Matt Lanza

Good evening. Today started out as a spotty day, before thunderstorms really revved up over the northern and western halves of the metro area, including some hail in The Woodlands and eventually a tornado warning for northwest Harris, Waller, and parts of southern Montgomery Counties. As I write this, those storms have reorganized and are making one final push south and east across the area. Carpenter’s Bayou at I-10 near Channelview has received over 1.5 inches of rain in the last 15 minutes. Scattered heavy rains will slowly slide south and east and dissipate over the next few hours.

Rain totals today have been widely, widely variable.

The map above is intentionally skewed to show the north side of the metro area, as there’s been far less rain to the south today. Rain totals on the east side will increase markedly in spots before the night’s up, as this map is only through 7:45 or so. You can view more rain totals and more time scales at Harris County’s outstanding rainfall page. Rain totals were paltry to non-existent southeast of Houston and toward most of Fort Bend County.

Overnight

Looking at radar across Texas this evening, it’s pretty evident that we are not done tonight.

Storms are pooling west of I-35 this evening, which is something that had been well telegraphed on weather models the last couple days. Those will move through the area overnight.

So expect conditions to improve between now and midnight, though rain may continue at times. Weather models have been suggesting the next round of storms would arrive in Houston around 3 AM or so. I would not be shocked if that occurs a little sooner based on radar. When that happens, we’ll probably have some loud, wake your dogs up thunder, heavy rain, and potentially some strong gusty winds. The good news is that storms should be moving, so although some brief street flooding may occur, things should not last too terribly long. New rainfall should range from a half-inch to perhaps 2 inches over most of the area.

Memorial Day

Storms will exit after the morning, and we’ll probably be left with clouds and a few showers. The atmosphere will likely need time to recover, so the majority of Monday morning and early afternoon we think will be fine right now. In the late afternoon and evening, we may see conditions become more conducive for storms to redevelop. Exactly where and when? TBD. But those would probably be similar in nature to what we see occurring this evening: Slow movers, occasionally strong, and capable of putting down 2 inches in an hour, meaning a few unlucky spots may receive another few inches of rainfall with those. So yes, street flooding will again be possible under any storms.

Temperatures will be held down in the low- to maybe mid-80s.

Beyond Monday afternoon

With a low pressure system in the upper atmosphere placed just to our north and west for Monday night, Tuesday, and Wednesday, you can expect additional rounds of thunderstorms across the area, with varying degrees of intensity each time. We will likely need to watch for areas of flooding risk over more of the area through that period, details TBD. By Thursday, that upper low should begin to migrate toward Louisiana. That should mean improving weather heading into next weekend, but I don’t want to get your hopes too high just yet. We’ll keep you posted.

An active weather pattern over Texas will slowly increase our shower chances each day this weekend. Generally, the deeper into the holiday weekend you go, the better the rain chances will become. Today and tomorrow probably won’t be too bad. Sunday could see heavier rain west of Houston and Monday could see more widespread coverage of thunderstorms in the Houston area. Specifics beyond “showers and storms are possible” will be hard to come by more than 12 to 18 hours in advance; such is the nature of weather patterns like this. Let’s walk through each day and tell you what we know at this time.

Today

Expect some clouds and some sun today, with sun probably becoming more dominant as we roll toward afternoon. There’s a little more moisture available today, so we will at least mention that a shower or storm is possible. As I am finishing writing this, it’s evident that some showers have popped up out toward Wharton County and up through Columbus, well west of Houston but somewhat sudden and unexpected this morning. We think most activity should be spotty (call it like 10 to 20 percent or so), and storms should be very much the exception, not the rule today but hopefully these morning showers are not a harbinger of a busted forecast to come. We will see!

It’ll be hot and humid with highs around 90° or so for the fifth day in a row.

Tonight

Another round of showers and storms in North Texas may just have enough “oomph” to hold together as it drops south and east late tonight. We could see a shower or a thunderstorm, mainly north of Houston after 3 AM or so. For most of us? Just mostly cloudy with a slight shower chance or some mist. Lows will be in the 70s.

