Eric Berger

In brief: Houston faces a wet Labor Day Weekend, but our flooding concerns are clustered primarily along the coast. Mostly cloudy skies will keep a lid on temperatures over the holiday weekend, keeping things dare I say almost comfortable outside most of the time? We are also tracking the tropics as they begin to heat up.

Good morning. We’re providing updates through this weekend on Space City Weather due to the ongoing potential for heavy rainfall through early next week. However, our Stage 1 flood alert remains in effect only for coastal counties, from Galveston County eastward. This is where our modeling continues to indicate the potential for some street flooding over the next several days. For example, here’s where the likelihood of heavy rainfall is greatest for today:

The rains into next week will be driven by an upper-level low pressure system lingering off the Texas coast. As we discussed on Friday, there is a small possibility this system develops tropical characteristics with a surface center of low pressure over the Labor Day weekend, but most likely its main impact will be as a rainmaker for coastal areas.

As often happens with these systems, the heavy rainfall is clustered mostly offshore. But areas such as Galveston Island and Bolivar Peninsula will be well within the threat area, and may pick up 5 or even 10 inches of rainfall through the middle of next week. It won’t rain all of the time, but coastal counties should expect a pretty decent soaking through about next Wednesday.

As for areas further inland, including most of the Houston metro area, showers will be hit or miss this weekend. Rain chances will depend on how far you live from the coast, but over the Labor Day weekend you can at least expect a healthy chance of a passing shower or thunderstorm each day. One benefit of the cloudy skies this weekend is cooler temperatures, particularly for the end of August and into early September. Highs, for the most part, will be in the upper 80s to about 90 degrees each day—and even cooler closer to the coast. Often, we’re 10 degrees hotter at this time of year.

Tropics

We’re starting to see activity pick up in the tropics. If you want a full rundown, please check The Eyewall later this morning, where Matt will have a comprehensive update on everything we know before noon today. In addition to the aforementioned system in the northwestern Gulf of Mexico, we’re also closely monitoring a tropical wave in the Central Atlantic. It will move into the Caribbean Sea early next week.

There it will find blazing hot seas, but at this time most of our modeling guidance is not too aggressive about developing it into a tropical storm or hurricane early next week. However, toward the end of next week this wave/tropical system will be nearing the western edge of the Caribbean Sea. After that point it could move into the Gulf of Mexico. We’re talking about a period 7 to 10 days from now, so uncertainty is very high. There’s not a whole lot we can say about what happens at that point, so we’ll continue to watch it.

Have a great Labor Day Weekend, everyone. We’ll be back with another post on Sunday morning to assess things.

In brief: On Friday afternoon the National Hurricane Center began tracking an area of low pressure over the northwestern Gulf of Mexico. To put this threat into perspective, we’re going to share content published earlier today on The Eyewall. Though a serious system is not likely to develop, locally heavy rain and flash flooding are a good bet along the coasts of Texas and Louisiana into next week

We’ve been discussing it all week on The Eyewall, but low pressure has now officially formed in the Gulf, with a surface low analyzed offshore of Galveston and Sabine Pass. The National Hurricane Center now highlights this area with a 20 percent chance of development.

The surface low is rather broad, so it’s not as if we have a rapidly intensifying tropical system off the coast. But we have low pressure in the Gulf, which is always something of note. Any development risk from this is very low-end in terms of winds and waves. But in terms of rain, this will be a source for some serious coastal rainfall in the coming days, development or no development. Rain totals through next week may tally up an additional 5 to 10 inches between Galveston and Vermilion Bay in Louisiana.

While there are no flood watches posted currently (except in the New Orleans and Baton Rouge areas), there is some potential for flooding to occur in coastal counties and parishes. Places like Galveston, Port Arthur, and Cameron through Morgan City and New Orleans could definitely see at least localized street flooding crop up. With a surface low now offshore, most of the rain will likely consolidate around that feature, meaning that inland places like Houston and perhaps Lake Charles see less rain, less often.

This will be a very coastal-focused feature. The low should meander in the days ahead offshore. Thankfully, upper level conditions aren’t super conducive for development, so again any organization or strengthening would probably be very sluggish and the ceiling from this is rather low it seems. As the system meanders, it could end up onshore in Louisiana or back toward the middle Texas coast, so proximity to land will also act against its development.

Bottom line: This is not a major concern, but it bears some watching and it will, at the least, deliver locally heavy rain and flash flooding potential on the Texas and Louisiana coasts.

In brief: Today is the first of several days, likely lasting through the Labor Day weekend, that the Houston area will be subject to the potential for widespread showers and thunderstorms. For most of our region these will be a nuisance, but for the immediate coast there is the potential for street flooding, which is why we’re initiating a Stage 1 flood alert for coastal counties.

Stage 1 flood alert

We are putting this flood alert, based upon our flood scale, in place due to the potential for heavy rains near the coast during the next several days. A Stage 1 alert simply highlights the potential for intermittent street flooding, particularly in low-lying areas, and possibly along some feeder roads. I anticipate keeping this alert active through Labor Day Weekend.

