textproduct: Brownsville/Rio Grande Valley

KEY MESSAGES

Updated at 1210 PM CDT Fri Sep 18 2026

- There is Moderate (level 2 of 4) Heat Risk this afternoon. Heat indices could climb over 108 across the Rio Grande Valley and Coastal Counties for an hour or two this afternoon.

- Low to moderate (20 to 50%) chance of showers and thunderstorms continue across Deep South Texas this afternoon, before conditions dry out tomorrow for the weekend.

- Rain chances return early next week and continue throughout the week. Heat Risk will continue as well.

- There is a moderate risk of rip currents at area beaches.

DISCUSSION

Issued at 1210 PM CDT Fri Sep 18 2026

An unsettled weather pattern continues over the next few days as an area of strong high pressure over the Southeastern CONUS continues to backbuild westward, with northeasterly upper level flow beneath the underside of of this high reaching Deep South Texas. Because this northeasterly airmass has spend considerable time over the Gulf, the atmospheric profile is expected to remain considerably moist this afternoon, with PWATs over 2 inches. This will support low to moderate (20 to 50%) rain chances this afternoon. The rain is expected to be overall beneficial, with most areas receiving no more than half an inch. However, some heavier showers and thunderstorms could cause locally heavier amounts with the potential for nuisance ponding.

As high pressure continues to build westward over northeastern Texas though the weekend, upper-level subsidence will keep conditions dry for the weekend. A shower or two cannot be completely ruled out along the sea breeze, but rain chances remain very low for both Saturday and Sunday.

Rain chances are expected to pick up again next week as more moist air is advected into the region as northeasterly flow continues. Sea breeze activity is possible each day next week. However, longer-range guidance is not in agreement as to whether the upper level ridge over northeast Texas is going to continue through next week, or begin to break down as a trough approaches from the west. While the current NBM guidance is supporting low to moderate (20 to 40%) PoPs starting Tuesday, this could trend higher or lower depending on the behavior of the high pressure system and the trough to our west. Chances could decrease if the high pressure stays stronger over Texas, but we could see an increase in widespread rain chances if the approaching trough is able to break down the ridge and produce any shortwave disturbances as it approaches.

Heat Risk will remain a concern over the next week. Though increased cloud cover and rain chances may bring some small temperature relief by a few degrees, the humid airmass will continue to keep heat indices high. Heat indices will be elevated today, with some areas exceeding 108 degrees for an hour or two this afternoon. We will likely see more elevated heat indices this weekend as well.

There is a moderate risk of rip currents at area beaches today.

AVIATION

(18Z TAFS) Issued at 1210 PM CDT Fri Sep 18 2026

VFR conditions are expected at all airports, but a TEMPO has been added for showers and thunderstorms, as we are presently seeing scattered convective activity develop throughout Deep South Texas. If a shower or thunderstorm happens to occur near the airport, it could temporarily deteriorate conditons. Otherwise, light to moderate northeasterly winds are expected with few clouds.

MARINE

Issued at 1210 PM CDT Fri Sep 18 2026

Favorable conditions are expected over the next several days with light to moderate northeasterly winds and low to moderate (2-4 feet) wave heights. Offshore showers and thunderstorms are possible throughout next week, which could temporarily deteriorate conditions in their immediate vicinity.

PRELIMINARY POINT TEMPS/POPS

BROWNSVILLE 95 79 95 78 / 30 0 10 0 HARLINGEN 97 75 98 74 / 30 0 10 0 MCALLEN 99 78 100 78 / 50 0 10 0 RIO GRANDE CITY 99 77 101 77 / 40 10 0 0 SOUTH PADRE ISLAND 89 81 89 81 / 30 20 20 0 BAYVIEW/PORT ISABEL 94 78 94 77 / 30 10 10 0

BRO WATCHES/WARNINGS/ADVISORIES

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