Heavy rains and thunderstorms made for a loud night across the Upper Texas Coast and into portions of Southeast Texas. As we’ve been saying for a few days the eventual track of the low pressure would dictate who ended up dealing with the heaviest rains. The low ended up tracking over western Harris county early this morning. That kept the heaviest rains mostly south and east of Houston-proper. Freeport up to Galveston to Winnie has dealt with a particularly intense feeder band overnight.
— Jeff Lindner (@JeffLindner1) September 18, 2019
We were lucky that the weather had been dry as of late. Soils were able to absorb several inches of rainfall without issue. However, we’re seeing more of that rain runoff into drainage systems now that soils have become saturated. The story will be the same for those upstream who will face the chance of heavy rainfall later today, tonight, and into the day Thursday.
Here is the latest three-day precipitation forecast from the Weather Prediction Center. This runs from 7 AM this morning through Friday. Keep in mind these are on top of what already fell overnight across the Upper Texas Coast into Southeast Texas. We did see another nudge to the east with the heaviest rain axis based on the overnight forecast data.
With such a slow-moving area of low pressure, the smallest wobbles can make the difference between a town receiving flooding rains or just an inch or two of rain. There is a sharp rainfall gradient along and west of the low’s track – known as the ‘clean’ or ‘dry’ side of the system. Even though the low will slowly move northward away from Southeast Texas by tonight it looks like we could still see feeder bands ‘reach’ out into the Gulf of Mexico. Those would likely produce quite a bit of rainfall and thus present additional flooding concerns for the Upper Texas Coast and Southeast Texas tonight into Thursday.
My concern is definitely increasing regarding a significant flooding threat tonight into Thursday morning along and east of Interstate 45 across East Texas into Far Southeast Texas. Some weather model data suggests an intense area of rainfall will develop tonight and essentially sit for several hours. That scenario would result in five to ten inches of rain falling within a three to six-hour span. There could even be rainfall amounts higher than that if the ‘worst-case scenario’ developed. I should be able to provide a more accurate answer to that uncertainty by the late afternoon.
Luckily it has been dry as of late so soils will be able to absorb the initial rainfall. Still, if we have rainfall rates of three to five inches per hour, it will not take long for flash flooding to develop. I have a particular fear of flooded roadways across East Texas overnight that may be difficult to see due to darkness.
So the forecast itself will hinge on the slow-moving speed of the low pressure as it moves north over the next two days. We’ll see the heaviest rainfall during the overnight hours on the east and southeast side of the low. Training storms (storms which keep redeveloping and moving over the same areas) are a big problem during the overnight hours too. That’s how we can see extreme rainfall amounts in just a few hours. During the day we tend to see more storms farther out from the low – and those can also produce heavy rainfall. This cycle will continue again tonight, into Thursday, and potentially into Thursday Night. We’ll be riding the system by Friday Night – just as an upper-level storm system enters the Panhandle and Oklahoma.
I’m going to try and get a few hours of shut-eye this morning. You can keep tabs on the radar with our free HD interactive weather radar here on our website and in our free mobile app.