Matt Lanza

Back to our regularly scheduled gross late summer weather

Yesterday was nice. It wasn’t perfect, no, but it’s a start on our road to autumn. Unfortunately, like many Houston freeways, the road there is still under construction. More on that in a second. First, some news.

NOAA has completed their analysis of rainfall return period in Texas. Those maps we’ve utilized for 100 and 500 year floods are now officially obsolete. In the Houston area, a 24 hour rainfall of around 13″ used to be required to classify a rainfall event as a “100-year flood.” Remember a “100-year flood” is a flood that has a one-percent chance of occurring in any given year. That 13″ rainfall has been revised up to 18″ of rain in 24 hours to qualify as a 100-year flood. Basically, what we used to define as a 100-year flood is now a 25-year flood. I think most of us knew this already; it had been telegraphed last year, but we can now make it official.

Why is this changing? The previous maps are decades old. The primary reason is that we have more data and better data to work off of. We also know, based on plenty of data, that rain events are getting bigger in Texas, and this is especially disproportionately true in the Houston-area. Ultimately, there will be ramifications because of these map changes. Infrastructure is built to these map standards. Floodplain regulations are based on these map standards. These changes have been well-telegraphed since Harvey, so some of this process is already underway. But it’s a slow process, so don’t expect changes next month. It’s a start, however.

On to the weather…

Today

Radar is mostly quiet this morning, though we are beginning to see a few showers near the coast as of 5:30 AM. More noticeably, we still see a good deal of cloud cover in the area.

A satellite loop shows low clouds (white), mid-level clouds (yellow), and high clouds (dark colors) moving through the area this morning. Sunshine will be at a premium, especially southeast of Houston today. (College of DuPage)

On the loop above, the bright white indicates lower stratus clouds and the darker colors indicate higher cirrus clouds. The yellow offshore indicates showers and mid-level clouds. Bottom line: We have a lot of clouds around, so sunshine will be limited today, especially south and east of Houston.

As the day goes on, we expect to see scattered showers and storms develop, initially near the coast and spreading a bit further inland as yesterday’s cold front begins to return as a warm front. Look for high temperatures today to hit the low-to mid-80s.

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Dreary, unsettled weather returns to Houston

After a few days off, unsettled weather returned on Thursday, bringing some folks over three inches of rain. Others saw nothing at all, but everyone is likely in line to see at least some rain over the next couple days.

Today

Radar isn’t too active this morning with a few scattered showers — mostly light or occasionally moderate rain.

Radar shows a smattering of showers or lighter rains across the area this morning. (College of DuPage)

As we go into the rest of today, look for scattered downpours and thunderstorms to blossom from later this morning into this afternoon. Like yesterday, we could see locally heavy rainfall in the most persistent storms. Rain amounts will again vary wildly, with some folks seeing little to no rain, while others could see two to four inches in a relatively short time, along with some localized street flooding.

Saturday & Sunday

Unfortunately, the specifics surrounding the forecast this weekend are going to be difficult to lay out. If you’ve lived in Southeast Texas for any length of time, you know that our rain often follows a pattern of feast or famine: Neighborhoods that get soaked may be adjacent to dry neighborhoods. Trying to predict where and when it’s going to rain this weekend is impossible to do more than a few hours in advance, but we know that both Saturday and Sunday carry high chances that it will rain for a period of time during the morning or afternoon hours.

Specific rain amounts will vary significantly from place to place through Sunday evening. On average, expect an inch or two, with some places seeing more and others less. (NWS)

Total rainfall should add up to about an inch to two inches on average across the region by Sunday evening. Some folks will see less than that. Others may see three, four, or five inches of rain or even a little more with some street flooding. If you have outdoor plans this weekend, include an umbrella and an indoor backup if possible. Where the heaviest ultimately falls will depend on how far south a cold front can push, along with other small-scale processes in the atmosphere.

