More Locally Heavy Rainfall and Potential Flooding Through At Least Saturday
Additional heavy rainfall overnight Tuesday caused more flooding in central Hidalgo County, near Falfurrias, and in pockets between Bayview and Arroyo City in Cameron.
Total rainfall for this event so far ranges from 6 to 12 inches in much of Hidalgo and Brooks County, 3 to 6 inches across the Rio Grande Plains, and 3 to 7 inches across Kenedy County ranches. 1 to 3 inches fell elsewhere, except 4 to 7 inches in a band from Bayview to Arroyo City in Cameron County.
In some areas, rainfall in just four days has doubled the September average.
More rain is on the way. No matter what happens with the tropical disturbance, deep atmospheric moisture will be maintained through at least Saturday.
The disturbed area is now in the southwest Gulf, approximately 450 miles east-southeast of South Padre Island. It remains disorganized, but remains likely to become a tropical depression on Thursday.
Whether the system develops or not, primary threats to the region remain:
Locally heavy rainfall and flooding
Building surf, dangerous rip currents, and tidal run-up toward the dunes (beaches)
Given the wet forecast, remaining drought/dryness will likely be erased by next week
Heaviest additional rains may fall in the Rio Grande Plains, including Zapata County but favoring locations along the river to the north. This would ensure additional welcome rises in Falcon Reservoir and help irrigation and water use needs into next winter and beyond.
What to Watch For
Through Saturday, an additional 1.5 to 2.5 inches of rain is likely area wide. However, local bands or clusters tonight (lower RGV) Thursday (anywhere, favoring the lower/mid Valley), and Friday-Saturday (anywhere, starting to favor the Rio Grande Plains) could produce 5+ inches
These rains falling on already saturated ground would leave 2 to 3 feet of high standing water in poor drainage or already high water locations.
Location means everything. An additional 5+ inches in central Hidalgo will put more stress on the interconnected drainage system, requiring continued/expanded pumping operations.
Should the system form and intensify more than currently expected, heaviest rainfall would "tighten" toward the center and favor locations along/north of the track, which could reduce totals in the populated RGV...
...but that same tightening would increase rainfall/flooding in the Rio Grande Plains, which could touch Zapata and Hebbronville late Friday and Saturday
Arroyo Colorado and Los Olmos Creek (Falfurrias area) continue to run high. Additional heavy rains in central-eastern Hidalgo would cause another "wave" down Arroyo Colorado anytime Thursday through Saturday; should a consolidated heavy rain area form across the Coastal Bend through the South Texas Brush Country, Los Olmos Creek would exceed flood stage at minor, with moderate levels a reasonable worse case scenario.
Increasing easterly fetch will bring dangerous rip currents Thursday and Friday, with residual currents into Saturday
Surf waves are likely to build to 3 to 5 feet, locally 6 feet, Thursday afternoon through Friday
Tidal run-up may reach the duneline at high tide Thursday night and Friday night
Swells will build the sea heights to 5-6 feet or higher. More development than expected could bring 8+ feet as a reasonable worse case, along with sustained winds gusting to Gale force in squalls.
Potential Impacts/Recommended Actions
Residents in flood prone areas where water could reach the base of their home should consider sand bags. Note, however, that sandbags will not prevent floodwaters at higher levels than a few inches at the door.
Have an outdoor activity? Have a rain plan.
Continue to use smart driving decisions in heavy rainfall, especially at night. Plan an alternate route now to avoid putting yourself and your vehicle in danger. Frontage roads and low-lying roads in poor drainage locations have flooded with this event, but a longer, safer commute is much better than one where you may need to be rescued!
Boaters/fishers with small craft should strongly consider postponing trips until further notice (due to the combination of storminess, waves, swells, and wind gusts)
Poor to average beach swimmer should stay in water at waist deep or lower.