Eric Berger

In brief: In today’s post we discuss the increasing potential for a tropical storm form in the Gulf this week, and what that will mean for Houston’s weather as the system stays away from the Texas coast.

Will Isaias form?

The big news this week is that we actually have some tropical action in the Gulf, and even though it is early October seas there are plenty warm for intensification to occur. However, as Matt as discussed over on The Eyewall, there are a number of factors to consider. But the bottom line is that, more likely than not, Tropical Storm Isaias will form during the next couple of days. There is a chance, perhaps about 1-in-3, that it eventually becomes a hurricane.

To be clear, the storm is not coming to Texas. The system should eventually move to the northeast (slowly) before coming ashore on Friday or Saturday somewhere between Louisiana and the Florida Panhandle. It is likely to be a prolific rainmaker for some (still to be specified) areas along the northern Gulf coast. As for what happens in Texas, and more specifically the greater Houston region, we are likely to see tides elevated by a foot or two later this week. And since we are going to be on the backside of the system, it should amplify a northerly flow into Houston on Friday and Saturday.

Tuesday and Wednesday

These will be mostly sunny and warm days, with moderate humidity. We can expect highs in the upper 80s to lower 90s, with moderate northeasterly winds. With dewpoints in the mid- to upper-60s or thereabouts, it is going to feel moderately humid, but not oppressively so. Nighttime lows will be in the lower 70s. Rain chances are very low, perhaps 10 percent.

Thursday, Friday, and Saturday

Skies will again be partly to mostly sunny during this period, but we should see a slightly drier flow due to the Gulf system. Highs will still be in the vicinity of 90 degrees, but nights should drop into the upper 60s to 70 degree range in Houston, with even cooler conditions possible further inland. Humidity should also be a touch lower, especially on Friday and maybe Saturday. Daily rain chances remain on the order of 10 to 20 percent daily.

Sunday and the early part of next week

By Sunday, or so, a more southerly flow should return, and this probably will bring a few more clouds into the forecast. Highs are likely to remain somewhere in the upper 80s to 90 degrees, with fairly warm nights in the mid-70s. Rain chances should increase by Monday or Tuesday of next week, but the details are still pretty fuzzy.

A real front?

We have yet to receive a real fall cold front that knocks nighttime temperatures down into the lower 60s, or even 50s, and really whacks humidity down. I’m not guaranteeing that will happen next week, but it does seem possible toward the next of next week, in the Thursday to Saturday time frame. We’ll keep an eye on things, because at some point it would be nice to step outside and say, “Ahhhhh.”

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.