San Antonio faces more flash flooding as rain continues to pour

Update: 5:44 p.m. Wednesday, January 24: According to an updated situation report by the National Weather Service, the San Antonio area is now expected to see heavier rain activity prolonged in central counties. Residents can expect a potential 1 to 2 inches of rain over the expanded watch area.

The original story as follows:

We’re almost through the worst of it, San Antonio. It’s been a very wet week so far, but things are about to calm down and dry up. Don’t chuck those umbrellas in the back of your closet just yet, though, as we are expected to see another round of showers overnight headed into Thursday morning, January 25.

It’s been hectic, we know. With roads constantly being closed and people being swept away in rapidly rising waters, this rain, while much needed to replenish aquifers after what’s been an exceptional drought, has really plagued the Alamo City. You just need to hold out for one more day, San Antonio, as the National Weather Service warns that already saturated grounds could lead to more flash flooding as another .5 to 1 inch of rain is slated to hit the city Wednesday night headed into Thursday morning.

“Saturated just means the ground’s not able to absorb as much rain as quickly as it used to. So, think of it like a sponge. When you have a dry sponge, it’s going to be able to absorb a lot of water fairly quickly. But once it’s completely wet, it’s not going to absorb a lot of water,” Christopher Morris, senior service hydrologist with the National Weather Service, told MySA. “So, in that sense of rainfall and runoff, as you have more rainfall, the sponge can’t soak up any more water.”

This saturation of local soils – or the metaphorical sponge – means even mild rains and thunderstorms, like the storms expected Wednesday night, could lead to flash flooding events in areas prone to flooding. Morris said the typical culprits are at play amid flood warnings, including where Leon Creek meets Highway 90 and where Salado Creek meets I-35. These two areas are examples of many low-lying areas that have seen flooding over the past several days. So, brace yourselves for another round of dozens of road closures Thursday morning as water levels rise.

It’s been a long time since we’ve seen creeks and rivers flowing at the level they are currently. Really, may creeks had dried up after a long-lasting and record-setting drought plagued much of South Central Texas over the past year. However, Morris said several creeks and rivers are starting to see increased flow thanks to all this wet weather, and it means flooding can happen without much rain.

“It’s been a while since we’ve seen decent rainfall. So, a lot of streams around the area either dried up or were barely flowing,” Morris said. “Now, since the rainfall, we’re seeing a lot of those responding. Now, thankfully they’ve not risen quite as high as they could potentially. But they are staying in what we call action to minor flood stage. So, that means that pretty much the stream is full of water and maybe breaking the banks of the river just a little bit. But there certainly has been historically more flooding that what we’re seeing now.”

While watersheds may not be reaching record heights in terms of water level or stream flows, it’s been quite the rainy month for San Antonio – a promise finally fulfilled after forecasters said the persisting El Nino weather pattern would bring a wetter than normal season this winter. In fact, Morris says San Antonio saw 4.9 inches of rain this week as of Wednesday morning. For context, San Antonio typically sees less than 2 inches of rain in the entire month of January. In just a week, rain totals have more than doubled the average, and more rain is on the way.

“A final round of showers and storms will cross the region from west to east overnight,” the National Weather Service San Antonio-Austin office tweeted Wednesday afternoon. “Some areas may also see redeveloping fog. Flood watch remains in effect through noon tomorrow, with another 1-2 inches possible over saturated ground. Isolated severe hail/winds possible south.”

With South Central Texas receiving so much rainfall in a short span and roads consistently being overtaken by flowing creeks and rivers, the message from the National Weather Service has been strong and consistent: Wherever you’re going isn’t worth your life. Turn around, don’t drown.

“So, the main thing to keep in mind is the grounds are saturated. Any extra rainfall will quickly fill up those creeks and streams and those low spots on roadways. Just like we’ve said the past couple warnings, do not try to cross a road that is flooded because most of our flood fatalities around here are vehicles – people trying to dive through flooded roadways,” Morris said. “We’ve had a few swift water rescues over the past couple days. So, again, if you come up on a flooded roadway, don’t try to cross it. It’s not worth your vehicle and/or your life. Just find another route.”