Saturday

On Saturday, the best ingredients for thunderstorms remain mostly inland or to our west, which means Hill Country may be the favored area for more numerous showers. We’ll call it a spotty day once again for Houston with a few showers or storms possible, once more being the exception rather than the rule. Odds of storms may go up a bit as you go to the north and west of Houston.

Look for another hot day with highs likely staying in the upper-80s or low-90s under partly to mostly cloudy skies.

Sunday

So on Sunday, the best ingredients for storms drift a little closer to Houston. While we think the coverage of storms will still be highest to the west of Houston, there should be slightly better odds for much of the area to see storms. I would say storm chances jump up close to 50 percent on average for Sunday afternoon, higher west of I-45, lower east of I-45.

Sunday’s storms could also be better organized than what we see Saturday in Texas, so heavier rain is possible. We would say that areas west of Grand Parkway up through Conroe stand the best chance of heavier rains impinging on plans Sunday afternoon. But again, specific details are tough to pin down, so most of the area has at least a chance at some storms Sunday.

A muggy Sunday morning in the 70s will give way to highs only in the mid-80s, maybe  upper-80s with clouds.

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Storms this afternoon were expected to dump heavy rain in a few small areas around the region. What we are seeing is something more robust than that, as widespread heavy rain and some areas of street flooding are ongoing. Flood Advisories are posted for the entire Houston area, and the Pasadena area is now under a Flash Flood Warning through 5:15 PM.

Radar as of 3:15 PM shows a cluster of heavy rain that has migrated west over most of the Houston area.

This is basically going to need to rain itself out now over the next 3 to 4 hours. Pasadena has been fairly hard hit with nearly 4 inches of rain so far.

 

For the sake of simplicity I’ve just shown part of the metro area above. You can always check rain totals over various times over the larger area at the fantastic Harris County Flood Control gage site. Some folks will see little to no rain (especially northeast of IAH Airport and perhaps well south toward Lake Jackson and Freeport). Others may tally 5 to 6 inches or more when all is said and done this afternoon.

So heavy rain, storms, and street flooding are likely in many spots through 7 PM. Storms will fade after that. We enter a quiet period later this evening and into the early overnight.

Round 2 of storms will arrive here later in the overnight. The timing of the next wave of storms has sped up since this morning, and it now appears we will see heavy rain and storms resume after 2-3 AM (about 2 to 3 hours faster than expected this morning). Below is what one model thinks radar will look like at 3 AM Saturday.

Other models vary a bit on timing and orientation, but all show the entirety of the region seeing a period of heavy rainfall. Another 1 to 3 inches of rain will be possible with this. This would likely lead to widespread street flooding, especially around the hardest hit areas so far with today’s rains, where the ground will be very saturated.

As for Saturday afternoon? There is a chance we see another round of rain and storms, but we still do not have much confidence in details yet to determine whether we need to be concerned or not. We will update you either tonight or early Saturday morning. A reminder that we went with a Stage 1 on our Flood Scale this morning. See our earlier post for more details on that. Stay safe, and remember to never drive through flooded roadways.

On Thursday, we expected a handful of thunderstorms to develop across the area, though it seemed likely most of us would be dry. That’s ultimately what seems to have happened in Southeast Texas, with one very glaring exception.

The area east of Beaumont, specifically between Vidor and Orange in Orange County was deluged on Thursday with up to 10″ of rain falling near Bridge City. While weather modeling did indicate thunderstorms were possible, none of the models that we saw remotely suggested this amount of rain would fall.

This brings up a key point I like to remind folks of this time of year in Texas: No matter how many models we look at, or how clear we try to be when it comes to forecasting rainfall totals, the reality in Texas is that under the right (wrong?) meteorological conditions, 4, 6, 8, 10 inches of rain can fall on any given location. We are in a very humid air mass, with yesterday’s precipitable water values running 150 to 200% of normal in parts of the region. In English, there was a lot of moisture available to dump heavy rain. Weather models won’t always tell the whole story. If a couple slow moving storms get going, they can easily dump 1 to 3 inches an hour on a location for several hours in this pattern. That’s what unfortunately happened in Orange County yesterday.

