In brief: Well, it’s over. In today’s post we discuss last week’s extraordinary precipitation event that finally ended Sunday, and some lessons learned. Houston faces calmer weather this week, with two frontal boundaries coming later this week and over the weekend to bring some drier and slightly cooler air into the region. Unfortunately it does appear as we’ll see some decent rain chances on Mother’s Day.

A week of rains

The map above shows rainfall totals over the last week, and for locations north of Interstate 10 they’re pretty incredible. Some locations in Walker and San Jacinto counties recorded in excess of 25 inches of rainfall, and closer to Houston eastern Montgomery County picked up 15 inches of rainfall. The southern half of the region, by contrast, saw significantly less rainfall.

Matt and I have taken away a couple of lessons from this. First of all, it’s a reminder of the unpredictability of these kinds of rain events, where you have slow-moving boundaries that are able to tap into ample moisture from the Gulf of Mexico. These springtime rains are among the hardest to predict. To wit, as late as last Tuesday we were calling for 0.25 to 2 inches of rainfall for the week, and saying, “These are likely to be garden-variety showers rather than anything too intense or organized.” Obviously that was a huge, humbling miss. We weren’t alone in that miss, and no one was predicting what ultimately happened. But it’s safe to say this is a learning opportunity for us.

We also are going to continue to tweak our flood scale. For much of the Houston metro area last week’s rains provided some on-and-off street flooding, but nothing more. Our Stage 1 and Stage 2 warnings largely reflected the urban flooding risks. But for neighborhoods along and near the San Jacinto River, these were catastrophic floods, closer to Stage 4. We need to address this discrepancy in a future version of our flood scale. The good news is that we’re working with a local university to include public feedback into this upgrade, and you’ll have a chance to participate. Look for that opportunity later this week.

In summary, this was a badly forecast rain event. I am glad it is over. It was, frankly, a nightmare to forecast. Matt and I lost a lot of sleep. We will learn from it and do better in the future.

Monday

We are transitioning to a pattern with higher pressure this week, and that will bring an end to unsettled weather for awhile. There will still be perhaps a 10 to 20 percent chance of rain today, but any showers that develop will be scattered to isolated, and fairly short lived. Otherwise expect partly to mostly cloudy skies, with highs in the mid-80s. Winds will blow from the southeast at about 10 mph, with gusts up to 20 mph. Lows tonight will be muggy, with temperatures dropping only into the mid-70s.

Tuesday, Wednesday, and Thursday

These likely will be the warmest days of 2024 so far. Expect highs to reach about 90 degrees each day in Houston, with slightly warmer conditions to the west of the city and slightly cooler daytime highs near the coast. Skies will be partly sunny with a decent southerly breeze. Nights will be warm, in the 70s. It’s been awhile since we’ve experienced this kind of heat and humidity, so please give your body some time to acclimate.

Later on Thursday, or perhaps Thursday night, we could see the return of some rain chances as a front pushes into the Houston metro area. The timing of this is still a bit fuzzy, so it’s not clear whether we’ll see any cooling on Thursday. I tend to doubt it.

Friday

Highs on Friday should be cooler, in the mid-80s, with the influx of drier air. I think we’ll see partly to mostly sunny skies, with lows dropping into the 60s. This weather won’t be chilly by any means, but it does offer a nice reprieve from the heat and humidity earlier in the week.

Saturday and Sunday

Saturday should see the driest air of the week, with dewpoints perhaps dropping into the 50s. I think we’ll see high temperatures in the low 80s for both days this weekend, with partly sunny skies. In terms of lows, we’re probably looking at the 60s, but I don’t feel super confident yet in overnight temperatures. Unfortunately for Mother’s Day, as a secondary front approaches, I think we’ll see an increase chance of rain showers—probably not anything too serious but enough to put a damper on things. If you have outdoor plans for next Sunday, please keep an eye on the forecast.

Next week

We may continue to see temperatures in the 80s for much of next week, with lows in the 60s to start the week before we return to the 70s. After some rain chances on Sunday and Monday, we should settle back down to partly sunny skies. In any case, two fronts in the middle of May are more than welcome in my book.

In brief: Morning rain has thus far been manageable, but repeated rounds of thunderstorms along and on either side of I-10 will likely cause ponding and street flooding in spots this morning and afternoon. Flood Watches remain in effect through evening.

Happening now

One round of heavy rain and storms has exited to our east. Rain totals from that round were manageable in the Houston area and most points north to Conroe. A couple flash flood warnings were needed north of Lake Livingston and back into Huntsville, where totals approached two inches. Now, we’re seeing a west-east line of storms from northern & central Harris County back past Columbus.

Rest of today

This line of storms will likely “train” west to east through the morning and early afternoon. This means repeated rounds of storms basically within 20 miles of either side of I-10. For now, there are enough gaps in between downpours to keep things mostly just annoying and not troublesome. If that continues like that the rest of today, we’ll be fine; yes there will be roadway ponding or localized street flooding but probably nothing much worse.

