textproduct: Brownsville/Rio Grande Valley

KEY MESSAGES

Issued at 114 PM CST Thu Nov 5 2026

- A rainy pattern is expected to set overnight and continue through the weekend, with widespread moderate (50-90%) to high chances.

- All of Deep South Texas is under a Marginal (level 1 of 4) Risk of Excessive Rainfall Saturday and Sunday. Isolated flash flooding is possible in areas that receive heavier rainfall.

- Cooler temperatures will continue through the end of next week following the frontal passage. Temperatures will be pleasant with highs in the 70s and 80s.&&

DISCUSSION

Issued at 114 PM CST Thu Nov 5 2026

A cold front is expected to move through the region overnight, which will cool temperatures below seasonal levels and set up a rainy pattern that will continue through the weekend. Conditions this afternoon should be overall rain-free (albeit humid as the atmosphere becomes increasingly moist), but rain chances will begin to increase tonight after 7 pm as the front approaches the area.

Tonight, instability is expected to increase due to a combination of an approaching front, increased troughing, and highest moisture. Chances will be greatest over the Northern and Western Ranchlands (around 60 to 80%) ahead of the front as it moves towards and through the area. Chances will be moderate in the Lower Rio Grande Valley (40 to 50%)overnight. Tomorrow morning, the front will move through the lower part of the Valley, which will put the highest rain chances (70 to 80%) throughout the day. There will be a bit of a reprieve in the rain Friday night as the front moves away from the area before the next system arrives. The most likely precipitation amounts Thursday night through Friday afternoon should be between 0.5 to 1.5 inches for most areas, with locally heavier amounts possible.

A stronger mid to upper-level trough is expected to move across the Desert Southwest Friday and Saturday before arriving to Northern Mexico Sunday. This will bring divergent upper level flow right over Deep South Texas this weekend, which will provide sufficient lift for widespread moderate to high (50 to 90%) rain chances to continue Saturday into Sunday. Given the abundance of available moisture (high PWAT values ranging between 1.8 and 2.2 inches) and supportive upper-air dynamics, some areas could receive heavy rainfall over the weekend, particularly around the Coast. The Weather Prediction Center has placed all of Deep South Texas under a Marginal (level 1 of 4) Risk of Excessive Rainfall for both Saturday and Sunday, with the potential for a later upgrade to a Slight (level 2 of 4) Risk. Some areas that receive heavier rainfall could see isolated flash flooding.

Due to the overall setup associated with weekend trough, confidence is high that widespread rain will occur this weekend throughout South Texas. However, confidence is a little lower as to where exactly the heaviest rain will occur, as model guidance is not in complete agreement over the exact placement and dynamics of the trough. The GFS favors heavier precipitation closer to the Coastal Bend area, but the Euro and the RRFS favor heavier precipitation further south closer to the King Ranch area and the Lower Rio Grande Valley. The most likely rainfall totals for Deep South Texas between Saturday morning and Monday morning are between 2 and 4 inches. Some areas could see totals as high as 5 to 7 inches.

Rain chances will start to decrease on Monday but remain moderate ( 30 to 50%) as the upper-level trough moves away from the area. Conditions should then overall dry up the rest of the week for most areas, but low rain chances (20% or less) will persist for coastal areas through Thursday, as offshore showers are expected to continue throughout the week. Temperatures will remain pleasant and fall-like throughout the week, with highs in the 70s and 80s. Some areas in the Northern Ranchlands could see cooler highs in the upper 60s on Monday, which is expected to be the coolest day of the week. Lows will get down into the low-to-mid 50s and lower 60s Monday though Thursday.

AVIATION

(00Z TAFS) Issued at 609 PM CST Thu Nov 5 2026

Overall...takeoff and landing conditions should be relatively copacetic for the next 24 hours, despite the arrival of a period of rain/showers as early as pre-dawn and continuing through mid- late afternoon before tapering off.

A wind shift line (not a true front) eases through the Rio Grande Valley later tonight into Friday morning, with winds backing to the north-northeast before daybreak and increasing a bit during the afternoon, as slightly drier surface air slides in. Aloft...a weak but noticeable 500 mb trough crosses the area during the late morning and early afternoon, bringing a period of persistent (categorical) light rain/showers with it. The main timing of this rain appears to be from early morning to around noon in McAllen, and late morning to mid afternoon at Harlingen and Brownsville. With no real cold air advection, ceilings should only drop to low VFR (3500-4500) and perhaps high MVFR if the rain falls a little harder than currently expected. Visibility should drop to 4-5 miles (high MVFR) in the still-humid airmass - and could briefly drop to or just below 3 miles if rain falls harder, suggested by model blends for McAllen/Miller during the mid-late morning. Updated forecasts at midnight (06Z) and daybreak (12Z) will provide more clarity. Aforementioned surface drying and passage of the disturbance should bring VFR visibility during the mid to late afternoon in all areas, though light rain/sprinkles may continue and ceilings, especially near the coast, in the 3500-4500 range.

MARINE

Issued at 114 PM CST Thu Nov 5 2026

Overall favorable conditions continue today and tomorrow into tomorrow night. Winds are then expected to pick up Saturday, with SCEC conditions expected Saturday and Small Craft Advisory conditions expected Saturday night into Sunday as a trough moves through the area. Conditions will then improve again Monday into Tuesday.

PRELIMINARY POINT TEMPS/POPS

BROWNSVILLE 73 81 70 81 / 40 90 30 50 HARLINGEN 70 80 67 79 / 50 80 30 50 MCALLEN 73 82 69 81 / 70 70 30 70 RIO GRANDE CITY 70 80 65 78 / 80 70 20 60 SOUTH PADRE ISLAND 74 78 73 78 / 50 80 40 60 BAYVIEW/PORT ISABEL 71 80 69 80 / 50 80 30 50

BRO WATCHES/WARNINGS/ADVISORIES

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