Good morning. We’re entering day two of a period that has the potential to bring significant rainfall and flooding across the metro area. The pattern is threatening because it may produce both short-term, intense rainfall as well as prolonged, widespread showers. Most of us should be fine in the end, but this kind of setup is worth monitoring very closely.

We are going to implement a Stage 2 alert on our Flood Scale for two reasons. While we do not think most of the area will see significant flooding, we do believe there is definitely the potential for localized flash flooding, especially on Wednesday and Wednesday night. Second, soils across the area are already wet, with reservoirs at full capacity.

Monday

Our overall confidence in the forecast today is low. While there is the potential for heavy rainfall, there is also some drier air in the atmosphere, and this may limit activity over the Houston region to scattered showers and thunderstorms. In any case, the best chance for heavy rainfall will lie just east of Houston, along Interstate 10 and heading into Louisiana. For the Houston area, most of us can probably expect accumulations of 0.25 to 1 inch of rain. Skies will otherwise be mostly cloudy, with highs in the low- to mid-80s. Rain chances back off tonight.

Tuesday

The disturbance in the upper atmosphere that is driving all of this unsettled weather will move closer to our region, and therefore the chance of heavy rainfall will increase somewhat on Tuesday, especially north of Interstate 10. (This could be a serious day for flooding in the Dallas-Fort Worth area). However, this does not mean the day will necessarily be a washout in Houston. I expect rainfall accumulations for most to average 0.5 to 1.5 inches, with the potential for more of course. Highs again will be in the 80s.

Wednesday

We still think Wednesday and Wednesday night will be the period that brings the best chance of heavy rainfall and flooding to the Houston metro area. This is when the upper-level low pressure system will pass more directly overhead. Basically, there should be enough moisture and lift to produce some very heavy rainfall. But whether the epicenter of this occurs along the coast somewhere from Matagorda Bay to Galveston, more inland over Houston, or north of The Woodlands, we just cannot say right now. I think most of the area will see 3 to 6 inches of rain from Tuesday night through Thursday morning, with the potential for some pockets of 10 inches or more. Where that occurs we just don’t yet know. This uncertainty is reflected in the large red area in the excessive rainfall forecast below.

Thursday and Friday

We think the potential for really heavy rain will start to dial back on Thursday morning as the upper-level low exits, but there should still be a healthy chance of showers and thunderstorms on Thursday and Friday. Both of these days should see mostly cloudy skies, with highs in the low 80s.

Saturday and Sunday

Some sunshine should return by the weekend, but I think we’ll still see at least some scattered to widely scattered showers on Saturday and Sunday. Highs will be in the low to mid-80s. Skies should turn mostly sunny by early next week.

Matt will have an update by around 7 pm CT on Monday.

For the vast majority of the Houston area, today was pretty uneventful. Across Harris County, according to the Flood Control map, the max total was 1.64 inches along Buffalo Bayou at the Beltway. But as you went southwest along Highway 59, things escalated quite a bit. The max total in our region today was 13.47 inches (as of 3 PM) in Wharton County, just east of Ganado.

That wasn’t a typo. And a simple look at that map shows the problem and trouble with forecasting these types of events. You go from 13 inches just east of Ganado to about 5 inches in the town itself. Raise your hand if you expected 13 inches of rain in our regional neighborhood today. I sure didn’t. Neither did any weather model. But with these sorts of setups, this is exactly what can happen, and that’s one thing that makes forecasting in Southeast Texas so difficult sometimes. This is also why we’re being a little coy on details regarding this event. Because quite simply, they’re extremely difficult to predict, let alone try and communicate.

So the headline right off the bat here is that we are going to continue to tell you to expect us to activate our Space City Weather Flood Scale tomorrow. We remain unsure if it will start at Stage 1 or Stage 2, but Eric will update you in the morning on that. Likewise, the National Weather Service is holding off on Flood Watches for tomorrow given the uncertainty on how things evolve tonight. Which leads me to…

Tonight

What happens tonight? Well, the radar this evening still has a good bit of rain south of Houston. But the real ridiculous 2 to 4 inch per hour stuff seems to mostly be gone or pushing offshore.

