Eric Berger

In brief: All our available data continues to point toward the arrival of a line of storms after midnight, moving from west to east across the Houston metro area. Because the heaviest of these rains are likely to fall north of Houston, and the high amounts of rainfall already received there this week, we are raising our flood alert for areas along and north of Interstate 10 to Stage 2 for tonight and Sunday.

The overall pattern we’ve been in for the last several days will persist tonight into Sunday. That is to say, the atmosphere is chock full of moisture and unstable. A forcing agent will come early Sunday as a disturbance moves into the region from the west. In recent days the trend has been toward rain events over-performing expectations. So I don’t want anyone to let their guard down just yet.

After midnight we’re likely to see the development of an MCS to the west of Houston. What is an MCS? In meteorological parlance, it stands for ‘mesoscale convective system,’ essentially a large complex of thunderstorms. But when they come through at night I prefer to think of an MCS as a ‘midnight canine stimulant.’ So yeah, it could be one of those nights.

The primary risk is thunderstorms and heavy rainfall. Generally, I think most of the area will pick up 1 to 3 inches, but my concern is the potential for bullseyes of 5 inches, or more. The most probable location for these heavy rains is areas north of Houston, which have already received a foot of rainfall, or more, during the past week.

After the strongest part of the MCS sweeps through, likely around 3 to 6 am for areas such as Katy, 4 to 7 am for downtown Houston, and a little later for the coast, we are likely to see additional showers—on and off—for most of the rest of Sunday. It’s my hope that these will be a little less intense, and a little less organized than the initial push early on Sunday. Matt will have a full update for you tomorrow morning.

You’re probably not going to be believe me, and that’s fine. But I still do expect our pattern to dry out on Monday. We’ll turn sunnier, and hotter for awhile. Rain chances may not go away entirely, but they’ll be significantly diminished.

In brief: An unexpectedly intense flooding event has engulfed areas north of Houston this week. We discuss that, and the ongoing forecast for the weekend, which could see an additional round of storms on Sunday before things start to dry out next week.

If you live south of Interstate 10, you may be wondering what the fuss is all about in regards to heavy rains this week. Much of this area has received 2 inches or less over the last five days, and certainly not experienced anything remotely close to flooding conditions. However, looking at the rainfall accumulation map below, we can see that eastern Montgomery County got rocked with 12 inches of rain, and further to the north, Walker and San Jacinto counties recorded 15 to 20 inches of rainfall. Some of this came very quickly, with high rainfall rates.

And so we have a situation where much of the region is just fine, but there is terrible flooding ongoing along the San Jacinto and Trinity river basins. The most dangerous flooding is occurring along the East Fork of the Jacinto River, but the entire north and northeastern parts of the Houston metro area are dealing with significant and ongoing flooding.

What’s next

So what happens next? After today’s showers, we should see a reprieve for the rest of this afternoon and evening. Our record for predictions this week has been pretty shoddy, but at this point I only expect development of sporadic showers on Saturday morning. And most of Saturday, frankly, looks mostly rain free. At this time I think we’re unlikely to see more than scattered showers and thunderstorms, with accumulations not amounting to much.

Unfortunately, it does appear as though a final storm system will work its way toward the area later on Saturday night, or Sunday morning. This atmospheric disturbance will likely bring widespread showers and thunderstorms on Sunday morning-ish, and perhaps throughout much of the day. As a rough guess we’re looking at additional accumulations of 1 to 3 inches, with the potential for higher totals. This will, unfortunately, only exacerbate ongoing river flooding.

By Sunday night high pressure really should begin to assert itself, and most of next week looks sunnier, and hotter. Rain chances look lower for most of the week, although perhaps not zero.

Given the unpredictability of the storms we’ve seen this week, and the threat of additional rain on Sunday, we’re going to continue with posts each morning this weekend to keep you updated. Thanks as always for reading, and for your patience as we have struggled to grapple with a challenging forecast that has been more miss than hit.

In brief: The heavy rainfall has exited the Houston area, for now at least. The thunderstorms dropped 1 to 3 inches of rain across the southern half of the region, but some whopping totals of up to 8 inches near locations such as Spring and Kingwood during a few hours today. We may see some additional rains tonight and on Friday, but we are confident that the worst is over.

As of about 4:30 pm this afternoon, the mass of showers and thunderstorms that brought widespread rain to Houston today has exited to the east. The atmosphere is now pretty worked over, so we should see fairly calm conditions for the rest of this afternoon and evening. And after that? There is the possibility of scattered showers and thunderstorms returning after midnight, especially for areas south of Interstate 10. Overall these areas have not been particularly hard hit, so I’m not particularly concerned about these storms in terms of flooding. Because the worst is likely over, we are stepping back our flood alert to Stage 1.

We may see another round of showers develop during the morning hours on Friday and persist into the afternoon. Given the messy forecast today, I’m not particularly confident in anything tomorrow. However I don’t anticipate it being nearly so potent as the system we saw today. Matt will have all the details first thing on Friday morning, when we should have the forecast better in hand.

The big story now is river flooding due to the incredible amounts of rain that fell north of Houston this week, including Wednesday night. Lakes Conroe and Livingston were particularly inundated. The National Weather Service has a map where you can find detailed flooding forecasts for various rivers in the greater Southeast Texas area here.

River flooding

Among the biggest concerns are the East and West Forks of the San Jacinto River. Already a mandatory evacuation is in effect for the eastern side of the river, from FM 1485 to Lake Houston. According to Jeff Lindner of the Harris County Flood Control District, forecasted water levels on the East Fork will rise 7 to 8 feet higher than earlier this week. Structures on the ground will be flooded to rooftops levels. Elevated structures will be flooded. For reference, the forecasted water level is only 3 feet below those of Hurricane Harvey.

Conditions are also serious along the West Fork of the river. Lindner says the river is rapidly rising from upstream inflows, and will rise to near 62 feet on Saturday. Widespread low land flooding will occur impacting the following subdivisions: Belleau Woods, Rivercrest, Northshore, Forest Cove, Kings Point, and Atascocita Shores. Flooding of streets in Kingwood, as well as lower structures near the river will also be possible.

If you live in flood-affected areas please do not drive into high water.

In brief: Due to the unanticipated escalation in storm activity this morning, it now appears as though the city of Houston will see intense showers and thunderstorms during the next several hours, through Thursday afternoon. We are issuing a Stage 2 flood alert for the entire area due to the high rainfall rates and timing of street flooding.

We were wrong. Just hours ago, in this morning’s post, it looked as though a band of showers north of the region would slowly wane through the morning hours. However, as we’ve been monitoring radar trends, that clearly has not happened. Instead we’ve seen this band thicken and slowly progress southward toward central Houston. Already in locations such as Spring, Humble, and Atascocita have picked up in excess of 5 inches in just a couple of hours this morning. That is a lot of water in a little time.

Although there remains considerable uncertainty, it now appears as though this line of storms will continue to sag southward this morning before reaching the coast by late afternoon. It is likely to have significant impacts in the city of Houston and surrounding areas, including street flooding. Of particular immediate concern is the high rainfall rates associated with these storms, which will back roads up quickly. For this reason we are escalating to a Stage 2 flood alert for the entire region. Conditions should hopefully improve late this afternoon or evening.

All of this activity should have an impact on the atmosphere, and because of this it no longer appears as though the region will see a round of stronger storms overnight, into Friday morning. But given the unpredictability of this system so far, that is not an entirely confident prediction.

Please stay safe today and do not drive into high water.