of 4) Heat Risk on Monday escalates to a Moderate (Level 2 of 4) risk on Tuesday and a Moderate to Major (Level 3 of 4) risk on Wednesday.

* A cold front may pass through or stall late Wednesday night or Thursday, gradually increasing chances of rain to a low to medium (40-50%) chance Thursday night, followed by a daily low (15-25%) chance into this upcoming weekend.

* A medium risk of rip currents continues through at least Monday afternoon.

DISCUSSION

Issued at 1026 PM CDT Sun May 3 2026

A mid/upper level trough moves onshore the California coast on Monday, pushing a high pressure aloft eastward over Mexico and to the Gulf by midweek, aiding in increasing subsidence aloft and minimizing cloud coverage over Deep South Texas into Wednesday. Meanwhile, at the surface, lowering pressure falls over the Southern Plains and the Sierra Madre lead to increasingly breezier onshore southeasterly winds along/east of US-281, where gusts of 25-30+ mph are possible Tuesday and Wednesday afternoons, which will build relative humidity across the region. All these factors combined cause temperatures to climb from the mid/upper 80s on Monday to the mid/upper 90s on Wednesday, while also warming afternoon heat indices from mainly 100-105 F on Tuesday to mostly 105-110 F on Wednesday. Thus, Heat Risks deteriorate from a Minor Risk on Monday to a Moderate Risk on Tuesday and a Moderate to Major risk on Wednesday. The hottest indices are expected to be along the southern border, stretching from the Middle to Upper RGV, where apparent temperatures may briefly exceed these ranges by a few degrees for an hour or two. Overnight lows warm from the 60s tonight to the 70s for the remainder of the forecast, generally ranging around 5-8 degrees above average.

Then, a bit of a pattern change brings *some* relief to end the week. The trough mentioned above lifts northeastward over the Southern Plains on Wednesday and surface high pressure and northerly winds on the backside of the associated surface low push a cold front into southern Texas, either passing through or stalling near, or across, our CWA, possibly Wednesday night or Thursday morning into Friday. Frontal lift and moisture pooling in conjunction with enhancing forcing and ascension aloft, downstream of a slow-moving upper level cut-off low to the west, are currently anticipated to gradually increase chances of rain from late Wednesday night or Thursday morning to as much as a medium (40-50%) chance Thursday night as showers and thunderstorms develop. Despite increasing chances of rain and clouds, Thursday afternoon temperatures and heat indices could still reach into the lower 90s and lower 100s, respectively, with a Minor to Moderate Heat Risk. Friday may be the coolest day of the forecast as overcast skies could keep temperatures in the 80s. Otherwise, temperatures gradually rise back to the 90s by Sunday while a low (15-25%) chance of daily diurnally-driven convection continues, with shower and thunderstorm activity peaking in the afternoon.

Given that we are several days away from unsettled weather and confidence is low at this point, we will be keeping a close eye for any possibility of strong to severe thunderstorms and excessive rainfall, beginning Wednesday night or Thursday and persisting into this upcoming weekend, resulting from the front and/or mid- level disturbances running out ahead of the cut-off low pressure aloft behind the front.

Alongshore southeasterly winds and 3-4 foot waves with 6-7 sec. periods result in a medium risk of rip currents through at least Monday afternoon. Breezy winds throughout the week could continue to result in a moderate or low risk.

AVIATION

(06Z TAFS) Issued at 1232 AM CDT Mon May 4 2026

A few mid to high level clouds and light southeast winds prevail across Deep South Texas early this morning. Light southeast winds overnight will increase and become gusty in the late morning and afternoon. Some gusts between 20 to 25 knots will be possible in the afternoon, especially at BRO/HRL. VFR conditions are expected for the next 24 hours.

MARINE

Issued at 1026 PM CDT Sun May 3 2026

Mainly moderate to fresh winds, moderate (3-5 ft) seas and periods of Small Craft Exercise Caution headlines are likely through Friday, with winds transitioning from southeasterly to northeasterly or easterly on Thursday in association with a frontal boundary passing through or stalling over the Lower Texas coast. Gentle to moderate southeasterly winds resume over the weekend. Developing showers and thunderstorms result increase in chances of rain Thursday to as much as a low to medium (30-40%) chance Thursday night into Friday. A lingering low (15-20%) chance lingers into the weekend.

PRELIMINARY POINT TEMPS/POPS

BROWNSVILLE 85 75 90 77 / 0 0 0 0 HARLINGEN 87 71 92 75 / 0 0 0 0 MCALLEN 88 75 95 78 / 0 0 0 0 RIO GRANDE CITY 88 72 98 75 / 0 0 0 0 SOUTH PADRE ISLAND 80 76 83 77 / 0 0 0 0 BAYVIEW/PORT ISABEL 84 73 89 76 / 0 0 0 0

BRO WATCHES/WARNINGS/ADVISORIES

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