If there’s good news in all this, it’s that our six day string of 90°+ weather should end. We’ll see high temperatures in the mid-80s, with lows in the mid-70s. Yes, it will be unpleasantly humid, but at least it won’t be obscenely hot for later September.

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Tuesday evening update on Houston rain & tropics

Good afternoon and evening. I wanted to offer a quick update on Houston’s rain situation, as well as Invest 95L.

Tonight through Thursday

The Flash Flood Watch that had been in effect for the region has been cancelled. We did see some significant rains southeast of Houston this morning.

We do expect more rain and thunderstorms to develop tonight, but the heaviest should primarily remain offshore. That said, watch for locally heavy downpours in spots and at times, especially southeast of Houston along the coast tonight and tomorrow. Some short-fused street flooding can’t be entirely ruled out. But we don’t expect widespread issues tonight or Wednesday. With storms offshore tomorrow morning, inland showers and storms will probably be a little sluggish out of the gate, but do expect at least a few downpours tomorrow around the region. Eric can narrow this down with a little more specificity in the morning.

We’ll see more scattered storms on Thursday, and we’ll pin that down for you a little better tomorrow.

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Rain, rain (won’t quite) go away

After an on-again/off-again dry summer in the Houston area, the last 10 days have felt like we’ve been dodging a continuous faucet. We will continue to deal with this into later this week and weekend.

Quick situational awareness for you:

  • A Flash Flood Watch is in effect generally along and southeast of US-59, so primarily for the coastal counties in our area until later today. A watch means flooding, especially street flooding, is possible.
  • We’re expecting periods of rain, possibly heavy at times, through tomorrow, with a bit more possible Wednesday and Thursday.
  • Our Caribbean/Yucatan tropical disturbance (Invest 95L) remains disorganized this morning. The National Hurricane Center (NHC) gives it a 60% chance of development as it comes across the Gulf later this week. We think the ceiling on intensity is low, but this system does bring more locally heavy rain risk to parts of Texas.

Through Thursday

As I write this morning, heavy rain is south and east US-59, mainly impacting coastal Brazoria County and much of Galveston, and Chambers Counties.

This morning’s radar loop shows the heaviest rains south and east of Houston, a trend that should hopefully continue pushing offshore today. A Flash Flood Watch remains in effect south & east of the city through this afternoon. (College of DuPage)

A Flash Flood Warning is posted for the west shore of Galveston Bay through Texas City back into western Galveston County. That goes until 7 AM, as they’ve seen healthy amounts of rain in that area overnight.

Look for rain to continue this morning, though with perhaps a gradual focus more to the east or offshore. It’s possible areas north and west of Houston stay quiet much of this morning before some scattered downpours this afternoon. The most likely area to see rain continue at a healthy pace at times will be along the coastline or near Galveston Bay.

Additional rain of one to three inches is possible along the coast and just inland. If rain hugs the coast longer than expected this morning and afternoon, totals could be higher in Galveston through Freeport. Areas north and west of Houston will see more sporadic, scattered amounts of less than an inch in most cases.

An additional 1-3″ of rain will be possible through early Wednesday morning south and east of Houston, with lesser, more scattered amounts north and west. (NWS)

More rain will be possible tonight, once again along the coast, however we expect the heaviest rain tonight to stay south and east of Houston and mostly offshore. Flash Flood Watches are expected to expire as long as that remains the case We’ll re-evaluate that later today and probably have a brief update for you this evening and let you know if NWS extends the Flash Flood Watch through tonight for the coast.

From this vantage point, the forecast for Wednesday and Thursday is pretty straightforward: Scattered showers and thunderstorms are likely on both days. We still need to iron out specifics and details, but expect more pockets of locally heavy rain, though they aren’t expected to be widespread at this point. Just a generic, “It’s probably going to rain at a few points between both days” will have to suffice for now.

Clouds and rain are at least holding down temperatures. Look for temperatures to range from the upper-70s to around 80° if it stays cloudy and dreary all day to the mid-80s if we see some occasional sunshine.

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