In brief: The weekend has started off calmly, in terms of rainfall. Most likely we will see that start to change later this afternoon or on Saturday evening, with scattered to widespread showers and thunderstorms.

Setting expectations for the rest of the weekend

So far, today, moderate to heavy rainfall has remained offshore in proximity to low pressure over the northern Gulf. This has given us a quiet start to Saturday. The question is, does that mean the threat of rainfall is over for the Houston region?

I do not think it is. We are seeing daytime heating over much of the area, and this should help provide a spark for some shower development over land later this afternoon and evening. Predicting exactly where remains a challenge, but some of our guidance is pointing again to areas just north and west of central Houston, which were hard hit by showers on Thursday night.

Broadly speaking I expect fairly widespread showers to develop over our region from mid-afternoon onwards, perhaps lasting through most of the evening. For the immediate coast, the threat may persist a little longer. For most of us, this is likely to bring 0.5 inch of rain, or less, so more of a nuisance than anything consequential. But we could definitely see some bullseyes with 2 to 4 inches in isolated areas, leading to street flooding.

Showers remain possible on Sunday, but should be more scattered in nature. Drier air starts filtering in on Monday, leading to somewhat lower humidity and basically ending our rain chances for the time being.

In brief: Houston’s radar has quieted down after Thursday night’s widespread showers west and north of Houston, but our rain chances will continue through the weekend. Also, next week looks sunny, with notably lower humidity.

Thursday night surprise

It’s safe to say we did not expect to spend Thursday evening watching a mass of showers continue to creep into the Houston region from the west. Rather than more or less halting in the Brazos Valley as expected, the storms kept coming, bringing 3 to 6 inches of rain to a broad area from south of Katy all the way north into The Woodlands. Some locations in western Montgomery County, near Magnolia, picked up more than 8 inches. It was a wild and wooly night in these areas, but most creeks and bayous have thankfully remained within their bayous. The radar over this region has quieted down overnight, but because the high-resolution models behaved so badly with this system, it diminishes my confidence in the forecast for storms over the remainder of the weekend. Nevertheless, we press on.

Friday

We are seeing a few scattered showers near Galveston Bay this morning, but nothing too serious. In terms of activity today, I think pretty much the entire region faces the possibility of showers and thunderstorms through about 7 to 9 pm today. It is difficult to pin down a specific part of our region at risk, but I don’t think we’ll see the organized mass of storms we saw Thursday night. Rain chances will likely diminish overnight. Highs today, with mostly cloud skies, will range from the upper 80s to about 90 degrees.

Saturday and Sunday

Over the weekend the focus of rainfall will shift closer to the coast, where a low pressure system will bring moisture and other ingredients necessary for heavy rainfall. Everyone will have the potential for showers and thunderstorms this weekend, but the greatest risk will be for coastal areas, and locations generally east of Houston. For these locations rain chances will be in the vicinity of 70 percent each day. Areas hard hit by rains on Thursday night will likely see lesser coverage. In terms of timing, rains appear most likely from Saturday afternoon into Sunday. Highs will be in the mid- to upper-80s. Lows will be in the 70s.

Next week

Monday should be partly sunny, with lower rain chances, and highs in the 80s. Some time later on Monday a modest cool front will push some drier air into the region. Don’t set your expectations too high, as this won’t exactly be crisp fall weather. But after a long and humid summer, even a little bit of fall will feel just fine. Look for highs in the mid- to upper 80s for most of next week, with sunny skies. Lows will be in the upper 60s to lower 70s. As for humidity, with dewpoints in the 60s the air will feel more comfortable, but not exactly dry.

We will update the site later today, or this weekend, if needed to cover the threat of showers and street flooding this weekend.

In brief: Storms have moved further east than anticipated this evening, and we are instituting a Stage 1 flood alert for locations along and to the west of Highway 59/I-69 for Thursday night. We’ll reevaluate the situation early Friday morning.

A mass of thunderstorms associated with a slow-moving front has edged further to the east than expected this evening, bringing heavy rains to some locations north and west of the central Houston region. Most totals have been manageable, in the 1 to 2 inch range. But some locations near Cypress and Waller have picked up 4 inches, and parts of western Montgomery County have seen 4 to 6 inches.

