To set expectations for next week’s heavy rains, we plan on implementing a Stage 2 flood alert on our flood scale, and anticipate this warning will be in effect from Sunday evening through Wednesday. This is what we mean by Stage 2 on our five-point flood scale:

Events falling into this category may cause significant, widespread street flooding across large swaths of the area, flooding numerous cars. Other examples of what we would consider stage 2 events are ones that flood dozens of homes in small, targeted areas or specific neighborhoods. These events are either moderate impact over a large area or high impact over a relatively small area.

A couple of notes on this before we jump into the forecast. First of all, it is quite early to be calling for this, as heavy rain is unlikely to arrive before Sunday night at the earliest. However, since most people probably will check out over the weekend—much of which will be sunny and pleasant—we wanted to give our readers a heads up now. Second, since we are issuing this flood alert early, it is very much subject to change. And finally, the area of greatest risk lies south and east of Houston, so that’s where we think Stage-2 like effects are most likely.

As to the overall forecast, not a whole lot has changed. There remain a number of meteorological variables that we can’t yet predict with great precision, and so the forecast models are struggling with rainfall totals. For example, a model might forecast 15 inches of rain for a location in one run, and drop to 5 inches the next run.

There is fairly good consistency, however, on the overall setup favoring heavy rainfall somewhere in Texas or Louisiana. (Or both!) So if you live within 50 miles of the coast, between Corpus Christi and Lake Charles, you’re potentially under the gun. In terms of accumulations, we anticipate 2 to 6 inches for most locations, but what we’re concerned about is potential bullseyes of 10+ inches. It looks like the most likely period for heavy rainfall will run from Monday through Wednesday.

The bottom line is this: Enjoy your weekend, but also be prepared for the possibility of heavy and potentially disruptive rainfall early next week.

We’ll update on Saturday and Sunday with the latest.

For some folks, today is the coolest morning in months! Crockett, for instance, is down into the 50s. IAH, at least as of 6 A.M. has not gotten under 70 just yet.

We will see if we can match our cool day of the week (69° on Wednesday) or even sneak just below it before the sun gets up. Either way, it’s comfortable out there today, and we’ll be closing the week on a very high note. Enjoy it, because things will begin to change in earnest later this weekend. We detail the situation below. Look for a post later today that will set our initial Flood Scale expectations for next week.

Today

No issues whatsoever. It’s beautiful. Enjoy it if you can. We will see highs peak in the 90s with abundant sunshine and rather comfortable humidity.

Saturday

While Saturday morning won’t start off quite as cool as we are this morning, it should still be a pleasant start to the day, with morning lows ranging from the 60s inland to 70s near the coast. There is even a chance that Galveston checks in cooler tomorrow than it did today. Look for more sunshine, highs in the 90s, and perhaps just a tinge higher humidity.

Sunday

The end of the weekend will bring the beginning of our transition into the wet period we’re expecting. I would expect at least a chance of thunderstorms in Houston and south of I-10 with increasing clouds elsewhere. Morning lows in the 70s will warm into the upper-80s or low-90s depending on how much sun you see. No serious problems are currently anticipated Sunday, but if you have outdoor plans, keep the rain chances in mind.

Next week

So let’s talk about next week. There are a number of factors that will go into exactly how next week plays out, some of which are rather low confidence still today. But in general, expect increasing rain chances Sunday through Wednesday, with locally heavy rainfall and potential for at least some flash flooding concerns, especially south and east of Houston and along the coast. Let’s walk through some of the players and how they will influence what happens next week.

First, the primary reason next week looks wet: High pressure over us today will leave us to the east over the weekend, steering Gulf moisture back into the area. The remains of our cold front offshore transition to what we call a surface trough. And then you may add a tropical system to the mix in northern Mexico or far south Texas. You can see this all reflected on a forecast surface map below.

Confidence is relatively high that the high pressure area will move to our east and open the door to Gulf moisture. So that much we know. Where confidence drops is in relation to possible tropical development off the Mexico or Texas coast.

Odds have been increasing that whatever moves into the Bay of Campeche this weekend will develop into a tropical depression or weak tropical storm. That’s one thing we have moderate to high confidence in: That this system has a rather low ceiling in terms of intensity. It should track along the coast and north, probably making landfall in northern Mexico or far south Texas on Monday sometime.

This will matter some, however because the exact location of the track and how well organized this disturbance is will help dictate where the highest rain chances are located and how high the totals will be. These situations are not straightforward. Sometimes you’ll see the heaviest rain hug the coast or just inland and cause flash flooding problems. Other times the heaviest rain will fall offshore and end up mostly harmless for coastal communities. We just don’t know at this point exactly what it will look like.

Here’s what I think we can say right now, with some level of confidence:

• We will have periods of thunderstorms beginning later Sunday and continuing into Tuesday or Wednesday of next week.
• It won’t rain the entire time, and there may be some substantial breaks in the rain, especially north of I-10.
• Rain will likely be heavy at times however, especially along the coast and possibly south or east of Houston.
• Localized street or flash flooding is possible, especially south and east of Houston, but it is too soon to tell you exactly where and when that may occur.
• Rain totals of 2 to 6 inches on average for most of the area between Sunday and Wednesday, with the highest totals in smaller pockets south and east of Houston, perhaps up to 8 to 10 inches or even more.
• While tropical development is becoming increasingly likely, we do not expect this to be a wind or surge issue for us. Some rough seas, rip currents, and elevated tides will be possible, but development should remain weak enough and far enough to our south to avoid the wind & surge problem. This will be almost exclusively a heavy rain situation for us.