It applies to coastal counties across our region: Matagorda, Brazoria, Galveston, Chambers, Jefferson, and Orange. Essentially, that’s the entire upper Texas coast. The reason is that these areas will be closest to the source of moisture, and susceptible to the most frequent rainfall. Some of our latest modeling indicates the heaviest rains will be further east, in the Beaumont-Port Arthur area, but I feel the entire upper Texas coast is at risk. These coastal areas could see 5 to 10 inches of rain over the next week, with higher isolated totals.

Thursday and Friday

After rainfall of a more scattered nature for the last couple of days, showers and thunderstorms should become more widespread beginning today. As noted above, rain chances will greatest right along the coast, but all locations along and south of Interstate 10 will be prone to periods of medium- to heavy rainfall, with lesser chances further inland. Rains today and Friday will be driven by a combination of lots of moisture in the atmosphere along with an upper-level low pressure system that will help drive the formation of storms.

Based upon high-resolution modeling, which is not great but the best we have, I anticipate showers and thunderstorms to start developing over coastal areas around 8 to 10 am this morning and then persist, on and off, for much of the daytime. Activity may diminish somewhat this evening before redeveloping on Friday. With plenty of cloud cover, high temperatures today should remain in the upper 80s for most locations, although some inland areas with scattered sunshine may reach the lower 90s.

Labor Day Weekend

Widespread showers and thunderstorms, particularly for coastal areas, will likely persist from Saturday through Monday as the atmosphere remains ripe for showers. Houston, particularly inland areas, will not see wall-to-wall rain this weekend, but there definitely will be the potential for storms to pop up and mar outdoor activities. Intermittent showers and clouds should help keep highs to the upper 80s to about 90 degrees for most locations this weekend, so this will definitely be one of the cooler Labor Day Weekends we have had of late.

Next week

Rain chances will persist on Tuesday and Wednesday before slackening some toward the second half of next week. This probably will allow high temperatures to claw their way back into the lower 90s. I don’t want to jinx anything, but there is a non-zero chance of a weak cool front pushing through in the September 8 to 10 period. Right now I would give it about a 25 percent chance, based on the medium-range modeling. Even if it doesn’t happen, the mere fact that we’re looking at the possibility of fronts suggests that fall may not be all that far off.

Tropics

As August comes to an end, the lull we’ve been enjoying for awhile now is likely to come to an end as well. There is increasing model support for the development of a tropical system in the Central Atlantic which will then move toward the Caribbean Sea. After that? There’s not agreement in the models, so pretty much anything could happen. But given that we’ll be in early September at that point, it’s definitely worth keeping an eye on the tropics.

In brief: Today will again see scattered rainfall across the metro area before more widespread showers and storms push into our region beginning tomorrow. The period of Thursday through next Tuesday should see daily rain chances above 50 percent, so make any Labor Day plans in Houston and Galveston with a backup indoor option.

Wednesday

Today is probably the final day with only “scattered” showers and thunderstorms rather than more widespread storms. Locations south of Interstate 10 probably have about a 50 percent chance of rain today, with lesser chances inland. Skies will, accordingly, be partly sunny and high temperatures for most regions are likely to reach the lower 90s. This probably will be our hottest day for the next week. Low temperatures will drop into the upper 70s on Wednesday night.

Thursday and Friday

Rain chances will be higher to end the work week, likely in the vicinity of 70 or 80 percent for most locations. I expect these to be mostly passing showers, so accumulations during each storm will likely be one-half inch of rain, or less. With partly to mostly cloudy skies, most locations should see high temperatures in the upper 80s to around 90 degrees.

Labor Day weekend

Unfortunately, if you were hoping to end summer with a beach bash over Labor Day weekend, you’re likely to be disappointed. The combination of plenty of moisture from the Gulf of Mexico and a couple of upper-level low pressure systems will keep the threat of daily rainfall high, especially for locations closer to the coast. Daily rain chances over the holiday weekend will be in the 60 to 80 percent range. These showers won’t last all day, to be sure, but they’re likely to put a damper on outdoor activities. Highs will range from the upper 80s to about 90 degrees for most locations.

Next week

Conditions on Monday and Tuesday of next week may become even more favorable for showers, and the potential for heavy rainfall. We’re not ready to call for a Stage 1 flood alert for coastal areas, as I want to see more data. But the potential is there. Regardless, the threat of moderate to heavy rainfall will persist for the entire region, along with highs in the upper 80s to 90 degrees.

By Wednesday or so, the potential for widespread showers starts to diminish, and the latter half of next weekend probably will start to see more sunshine and less rainfall. Highs probably will get back into the low-90s.

Tropics

The National Hurricane Center is continuing to track a couple of areas that have a low-end chance of developing, but in terms of the Gulf of Mexico there is not a whole lot that gives me pause about the next week or so.