Matt Lanza

Eric and I just want to provide a quick update on the situation that is expected to evolve tonight southwest of the Houston metro area. There have been a few things that have come together today to lead us to think a significant thump of rain is possible in the Matagorda Bay area, extending into Wharton and possibly southern Fort Bend and Brazoria Counties at times. For the vast majority of the Houston metro area, periods of rain are expected, some of which could be heavy, especially in the southern half of the metro area. But serious, widespread flooding is not a concern for us at this time.

How much rain is expected?

As of right now, the thinking is that a general 4 to 8 inches of rain will fall between this evening and tomorrow morning for those areas in Matagorda, Wharton, and Jackson Counties.

There are a couple models we utilize for higher resolution in these types of events that are spitting out some pretty hefty totals, in excess of 10 to 15 inches. So in a worst case scenario, we could be talking about some pretty big rain totals down there. Some of the heavier rains could extend into southern Fort Bend, Brazoria, or Colorado Counties. Galveston County could be on the fringe of heavier rain at times also.

Why is this a problem?

Besides the obvious reason that 8 to 10 inches or more is a lot of rain, the area just southwest of the Houston metro is especially vulnerable right now to flash flooding. Gauge data from the Lower Colorado River Authority (LCRA) shows that once you get close to Bay City, 72 hour rainfall totals have been up over 4 to 7 inches.

Basically, an area that has seen this much rain already cannot handle 8 to 10 inches or more of it, so flash flooding is very likely to begin quickly as heavy rain falls.

Could the rain forecast change?

Absolutely. Models are pretty locked in on the region of greatest impact tonight (southwest of Houston), but their performance has struggled at times this week. We are dealing with a slow moving non-tropical system that is behaving like a tropical system. There’s inherent uncertainty on the finer details of the forecast, but for the most part we know that heavy rain is likely in spots, primarily southwest of Houston, and that heavy rain should be enough to cause flash flooding down that way.

Is there a chance this shifts to the Houston area?

As noted above, forecasts can change of course. But right now we feel pretty confident that the risk of serious flooding will not expand into the Houston metro area. Modeling is in good agreement on this, the meteorological variables are best aligned for heavy rain to the southwest, and those areas have had much more rain than the Houston metro has over the last 3 days. That doesn’t mean there won’t be periods of heavy rain in spots tonight. That also doesn’t mean that we won’t have any street flooding issues to contend with. Those are possible, as they always are when heavy downpours are forecast. But we do not expect serious, widespread flooding in Houston.

Why no flood scale alert?

This is a little trickier to answer, but basically since we don’t expect more than some nuisance street flooding in the Houston metro area right now, we are holding back the flood scale. At best it would be a Stage 1 for Houston. But for Matagorda, this would be higher than that, so we don’t want to confuse people southwest of Houston, needlessly panic the bulk of our readers in the Houston metro area, or send any kind of mixed message in general.

The bottom line is: Heavy rain is possible anywhere tonight. Street flooding is always a possibility, though we don’t believe it will be a huge deal in Houston. Significant, potentially widespread flooding is possible in Wharton, Jackson, and Matagorda Counties.

How does Friday look?

Without getting into too much detail: Expect scattered showers and thunderstorms, but the overall coverage of the rain should begin to decrease again tomorrow, as previously expected. We will have the latest for you on that in the morning.

Well, I was hopeful that maybe we could identify a period over the next several days that didn’t look unsettled. While it isn’t going to rain everywhere the entire weekend, the chance of rain is going to be higher than usual everywhere from tonight through Tuesday or Wednesday of next week. We will walk you through things as best we can today, and we’ll conclude our Friday post with an update on Tropical Storm Elsa.

How much rain through next week?

We’ll start off today’s post by addressing the question most people probably have: How much rain are we expecting, and will it flood? Rainfall totals are going to vary widely from location to location, but we’re confident that most places should 2 to 4 inches through Wednesday. That said, given significant amounts of atmospheric moisture (high precipitable water, or PWATs), any storms will be capable of producing 1 to 3 inch per hour rainfall rates. So it’s pretty obvious that some locations will see a good bit more than 4 inches over the coming days. Where exactly those locations are is to be determined.

But as you can see from the map above, the current bullseye is just east of Houston. For those curious, the European model has its bullseye over the Sabine River, and the GFS does not really have a bullseye. But most models are in good agreement with this forecast above. You can expect a good bit of rain in the coming days.

Will it flood? This question is somewhat thornier. At this point we don’t expect significant flooding, but the reality is that we can’t rule out things getting a little dicey in spots at times. Even though there will likely be street flooding in spots at times, we are not yet going to trigger the Space City Weather Flood Scale. I do think at some point between now and Wednesday we are going to have to give in with a Stage 1 or 2 type event possible. Things can change, so stay with us through the holiday weekend, and make sure you have downloaded our app!

Today

Friday is going to start off fine. Look for sunshine and a few clouds. Today will probably be pretty hot, with highs in the mid-90s likely. I wouldn’t expect much worse than a couple hit or miss showers through 3 PM at this point. After 3 PM, a cold front begins to sag south into northern parts of the area, and we should see more organized storms break out along or north of Highway 105, dropping into Hempstead, Magnolia, The Woodlands, and Liberty this evening.