We don’t expect that to occur again today, but there will likely be some heavy storms around in a few spots. A Flash Flood Watch has been issued by the National Weather Service for all of the Houston metro area and coast from tonight through Saturday. We are growing somewhat more concerned about Saturday’s potential for widespread street flooding across the area, something that would be akin to a Stage 1 flood event for the area on our Space City Weather flood scale, which we describe in detail here.

Remember, our scale is primarily to set your expectations at a high level for the type of flooding we could see. It’s not a guarantee of what will happen specific to your backyard. We may adjust this later today or tonight as new data warrants.

Summary

The forecast over the next 24 to 36 hours is very complex. Here’s a quick summary of what we’ll go through in detail below:

Today: Most locations see a few passing showers or no rain at all. However, a handful of smaller locations in the Houston metro area have the potential to see slow moving downpours capable of producing 2 to 4 inches or more and flash flooding.

Tonight: Rain ends, then rain chances increase rapidly again after 4 AM, with heavy showers and thunderstorms likely everywhere by sunrise.

Saturday: Heavy morning storms likely with torrential downpours. Street flooding possible, if not likely. Storms should gradually end in the afternoon with a mostly quiet night.

We expect total rainfall to average 1 to 4 inches across the region. There will be many places that come in closer to 1 to 2 inches, but we also expect a couple locations to see perhaps 6 inches or more when all is said and done.

Today

Things are quiet this morning, with just a few isolated downpours in the Beaumont-Port Arthur area again.

For the Houston area, let’s call it about a 50 percent chance of showers and storms today. The problem today is the same as above in that if any storms develop and drift slowly, we could be talking about some very heavy rain for isolated spots. And some of the higher resolution models we use suggest this is a possibility around Houston. So while many of us will only hear some thunder and see little to no rain, a handful of smaller locations could see 2 to 4 inches of rain or more this afternoon. I don’t want to try and specify where those bigger ticket totals will be exactly, but based on this morning’s model guidance, they would occur somewhere in western Harris, Fort Bend, or Brazoria Counties.The Weather Prediction Center has us in a “Slight Risk” of excessive rainfall today.

 

This just underscores that flash flooding is a possibility today.

High temperatures will likely peak in the mid- to upper-80s this afternoon.

Tonight

We expect any lingering showers or storms to end around or just after sunset. Through the first part of the night, things should be quiet. Meanwhile, severe storms in West and Central Texas will likely congeal into an organized complex of thunderstorms and heavy rainfall and work east out of Hill Country overnight. We could begin to see showers develop out in front of that in the last few hours of the night. The general rule is that as we go from this evening to midnight, rain chances dwindle to near zero. From midnight through 6 AM Saturday, rain chances begin to escalate again, rapidly after about 4 AM. Lows will be in the 70s.

Saturday

As noted above, the broad summary is that a complex of heavy rain and storms will plow through the entire Houston area on Saturday morning. Some of the storms could be severe, with strong winds being the main concern. But the main concern on Saturday will be street flooding.

We should all receive anywhere from 1 to 4 inches of rain with that, though some higher amounts will be possible. Street flooding seems to be a reasonable possibility. Where things would get dicey is if the complex of storms slows down and allows for new storm development or “training” (storms moving over the same areas) on the backside, something we can’t entirely rule out. If that happens, those areas would see another 1 to 3 inches or more of rainfall and more widespread, significant street flooding would become a possibility.

Given how poorly models have performed with specifics historically in these events and how much moisture will be available, I don’t want to try and tell you that we know exactly who will see how much rainfall. We don’t. I expect that we will have a better handle on this later today, and we may post an update this afternoon or evening to clue you into what has changed since this morning.

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