Here is the current NWS rainfall outlook into next week.

While some areas will probably see less rain than forecast above, their placement of the bullseye totals south and east of Houston is logical right now, and higher amounts are possible in those areas.

Drier air and lower rain chances should begin to build in after Wednesday.

After we digest the morning weather model data, look for a post from Eric later this afternoon that will initiate our Flood Scale outlook for this event. And we’ll keep you posted over the weekend.

Good morning. Houston should remain in a drier pattern through the first half of the weekend—Friday evening through Saturday morning looks especially pleasant—before much wetter weather arrives by Sunday. As tropical moisture increases, so will rain chances, and we’re tracking the potential for heavy rainfall from Sunday night through the early part of next week.

Thursday

The next weak front is located north of the metro area, but should slide into the region today. There will be a subtle shift in winds from the northwest to the northeast, but skies should remain sunny regardless. Accordingly highs will be toasty today, likely reaching the mid-90s, with the possibility of a few locations seeing the upper 90s. Lows tonight will drop into the low 70s in Houston, with the potential for upper 60s further inland.

Friday and Saturday

This looks like a pretty stunning period, at least as September goes, through about Saturday evening. The driest air should push into the region on Friday, with the potential for dewpoints to drop into the 50s. Expect daytime highs around 90 degrees, with sunny skies, and lows Friday night in the upper 60s across much of Houston.

Saturday night through Monday

The period turns sharply wetter with the arrival of tropical moisture beginning Saturday night or Sunday morning. The overall threat is still not particularly well defined, but a tropical wave should move into the southern Gulf of Mexico this weekend, and associated moisture will push into the Texas coast. The forecast models are hinting at some significant rainfall totals from this, especially for locations closer to the Gulf of Mexico. For now, as a guess, we’re probably looking at rain totals of 3 to 5 inches south of Interstate 10, with lesser amounts inland through early next week. Our main concern is the potential for higher localized rain totals. It’s impossible to say where that will happen, but the potential is there.

After Monday

A fairly wet period should persist into the middle of the week, with sunnier weather potentially returning by Thursday or so. Until that time highs will only be around 90 degrees, with muggy nights in the upper 70s. Those deliciously low dewpoints will be long gone.

Tropics

It’s September 9, so as usual there is a lot of activity in the tropics. But for the western Gulf of Mexico we need only concern ourselves with the aforementioned tropical wave. This feature, which we’ve mentioned several times this week, is now given a 30 percent chance to develop into a tropical depression or storm by the National Hurricane Center. The most likely outcome is that the system will move into the Mexico coast, or possibly south Texas, but we can’t entirely be sure of that yet. In terms of the overall rainfall threat early next week, it probably won’t matter too much.

Good morning. Most of Houston is experiencing temperatures in the upper 60s to lower 70s this morning, with modestly lower dewpoints. This is not exactly fall-like weather, but it’s a reminder that we’re much closer to fall than you might realize. Moreover, there’s another weak front on tap in a day or so to keep our “September-pleasant” weather in place for the rest of the week.

Wednesday

Today will be hot, as drier air allows the air to warm quickly into the low- to- mid 90s under sunny skies. Light northerly winds will shift to come from the east later today, and eventually the southeast. This will herald the return of somewhat muggier conditions later tonight as the first weak front washes out. As a result low temperatures Wednesday night may be a few degrees warmer than Tuesday night.

Thursday and Friday

Another weak front will be on the move Thursday, however, and it should reach the coast by around noon or shortly thereafter. This one should have even a little bit more drier air with it. So while highs on Thursday will warm into the mid-90s beneath sunny skies, lows Thursday night should drop to around 70 in the city, with cooler temperatures in outlying areas. It will be nice. Expect similar conditions for Friday, which should see the driest air of the week.

Saturday

The drier air should hold into Saturday before our air mass becomes modified by the onshore flow. Still, I’m expecting mostly sunny skies for the first half of the weekend, with highs in the low- to mid-90s. Saturday night should be warmer and muggier.

Sunday and beyond

The party ends on Sunday as notably higher dewpoints in the mid- to upper-70s return to the region. Along with this we’ll see an abrupt shift in cloud cover and increasing rain chances. We still don’t have a great handle on rainfall amounts, but daily chances should be about 50 percent beginning on Sunday, continuing through much of next week. Highs will be around 90 degrees each day, with lows in the mid-70s.

Tropics

In the tropics we’re still tracking Hurricane Larry, which will avoid Bermuda and should gradually weaken as it lifts to the north. Closer to home, in the Gulf of Mexico, Invest 91L is moving toward the Florida Panhandle, where it has a 50 percent chance of becoming a tropical depression or storm before landfall. Regardless, it will make for a wet few days in Florida. Finally, we’re continuing to see the potential for a weak tropical system to develop in the Bay of Campeche late this weekend. However there is no real signal in the forecast models that this system will either develop further or move that much northward. Still, its moisture could play a role in our rainfall next week.