Marine Weather and Tide Forecast for Port Isabel, TX

DISCUSSION
Issued at 151 PM CDT Sun Mar 15 2026

The main focus of the forecast for Deep South Texas and the Rio Grande Valley continues to be the wind, fire, coastal and marine hazards resulting from a strong cold front moving through tonight.
This front extends from a rapidly intensifying low pressure system currently over the Midwest, ahead of a deepening trough over the Central Plains. Lowering pressure heights over the Southern Plains and the Sierra Madre interacting with a surface high pressure over the Gulf have already led to gusty winds, occasionally gusting to 45 mph, and higher, over the Lower RGV, this morning and early afternoon. As the low departs further east into the remainder of this afternoon, northwesterly to westerly lower level winds on the low's backside will continue to progress a dry line into the region, bringing lower relative humidity. Meanwhile, the pressure gradient is anticipated to loosen due to rising heights, gradually reducing winds across the CWA into this evening as the dry line progresses eastward to possibly as far east as inland Kenedy County and the western portions of the Lower RGV. Due to the narrow window of breezy conditions coinciding with lower relative humidity, have held off on issuing a Fire Danger Statement (RFD) for this afternoon. However, it is highly urged to refrain from outdoor burning as the region remains within a D2 to D4 (Severe to Exceptional) Drought with abundant cured fuels; stronger gusts could quickly spread wildfires. Moisture pooling east of the dry line and enhancing lift ahead of the front may produce isolated showers and thunderstorms late tonight across the Lower RGV to the coast, where there is a (15-30%) of rain, with the best chance along the coast.

Another byproduct of the dry line is the compressional heating of the lower atmosphere, likely leading to near-record to record- breaking heat this afternoon as temperatures soar 10-20 degrees above average, reaching as high as the upper 90s to lower 100s across most inland areas.

Now onto the biggest focus: the fire and coastal hazards associated with the fierce northerly winds and significantly drier air ushered southward into the CWA by the strong cold front expected to enter the Northern Ranchlands and the Rio Grande Plains potentially between 9-11 PM tonight and pass through the entire region by the pre-dawn hours tomorrow morning; strong northerly winds of 20-30 mph, with gusts to at least 45 mph are expected region-wide. Have increased wind and wind gust speeds west of US-281 and added a Wind Advisory for Jim Hogg, Starr and Zapata counties from 10 PM tonight until 8 AM tomorrow morning, where the majority of CAM models have consistently agreed with the latest HRRR probabilistic guidance, which suggests a medium to high chance of gusts up to 55 mph, or higher, for several hours following the front. Another Wind Advisory is in effect for all counties further east from 10 PM tonight until 1 PM tomorrow evening as gusts up to 45 mph, or higher, could persist into the early afternoon hours, especially along and near the immediate coast. As much drier air is advected southward via the strong northerly winds, the combination of very low relative humidity and breezy to windy conditions will lead to critical fire weather conditions and a Red Flag Warning remains in effect across all of Deep South Texas, with the exception of the barrier islands, from 10 PM tonight to 7 PM tomorrow evening.
See the FIRE WEATHER section below for more details. Meanwhile, at the coast, the strong winds will result in dangerous surf and life threatening rip currents. A High Surf Advisory and a Rip Current Statement are in effect from 7 AM to 7 PM tomorrow.
Hazardous surf, dangerous rip currents and minor coastal flooding are likely to continue into the beginning of this week.

Otherwise, winds continue to diminish throughout tomorrow night.
Cold air advection behind the front results in below average temperatures through Tuesday with highs only reaching into the 60s on Monday, which is nearly a 30-35 degree drop from this afternoon's highs. Overnight lows fall to the 40s/50s tomorrow night, with low 40s likely across the Northern Ranchlands. Average temperatures are expected Wednesday as winds become southeasterly and then above average by Thursday. Breezy and dry conditions continue through next weekend, keeping fire weather concerns elevated.