As of 8:15 pm these storms have progressed to a line from roughly Katy north to The Woodlands. Our latest high resolution modeling indicates the mass of storms could move a little bit further east, perhaps as far as Highway 59, before petering out this evening by around midnight. For areas currently receiving rainfall another 1 to 2 inches is possible in some locations tonight, with street flooding the principal threat, which is why we’ve put the Stage 1 flood alert into place.

We then expect a quieter period early on Friday and into the morning hours. After that? We will have to see about that in the morning.

In brief: In today’s post we provide an overview of Houston’s rain chances over the next four days, which will be elevated. Although there’s the potential for some heavy rain, we’re not too concerned about flooding at this time. A modest cool front arrives early next week.

Wet pattern overview

An upper-level low, in concert with the remains of Hurricane Polo, is bringing heavy rains to the Texas Hill Country this morning, and these storms are moving toward the I-35 corridor. This system will progress eastward across Texas, but it should stall later today to the west of Houston, near the Brazos Valley. Several inches of rain are possible from this system in Central Texas, but the Houston region should not see major effects aside from the potential for scattered showers and thunderstorms today.

For us, the best rain chances will come from Friday evening through Sunday morning as a weak frontal boundary slowly trudges through the area and stalls near the coast. With ample moisture this setup will bring the potential for heavy rainfall into the region during this time period, especially along the slow-moving boundary. Whether this rain falls just inland, or off the coast, will depend on precisely where the boundary stalls. All in all, through Sunday, most of the Houston region should pick up 1 to 4 inches of rain. We are not planning to issue a flood stage warning on our flood scale at this time, but we will continue to monitor things closely.

Quick space note

Weather permitting, four astronauts will launch to the International Space Station this morning aboard a Crew Dragon spacecraft from Florida. The crew includes NASA astronauts Jessica Watkins and Luke Delaney, Canadian astronaut Josh Kutryk, and Russian cosmonaut Sergey Teteryatnikov. Launch is set for 10:10am for this Crew-13 mission. We wanted to send a special shoutout to Kutryk, a fan of Space City Weather! Safe travels to all.

Thursday

The last day of September was another hot one, with high temperatures in the mid-90s for inland areas of Houston. Phew! Highs should peak in the lower 90s today across the city, and then after today or Friday, we should be able to say sayonara to the 90s for awhile. As noted above, the heavy rainfall due to Polo’s remnants should stay west of Harris and surrounding counties. However we will see scattered to widespread showers today, and the heaviest cells may quickly produce 1 or 2 inches of rain in isolated areas. Most locations will see considerably less, however. We’ll see some gusty southerly winds again later today. Overnight lows will drop into the upper 70s, and rain chances will slacken, but not go away entirely.

Friday, Saturday, and Sunday

It will be a soggy weekend, yes. But at the same time it’s not going to rain everywhere, all the time. There will definitely be breaks in the showers, so if you’re planning to attend a festival, or a college football game, or something else, do not abandon all hope. Nevertheless our region will see its best rain chances in weeks, and there will be more clouds than sunshine. Rain totals will vary widely, but most areas should get 1 to 4 inches. What concerns me most is the potential for these showers, tropical in nature, to produce briefly heavy rainfall. But again, aside from possibly the immediate coast, we don’t expect too much of that behavior over the Houston region. If our expectations change, of course, we’ll update here. Temperatures will gradually push downward, with highs in the upper 80s on Friday dropping to the mid-80s on Sunday, and overnight lows going from the upper 70s to lower 70s.

Next week

A slightly stronger cool front is really in the cards for early next week, likely arriving Monday night. This should lead us to sunny days in the 80s for most of next week, with nights in the 60s or lower 70s. Humidity will be lower, but as this is still one of our early fronts don’t expect miracles on that score. Still, it won’t be Houston-like houmidity, and after our long summer it’s going to feel fairly pleasant out there. Just don’t expect sweater weather just yet.

Tropics

You may start to see some noise about tropical development in the Southern Gulf or Bay of Campeche next week, and some of our models are showing the potential for modest development there. We don’t have any real concerns about this in Texas, however, as any systems that develop there next week will most likely move to the northeast, away from the state.