Storm chances rising in South Texas Monday, flooding is possible

South Texas is finally seeing some rainfall that could make a difference in the current drought.

From Saturday night through Sunday, 0.99 inch of rain was recorded at San Antonio International Airport – the highest 2-day rainfall total the city has received in nearly six months, since 1.19 inches was recorded on Oct. 24-25.

And there’s more where that came from. Weather models indicate that another round of potentially heavy rain will be possible Monday across South Texas, as an atmospheric disturbance moves northward from the Rio Grande.

While the incoming rainfall is likely to be beneficial for much of drought-stricken South Texas, a few spots could experience isolated flooding. Here’s a breakdown of what to expect. 

Scattered showers and storms are expected to develop across parts of South and Central Texas starting early Monday morning. If you have to be out on the roads, be sure to take it slow and allow for extra time to get to your destination. Rain chances in San Antonio will be near 40% at 7 a.m., and chances will increase slightly by the mid- to late morning.

Rainfall is not expected to be consistent throughout the entire day. Instead, San Antonio will likely see off-and-on periods of moderate rainfall.

Thankfully, the risk of severe thunderstorms – which includes large hail and damaging winds – is quite low. That said, many storms will still produce thunder and lightning, as well as occasional heavy downpours.

The most widespread rainfall is expected to arrive from the mid-afternoon through the evening, especially between the hours of 3 and 9 p.m. During this time, San Antonio rain chances will likely reach 60 to 80%, and rainfall could last for hours at a time. Rainfall will likely affect the Texas Cavaliers River Parade, which starts at 7 p.m. in downtown San Antonio.

Temperatures on Monday will be very cool. Morning low temperatures in the mid-50s are expected to rise only into the low 60s by the afternoon – about 20 degrees below average for this time of the year.

Yet another round of scattered showers and thunderstorms will be possible early Tuesday morning and into the afternoon. Once again, heavy rain will be possible, but the risk of hail will stay low. 

How much rain? The National Blend of Models suggests that the San Antonio area could see 1-2 inches of rainfall through Tuesday. However, isolated higher totals of 3 to 4 inches or more are not out of the question from the Hill Country and into parts of the Interstate 35 corridor.

For most, flooding is not expected to be a widespread issue. However, it’s difficult to pinpoint exactly where those isolated higher rainfall totals will occur. For the spots that do see 3 inches or more of rainfall, flooding will be a possibility. 

The National Weather Service has placed San Antonio and the surrounding areas under a Level 1 of 4 risk of excessive rainfall. That means isolated flooding is possible across the region, but widespread flooding is not expected.

Rain chances will start to decrease by the second part of the day Tuesday. Still, temperatures will stay well below average, as highs rise only into the upper 60s to low 70s.

By Wednesday, southerly winds will transport warmer air back into the region, allowing high temperatures to rise back into the low 80s. A few lingering showers and storms will be possible, but rain chances will fall to 20-30%.

Thursday and Friday will bring even warmer weather, as high temperatures are expected to reach 85 to 87 degrees. An isolated, pop-up thunderstorm is possible, but rain chances will be only around 20%.