There are some blobs of heavier showers east of Houston. And truth be told, that is the area I want us to watch closest tonight. One model in particular has been indicating that storms are going blow up after 3 or 4 AM along some lingering boundaries from today’s storms. And that would occur closer to Port Arthur or between Baytown and the Beaumont/Port Arthur area. So I would think that if we see heavy rain blow up again overnight, that would be the region to watch.

Tomorrow

Monday’s forecast will entirely dependent on what happens late tonight, so I’m just going to leave it at: There’s a good chance of scattered showers and thunderstorms tomorrow. Heavy rain is definitely possible. But the details are still very sketchy, and modeling disagrees on exactly who is at highest risk across Texas tomorrow. That said, we should see a little less chaotic weather tomorrow across the state than we have seen today (though the Panhandle will be at risk for some big storms).

Beyond tomorrow

Eric did a great job this morning summing up what I’d call the “known unknowns” of the forecast over the next several days. And to be honest, after digesting the models, not much has changed. That’s not terribly surprising. As I alluded to above, these types of patterns are notorious for being full of capricious details, and I fully expect certain modeled outcomes today to become outdated before too long.

The National Weather Service outlook for total rain the rest of the week is above. I would view this as an “average” outcome. On average, your backyard could see as little as 3 or 4 inches of additional rain, but more likely closer to 6 or 8 inches. And some places could see much more than that. Suffice to say, this forecast is challenging, and we’ll keep you posted throughout as things evolve. You’ll want to stay plugged into the forecast. Our next update will be our usual Monday morning update from Eric.

Good morning. We’re already starting to see the development of rain showers to our west and southwest, and this marks the beginning of what will be a very wet week for much of the eastern half of Texas. This activity will be driven by a slow-moving upper-level low pressure system and an increasingly moist atmosphere. There is a lot we still don’t know, but here’s an overview of what to expect.

Today

Storms will move from the southwest into the metro area later this morning, but we think their rainfall intensity will weaken a bit as they spread into Houston. Our general expectation is for 0.25 to 1 inch of rain for much of the Houston area, with higher totals to the southwest. The greater risk is over Brazoria, Wharton, and Jackson counties.

I-45 threat

Much of the model guidance suggests that the biggest threat for heavy rainfall this week will come along the Interstate-45 corridor from Houston through Dallas, with 6 to 10 inches of rainfall coming between now and next Friday, with the potential for higher isolated totals somewhere. If you’re traveling to or from the Dallas Fort Worth area, take that into account.

Activity may spike Wednesday

The potential for heavy rainfall will exist every day this week given the overall atmospheric conditions, however we think the most active period will come on Wednesday or Wednesday night as the upper-level low pressure system moves directly overhead. This is when the potential for heavy rainfall should spike over the Greater Houston area, and we could see some flooding. However, given that we’re still more than three days from this time frame, we just don’t have that much confidence in the details for Wednesday and Wednesday night’s rainfall. We plan to implement a Flood Scale alert tomorrow, as we get better data.

Rain chances continue through Saturday

Although the heaviest rainfall should end some time on Thursday, the threat of at least moderate rains should continue into Saturday before high pressure asserts itself.

Will there be flooding?

This is the big question. For most of the region, six inches of rain spread out over six days is really no problem. However, it becomes a problem if six inches come in a few hours, in which case we’ll see street flooding, and bayous begin to back up.

We’re starting from a point of reasonably dry soils, but if your area gets 1 inch today, another inch spread over Monday and Tuesday, and then 8 inches on Wednesday then there could definitely be problems. We just don’t know where this rainfall spike will occur. We’re fairly confident that some location between Matagorda Bay to Houston to Lake Livingston will see a bullseye of heavy rainfall on Wednesday or Wednesday night, and this will cause at least localized flooding. But where? We just don’t know yet.