AVIATION
(00Z TAFS)
Issued at 622 PM CDT Sun Mar 15 2026

Through 00z Tuesday....The main weather concern to aviation ops for the terminals through the forecast period will be the strong to potentially damaging northerly winds developing later tonight into Monday, which will likely have major impacts/implications particularly to east to west oriented runways.

VFR conditions, by and large, will prevail through the 00z TAF cycle.
There could be a few MVFR-LIFR clouds at times, particularly tonight.

Ahead of an approaching cold front, winds will continue out of the south with speeds between 7-15 kts, occasionally gusting as high as 20 kts through the evening hours before fading. In response to the cold fropa later this tonight, winds will shift out of the north and become strong with speeds between 15-25 kts. Winds will gusts generally between 35-45 kts, however, there could be isolated gusts as high as 50 kts or so on Monday.

MARINE
Issued at 151 PM CDT Sun Mar 15 2026

A tightened pressure gradient continues to result in strong southerly winds and moderate (3-5 feet) seas this afternoon, gradually decreasing to fresh to strong throughout the later afternoon and early evening hours as the gradient loosens. A Small Craft Advisory remains in effect until 10 PM this evening. In the hours leading up to the arrival of the strong cold front late this evening, there is a low to medium (20-50%) chance of rain as isolated to scattered showers and thunderstorms develop. Following, the front passes through, quickly resulting in gale force northerly winds and very rough seas, continuing through tomorrow morning, with gale force gusts persisting through tomorrow afternoon. A Gale Warning goes into effect across all Lower Texas coastal waters from 10 PM tonight until 7 PM tomorrow evening. Small Craft Advisory and/or Small Craft Exercise Caution headlines are likely tomorrow night into Tuesday as winds and seas gradually improve. Gentle to moderate southeasterly to southerly winds and moderate seas return by Wednesday morning, continuing with dry conditions into the remainder of this week.

FIRE WEATHER
Issued at 151 PM CDT Sun Mar 15 2026

A Red Flag Warning remains in effect for all of Deep South Texas, with the exception of the barrier islands, from 10 PM tonight until 7 PM tomorrow evening. Strong northerly winds and rapidly crashing relative humidity values along and behind a strong cold front arriving late this evening will lead to elevated to critical fire weather conditions through tomorrow afternoon. Northerly 20 foot winds of 20 to 30 mph, gusting as high as 35 to 45 mph or higher, and minimum relative humidity values as low as 10-35 percent are likely, with the lowest relative humidity along/west of US-281. As cured fuels remain abundant within the ongoing D2 to D4 (Severe to Exceptional) Drought across the region, it is strongly recommended to refrain from outdoor burning.

PRELIMINARY POINT TEMPS/POPS
BROWNSVILLE 59 64 53 72 / 20 0 10 10 HARLINGEN 52 66 47 72 / 10 0 0 0 MCALLEN 55 68 49 76 / 10 0 0 0 RIO GRANDE CITY 52 68 47 75 / 0 0 0 0 SOUTH PADRE ISLAND 59 62 58 67 / 20 10 10 10 BAYVIEW/PORT ISABEL 56 63 53 70 / 20 0 0 10

BRO WATCHES/WARNINGS/ADVISORIES
TX...Red Flag Warning from 10 PM this evening to 7 PM CDT Monday for TXZ248>255-351-353>355.

Wind Advisory from 10 PM this evening to 8 AM CDT Monday for TXZ248-249-252.

Wind Advisory from 10 PM this evening to 1 PM CDT Monday for TXZ250-251-253>255-351-353>355-451-454-455.

High Rip Current Risk from Monday morning through Monday evening for TXZ451-454-455.

High Surf Advisory from 7 AM to 7 PM CDT Monday for TXZ451-454- 455.

GM...Small Craft Advisory until 10 PM CDT this evening for GMZ130-132- 135-150-155-170-175.

Gale Warning from 10 PM this evening to 7 PM CDT Monday for GMZ130-132-135-150-155-170-175.