The National Weather Service kept much of South Texas under a flood watch early Monday, Nov. 9, after radar estimates showed 4 to 8 inches of rain across a broad stretch of the southern Rio Grande Plains and Brush Country. Forecasters in Corpus Christi said another 1 to 3 inches could fall through Monday evening, with isolated totals above 4 inches. The watch extended to noon Central time and covered parts of the region from Laredo to the Coastal Bend.

Federal forecasters also warned of possible renewed flooding where storms crossed areas that received heavy rain Sunday. Near Corpus Christi, a separate river warning called for Oso Creek to rise above flood stage Monday morning and crest late that night. The rainfall estimates describe what radar indicated had already fallen in one part of the region; the creek crest and the additional rain were forecasts.

Why the next round of rain matters

The Weather Prediction Center said in its overnight discussion that scattered showers and thunderstorms had been expanding ahead of a disturbance moving toward the Rio Grande Valley from northeastern Mexico. Individual storms were moving northeast, but new showers could form behind them and follow a similar path. That pattern can put several bursts of rain over the same community even when no individual storm stays in place for long.

The center expected some storms to produce more than an inch in an hour early Monday. It said rates above 2 inches an hour were possible near the lower Texas coast if showers repeatedly formed, particularly along and east of U.S. 77 south of the Corpus Christi area. The regional watch identified urban areas, places with poor drainage and low-water crossings as vulnerable. Those are local risks within a broad watch area, and the forecast does not imply that every community will get the same amount of rain.

Oso Creek faces a later crest

The river warning illustrates why flood risk can persist beyond the heaviest downpour. The weather service reported a reading of 11.1 feet on Oso Creek at 7:15 p.m. Central time Sunday. In its Sunday evening warning, it projected a crest near 23 feet late Monday night, above the creek’s 20-foot flood stage. The warning described that as moderate flooding and said the creek could fall below flood stage late Tuesday night. Those figures are water levels at the gauge, rather than depths across nearby properties.

At 20 feet, the weather service says lowlands from the vicinity of Violet Road to Oso Bay can flood, along with secondary roads and low bridges near the creek. The warning period extended from Monday morning to Wednesday afternoon, beyond the projected crest. The noon end time on the broader rainfall watch therefore gives no indication of when a creek crossing will reopen or when water will leave low ground.

Conditions differ from the border to San Antonio

Overnight forecasters issued a more localized flood advisory for south-central Webb County, including the Laredo area, after radar indicated heavy rain. The advisory said minor flooding was ongoing or expected to begin shortly in low spots and places that drain poorly. At 4:08 a.m. Central time, the same office issued a separate advisory for parts of Bee and Live Oak counties. It estimated that 1 to 2 inches had already fallen there and forecast another half-inch to an inch, enough to cause minor flooding in poor drainage areas. A local advisory describes the expected impact in a particular area; the regional watch covers a larger area where conditions can produce flooding, even if some places see little or none.

Farther north, the Express-News projected about half an inch to an inch of additional rain Monday in San Antonio, for a two-day total of roughly 1.5 to 2.5 inches. Its forecast called for higher totals to the south and west, including around Pearsall, Carrizo Springs, Eagle Pass and Laredo. Those differences help explain why a citywide rainfall figure from San Antonio cannot stand in for conditions along the border or near the coast.

What Texas has put in place

Gov. Greg Abbott directed the state on Friday to make additional emergency resources available ahead of the rain, as ABC News reported Sunday. The state inventory included rescue boat crews and high-clearance vehicles, state transportation personnel to monitor roads, and emergency medical teams with ambulances. Texas Parks and Wildlife and the Department of Public Safety also listed helicopters capable of lifting people from floodwaters. The announcement described resources available to support local officials; it did not establish that every team was deployed or that rescues had occurred in the overnight advisory areas.

The next checks for local officials are where new rain overlaps the areas that were already soaked and whether Oso Creek rises as forecast. The weather service warned drivers to avoid flooded roads and follow barricades, including after rain eases. The state directs residents to official resources for road conditions and local instructions. Conditions can change at a single crossing even as the broader flood threat diminishes.