Eric Berger

After an ugly round of storms moved through Houston on Thursday night and Friday morning, the region has seen some general clearing today. This is good because several waterways, including Clear Creek in the southeastern part of the metro area, crested above their banks this morning and need some time to recede. Alas, this multi-day rainfall event is not quite over.

Based upon the stability of the atmosphere, we can reasonably expect a mostly quiet evening and probably most of Friday night before storms return to the region on Saturday. There’s not a ton of agreement among the models, but generally we think most of the action will probably be between I-69 and the coast, over Brazoria, southeastern Harris, and Galveston, Chambers, and Liberty counties. (Our concern is that this is where the aforementioned Clear Creek lies). For most of this area, beginning around sunrise or a few hours later, we expect perhaps 1 to 3 inches of rain. That’s not overly concerning, but we can’t rule out a few isolated areas with 4 to 5 inches. For central and northern parts of the region, we expect lesser amounts of rainfall, with perhaps 0.5 to 2 inches of rain. The good news is that none of the forecast models are predicting some of the extreme, 3+ inches per hour rates we’ve seen earlier this week that rapidly led to street flooding.

We will see some thunderstorms with Saturday’s rainfall, but at this time we do not anticipate the kinds of widespread, severe thunderstorms, with hail and rampaging winds, that the region experienced Thursday night. And the storms should mostly develop after sunrise, so hopefully we can all get a good night’s sleep for a change.

Depending on which model you choose, rains should end from west to east, sometime between noon and early Saturday evening. We still expect drier air, with lower dewpoints and sunshine on Sunday, all of which should help begin to dry out the area.

We have seen very heavy rainfall develop along and northwest of Interstate 69 this evening. Areas near the Addicks and Barker reservoirs have been especially hard hit, some of which have received 5 inches of rain since 6-9pm. Water levels in the reservoirs are rising, but still well below flood level as of 8:45pm CT. With flood warnings issued, and street flooding occurring across much of west, northwest, and north Houston this evening, travel should cease for the night. It is time to hunker down.

As for the rest of the night, we expect this mass of rains to the northwest of I-69 to hold together until around 10pm or 11pm, after which time it should begin to sag slowly to the southeast. After this time we expect most of the action to occur more close to the coast, on the southeastern side of I-69. In addition to this sagging mass of showers, another complex of storms will move up from South Texas, likely reinforcing the already existing coastal showers.

Given the totals we’ve seen so far, widespread totals of 4 to 8 inches seem possible for areas northwest of Houston tonight, with higher isolated totals. Elsewhere, totals are likely to be closer to 1 to 4 inches of rain, with isolated areas of 8 inches possible later tonight.

In addition to the heavy rains, we are seeing reports of hail, up to 2 inches in diameter, across much of the area. This will continue for the next couple of hours, and we may also see the potential for damaging straight-line winds later tonight. An unpleasant night, for sure.

Storms will eventually exit to the east, with rains likely ending across the area from 6 to 10am on Friday morning, from west to east. Then we can probably expect another wet night Friday night, although hopefully not as extreme.

In this morning’s post, I wrote that there was the “potential” for storms and heavy rainfall today, but we didn’t have any confidence in whether it would materialize or not. Fortunately, so far the storms have not materialized.

Our biggest concern today has been a broad line of showers and thunderstorms moving eastward across central Texas today, associated with a cold front. High resolution modeling suggested this line would weaken as it approached the Houston area, and in fact that is what has happened, which is good for Houston. See the comparison below of radar images from earlier this afternoon.

As this broken line of showers and thunderstorms moves into the Houston area this afternoon and evening, the most likely outcome is that the system does not get too organized over the city. The best chance of storms will probably come to the north and east of Bush Intercontinental Airport, and the good news is that the storms seem to be holding a fairly steady eastward motion which should help to limit storm totals. As a result I think most of the area will probably see less than 0.5 inches of rain later today and tonight, with a few unfortunate pockets perhaps picking up a quick 1 to 3 inches.

We expect a fairly calm start to Thursday, before more showers later Thursday into Friday morning, and then yet another round from Friday night into Saturday morning. We’ll have full coverage of that tomorrow morning.

By several measures, Tuesday’s rains were exceptional for parts of the Houston metro area. According to the Harris County Flood Control District, one gauge in Sugar Land recorded 5.16 inches of rainfall in 1 hour and 15 minutes, and multiple other parts of the city saw rainfall rates nearly that extreme, which will quickly overwhelm the capacity of urban roadways. Tuesday’s commute was an absolute mess. Moreover, unofficially, an estimated 400 homes flooded in Kingwood. The Brazos River at Richmond has already reached a minor flood stage. Because of the unexpected intensity of Tuesday’s precipitation, and the potential for more heavy rainfall over the next four days, we are raising the expected impacts from these storms to Stage 3 (out of five levels) on our new flood scale.

Fortunately, the storms finally died down between 9pm and midnight on Tuesday, allowing the area a reprieve during the overnight hours. This allowed several creeks and bayous near the tops of their banks to begin receding, although many remain higher than normal. So let’s discuss what happens next.

Wednesday

The unstable, very moist atmosphere that produced widespread heavy rainfall on Tuesday more or less remains in place today, and this should fuel at least some scattered showers and thunderstorms throughout the daytime in the city. We do not believe these storms will be as widespread as on Tuesday, but certainly with some of the more slow-moving systems some areas could pick up a quick 1 to 3 inches of rainfall. Overall, however, most of the city will probably receive less than 1 inch of rain today.

Our other concern stems from an upper-level disturbance and cold front now bringing storms to west and central Texas. This should move toward the region this afternoon and evening, bringing with it the potential for severe thunderstorms toward Houston. While most of the action will probably remain north of Houston, NOAA’s storm prediction center has brought the region where there is a “slight” chance of damaging winds, hail, and potentially tornadoes down to about the Interstate 10 corridor. This will be worth tracking.

Basically, today is a day of “potential.” The unstable atmosphere could produce a very wet day, almost like Tuesday for some areas. Or showers could be much more scattered in nature—our high resolution models have performed so poorly of late it’s just hard to say for sure. Similarly, the upper-level disturbance could remain far enough north of the metro area such that it will not cause major problems—or not. We’ll be monitoring throughout the day for you.

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