Eric and I have been wary about things this week because, frankly, most model guidance has struggled. But in general, things seem to be doing what was expected. So, thunderstorms this morning on both sides of I-10. Look for these to continue into early afternoon. Some scattered activity may pop up north of Harris County this afternoon, and we’ll watch for localized downpours up that way. The NWS Flood Watch continues through evening, and our Stage 2 flood alert will continue with that as well. If, for some reason this band of storms shifts farther to the north, it will not take a lot to begin flash flooding. And if for some reason, the rains over Houston remain heavy with fewer breaks, we could see more widespread street flooding. So that’s why we’ll maintain that Stage 2.

Editor’s Note: The National Weather Service Weather Prediction Center issued a discussion while I was editing this post, suggesting that heavier rain over the Houston area was likely through afternoon and could lead to more widespread street flooding. We’ll continue to watch this through the day.

Totals, as you can see from above should be generally 1 to 2 inches, with isolated higher amounts possible. Lower amounts toward the coast and perhaps to the north. Obviously, it’s been pretty rough this week in terms of forecasts and impacts, so continue to monitor the situation, and we’ll post later if anything seriously changes.

Conditions should improve this evening.

Monday and beyond

We finally begin to unwind this disrespectful weather pattern. Temperatures will begin to heat up, and we still expect low to mid-90s into midweek. Rain chances won’t be zero, but they’ll be much lower than they’ve been in recent days.

Even though the rain will quiet down, river flooding will continue this week. One river we have not discussed much is the Brazos. Things have been fine there, but the river is likely to continue rising all week and may even approach moderate flood levels by late in the week.

Beyond Friday, it’s a bit uncertain still, but assuming the river hits 68 feet or so, we’ll begin to see the flood plain get inundated, requiring the relocation of cattle. We’ll monitor this in the coming days; thankfully there’s time to prepare.

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: A few showers are possible today, but for the most part Saturday should be an okay day. Another round of storms and potential heavy rain arrives tonight and Sunday which could renew street flooding in spots. Quieter, hotter weather arrives next week.

For the latest flood gauge information, visit the National Weather Service or Harris County Flood Control websites.

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The East Fork of the San Jacinto has crested at New Caney but will only slowly fall.

To the south, the West Fork of the San Jacinto at Humble is expected to crest on Sunday and remain in major flood until at least Monday or Tuesday.

The San Jacinto will continue in major flood downstream as well, with very fast flow passing barges near I-10 which could lead to some loss of mooring.

Unfortunately, the Trinity in Liberty County is going to remain just shy of record levels for several days, allowing major flooding to continue.

Please continue to heed the advice of local officials and never drive around barricades.

Saturday morning & afternoon

The good news this morning is that radar is vacant around Houston for the first time in some time. There are a few storms passing through the Beaumont-Port Arthur area up toward Jasper, but they’re moving offshore or into Louisiana. I would expect the morning to be fine in most areas.

With daytime heating, scattered showers and a few thunderstorms should begin to develop this afternoon. These will be hit and miss; some people will see downpours, others will be dry. I expect these will move along at a decent pace. The belief is that both the movement and the actual rain rates with these will be a bit lower than we’ve seen in recent days. The best chance for this will be north of I-10 after 12 to 2 PM, which isn’t great news for areas dealing with river flooding, but hopefully they don’t add much to problems. We should make the low to mid-80s today.

Tonight & Sunday morning

Here’s why Flood Watches remain in effect. Storms this afternoon in Central and West Texas will slide east with a disturbance and likely congeal into a well organized area of rain and thunderstorms. This should arrive in our area tonight, after 12 to 2 AM or so. There are still questions regarding how this plays out. Some model guidance shows less organization to the storms and more scattered type activity. Other data suggests it will push through at a good clip. And yet other data has sort of a repetitive scenario, where we see multiple rounds of storms, much like occurred on Friday and Thursday.

For now, a widespread half-inch seems reasonable for Houston and points south, with 1 to 2 inches north of Houston. There will almost certainly be higher amounts, with the most likely areas being north of Houston. In those spots, 2 to 5 inches of rain could fall on top of already saturated ground, leading to rapid street flooding. This would be mostly a concern in the northern part of Harris, Montgomery, and Liberty Counties and points north. If you have outdoor Sunday plans, it would be best to have an indoor backup plan available.

In addition to rain, some storms could be strong with a couple perhaps producing some modest hail or strong winds.

Monday & next week

We expect the pattern to begin to transition beginning Monday into the forecast heat for next week. While a few showers or storms are possible, significant weather is not expected on Monday. The main story will be heat next week, building through the week.

Heat will build up to “major” levels, as classified by the National Weather Service, with low to mid-90s likely for highs by Wednesday and/or Thursday. Given that this will be our first real heat of the season, give your body some extra time to adjust. We’re not used to it just yet. We’ll have more tomorrow, or later today if necessary on the rain.