Tonight & Saturday

Those storms will continue pressing south after dark, reaching I-10 around or just before midnight, although they could weaken some. A few additional scattered storms will be possible overnight.

On Saturday, we get a surge of moisture (near-record PWATs for the date) that should allow for numerous showers and storms to break out across the region. I would expect a bit of atmospheric “bumper cars” to ensue tomorrow as boundaries collide, popping off new storms across the area in a chain reaction of sorts.

Showers could push or focus south of Houston tomorrow late day or evening.

Temperatures will be held down with clouds and rain. Look for lows in the 70s and highs in the mid-80s.

Sunday

Expect numerous showers and thunderstorms throughout Independence Day, with locally heavy rain possible. Highs will be in the 80s.

What to do about fireworks displays? Well, I wouldn’t be cancelling anything just yet. We are certainly talking up a wet weekend here, and the cancellation option is a very plausible one in some places. That said, there is a good chance that some parts of the area will be just fine for fireworks displays, albeit with some soggy ground to watch from. That decision should be as close to a game time one as possible.

Monday & Tuesday

It’s a bit of a tough call as to which day from Saturday through Wednesday has the best chance for the heaviest rain, but if I were a betting man, I might lay a few chips on Monday or Tuesday. We get a boost in moisture on those days, especially Tuesday and some pretty vigorous upper level support for rain too. Not everyone will see their heaviest rain early next week, but I think some people will, and this is where I would begin to perhaps be more mindful of flash flooding risks.

High temperatures will be held down here. Look for mid-80s at best (probably low-80s or even cooler in spots) for highs and 70s for lows.

Wednesday & Thursday

For the middle of next week, we currently expect to see things begin to wind down a bit. Expect scattered thunderstorms on Wednesday, but we are hopeful that the coverage will be noticeably less than it was on Monday and Tuesday. By Thursday, much will depend on what Tropical Storm Elsa does, but assuming it stays well east of us as forecast, we would probably just see sun, clouds, some isolated to scattered storms (unrelated to Elsa) and slightly warmer temperatures. We’ll see. But it appears that the pattern may begin to change back to a more typical summer one by late next week.

Tropical Storm Elsa

(Editor’s Note: Elsa was upgraded to a hurricane immediately after publication) Elsa did some work overnight getting better organized as it approaches Barbados and the southern Leeward Islands today. Max winds are now 60 mph, and although the National Hurricane Center forecast currently falls just short of Elsa becoming the season’s first hurricane, there is some chance it could attain that intensity.

The forecast right now is officially comfortably east of our area, with a focus on Florida by Wednesday or Thursday of next week. There is still a very wide spread of options available to Elsa beyond day 3 or so, meaning that folks from Central Louisiana through the Bahamas, including all of Florida should still be monitoring Elsa’s progress closely. We continue to think this won’t be a direct issue for Texas, but we will monitor its progress and any track forecast changes through the weekend anyway.

Welcome to another edition of our weekly tropical outlook. The last two hurricane seasons have been full of many quick developing, lower-end storms. Some folks deride the National Hurricane Center for “wasting time” naming these things, but if it looks like a duck and quacks like a duck, whether bloated, thin, short, tall, round, square, or what, it’s still a duck. And that’s why we have added another storm since last week.

If you blinked, you might have missed Tropical Storm Danny yesterday, but it formed off the coast of South Carolina, made landfall and weakened to a depression within about 12 to 18 hours. It wasn’t quite like Imelda, and its fast forward motion will keep it from becoming a Carolina or Georgia version of Imelda, but it went quickly, and it came from an area I didn’t even mention a week ago. So go the tropics.

Tropical outlook in a sentence

While there is one area in the Atlantic for us to monitor, it will likely face an uphill battle to make it to the Gulf in a position to develop any more significantly.

Invest 95L

The area people have been watching a good bit since last week is Invest 95L, which today does not pose much risk of making it to the Gulf. It will likely either stay disorganized and continue across the Caribbean (where it will face mountains of shear) or it will develop a little and get pulled north toward the Bahamas, Florida, or Eastern Gulf. Colloquially, some of us in meteorology will use the phrase “weaker, wester” to describe these things. It seems highly unlikely that 95L makes it to Houston. The National Hurricane Center has just lowered odds of development risk on 95L to 30 percent over the next 5 days.

Invest 97L

The one area I want to focus on is the new Invest 97L, which now has a 40 percent chance of developing over the next 5 days according to the National Hurricane Center (up from 20 percent this morning).

As you can see on satellite above, Invest 97L has some loose thunderstorm activity, but it is not yet organized. The one thing about Tropical Storm Danny: Say what you will about it being “pathetic” or whatever, but at least it had that swirly cinnamon bun look going for it yesterday. 97L is not there yet.