Matt will have an update this evening, by 7 pm CT.

Well, we sure hope you got to enjoy the weather yesterday and hopefully today too. Mid-May fronts with cool, comfortable air masses feel like a rare treat. Our morning low of 62° at Bush Airport this morning is the coolest morning this late in the season since May 25, 2017 (60°). The humidity returns later today, tonight, and Saturday, and then rain chances will follow. Our area looks poised to enter into a prolonged unsettled weather pattern for at least least a week or so. Let’s walk through the forecast.

Today

Really, we will just have a nice day ahead today. Look for some sun after these morning clouds in spots dissipate. There will still be a fair number of clouds though this afternoon, and highs will be around 80° or in the low-80s, give or take.

Saturday

Saturday morning will start a bit warmer and a bit more humid than today or Thursday began. Morning lows will be in the 60s, if not 70° or so in most places. Look for a mix of clouds and maybe a bit of sun. If you have the option to choose between weekend days for outdoor plans, we would strongly suggest going with Saturday. While there will be a chance for some showers, mainly west or southwest of Houston, those chances are not especially high or long lasting. It will be warm and turn increasingly humid, with highs in the 80s.

Sunday into Monday

The forecast for Sunday is very challenging. This is mainly due to timing. The last couple days have seen the start time of rain slip in models from Saturday night to Sunday morning to now Sunday afternoon. What we know is that a disturbance is going to cross through our region, and it will likely bring most of us a period or two of showers and thunderstorms on Sunday through Monday.

We may have one area of rain Sunday morning and afternoon move into the area from the west. Rain may then taper off late on Sunday afternoon before another round fires up either Sunday night or Monday morning into afternoon. The exact timing is tricky, but we know most folks will see at least a little rain. You can see from the animation below how precipitable water or how much moisture is available in the atmosphere increases sharply through Sunday morning and afternoon, which will turn a slight rain chance into a fairly healthy one.

Look for highs near 80° or in the low to mid-80s depending on exactly when it rains. Lows will be in the upper-60s to low-70s.

How much rain to expect Sunday and Monday? Always a difficult question to answer, but right now we could see a half-inch to inch on average with some localized places perhaps seeing as much as 2 to 3 inches of rain or even a bit more. Where those bullseyes occur is difficult to predict more than 12-18 hours out, so I won’t speculate on that this morning.

Rest of next week

The rest of next week will feature Texas under the influence of a pattern with lots of moisture around and several disturbances and a dreaded upper low passing across the state. That is a classic spring combination for periods of rain and thunderstorms. Why do I say “dreaded?” Because upper lows are notorious fickle and difficult to forecast. As the saying in meteorology goes “upper low, forecaster’s woe.”

Here’s what we know: The chance of rain will be high each day next week. But, it will not rain all day or perhaps even every day everywhere. More likely we’ll have a day with widespread, heavy thunderstorms separated by a day or two of more isolated or scattered activity. As of today, it appears that Sunday into Monday and later Tuesday into Wednesday have the highest odds of more widespread storms. But I’ve dealt with enough upper lows to tell you that this could easily move around, hence why we’re just blanketing each day next week with a rain chance. We’d expect rain chances to tail off a bit by next weekend.

So how much rain should we expect next week? Well, it’s probably going to vary, widely. Some areas may see an inch or two, while other areas could easily see 4 to 6 inches of rain or even some more by Friday. On average, we would say about 1 to 3 inches should be expected. We don’t think those bigger ticket rainfall amounts will be especially widespread, and we don’t expect major flooding issues right now. But this is the type of forecast we’ll want to watch closely. If necessary, Eric and I will break out the flood scale, but it’s much too soon for that.

Meanwhile, we’ll do our best to try and isolate those heavier periods of rainfall that make travel difficult for you, and if we gain some confidence in those or rain amounts, we’ll also update this weekend.