Invest 97L will be steered west or west-northwest around the periphery of high pressure in the Atlantic. Both key operational models, the Euro and GFS tend to buy into Invest 97L developing over the next three days. However, they differ significantly on *how* much development occurs. I’ve plotted the GFS and European models below, showing you what we call 850 mb vorticity. What? That’s a good map to look at to gauge where things stand with potential development risk. And you can indeed see both the GFS & Euro show ample “spin” (yellow & orange) and low pressure near the entrance to the Caribbean on Friday morning, with the Euro on the left and the GFS on the right.

The difference is that the GFS is far, far more aggressive in organizing Invest 97L over the next 3 days. Why does this matter? Because the GFS has been the only model showing this coming to the Gulf as a significant storm. If it’s unrealistically strong 3 days from now, that doesn’t bode well for its accuracy on days 7 to 10. So right now, using context clues, there is a good shot we see the potential for a tropical depression or storm approaching the southern Lesser Antilles by the end of this week.

From there, this will have a mountain to overcome. The Caribbean is full of shear, and any system will not be greeted by favorable conditions on the other side of the islands. While the GFS keeps this going somewhat across the Caribbean, the Euro rips it to shreds. Neither model’s ensemble is particularly bullish on this system’s future either. So sitting here on Tuesday, I find it difficult to think that Invest 97L will make it to Texas as an organized tropical entity.

That said, the weather pattern over Texas is likely to say fairly cool and wet for most of the next 2 weeks. It gets tough to think that a tropical system makes it here as an organized system, but a bigger risk could be that the moisture gets here and exacerbates an already wet Texas.

That’s a wet Texas to say the least. So the bottom line is that we’ll want to sort of watch this system for its moisture. But at least at this point there’s no reason to think it’s going to become a problem for us, and I can’t point you to any reliable, outlier model guidance that says it will. We will let you know if that were to change.

Beyond this, expect a quieter tropics for a little while, as the atmospheric background signals (what we often call the “intraseasonal phase” of the atmosphere) is fairly suppressed over the Atlantic basin, meaning it will inhibit storm formation. That doesn’t mean we won’t see a storm or two, but in general, storm development risk should be lower than it has been. This could allow for our first significant Saharan dust event of the summer as well sometime in mid-July. We will see.

We’re starting the day just a tiny bit less humid than yesterday. It has sure felt like summer the back half of this week. The humidity will remain high, but temperatures are going to gradually step back a bit as rain chances kick back up later in the weekend.

Friday & Saturday

Both today and tomorrow should feature mostly similar weather. Expect a mix of sun and some clouds, with highs in the low to mid-90s and lows in the mid to upper-70s, along with fairly high humidity. Rain chances will be pretty typical for this time of year, with at least a few showers or thunderstorms around. There could be a slight uptick in storm chances late Saturday afternoon or evening as the pattern over our area begins to change to one dominated by a trough in the upper atmosphere. This would be especially true south and east of Houston.

Sunday & Monday

Both Sunday and Monday will probably see scattered to numerous showers and thunderstorms. Monday may have slightly more coverage than Sunday, but both days will see considerable chances of rain at virtually any point in the day. Look for highs in the 80s, especially Monday. Lows will be in the 70s.

Rest of next week

The overall weather pattern next week will be a bit odd across the country, with all-time record breaking heat in the Pacific Northwest (seriously, just an incredible and disconcerting weather event up that way, amid a historic drought too; both events carrying the fingerprints of climate change), a hot East Coast, and a cool trough sort of stuck over the Central U.S.

What does this mean for Houston and the surrounding area? Well, it means we shouldn’t see any severe heat next week. Yay, us. High temperatures will actually be held down some because of higher rain chances. Days with more rain will be in the mid to upper 80s. Days with less rain should be in the low-90s. Lows should be in the 70s.

As is often the case, pinning down the exact timing of showers and storms and who will see the most rain is a bit of a meteorological slog; we just don’t know yet how things will precisely unfold next week. But suffice it to say there will at least be chances of rain or storms each day. Right now I’m favoring Tuesday and maybe Friday for the greatest coverage of storms, as the trough tries to reload itself nearby later in the week. But we’ll fine tune that through the weekend.

How much rain should we expect? As of right now, I don’t think this will be a major, widespread excessive rain event. But, a healthy 1 to 2 inches should be expected in most places on average between now and next Friday, with the regular caveats that some places could see more and others a little less. I do think areas south and east of Houston have a higher chance of seeing some of those higher amounts.

At this time, we don’t expect to have to use the Space City Weather Flood Scale, but we’ll be watching closely the next few days to see if that thinking changes.

By the way, it’s a good time to download our weather app, so you can know right away if any changes to the forecast occur this weekend! Tap here for Apple. Tap here for Android.

Tropics

We continue to watch this tropical disturbance (Invest 95L) way out in the deep Atlantic, and also way out of bounds for what is normal this early in the season. The National Hurricane Center has dropped development odds on this one a little since yesterday, sitting at 30 percent as of 1 AM CT.

We’ll get another update not long after I publish this post.

As of right now, we don’t think this has much of a future in front of it as it treks across the Atlantic. Given how out of bounds it is climatologically and a somewhat hostile road west, development, if any, would be very slow and possibly erratic. Probably nothing we will need to ever worry about, but it’s certainly nothing for us to worry about right now.

More on Monday morning or perhaps Sunday, if necessary.