In brief: A round of storms moving into the region today should impact areas south of Houston, including southern Brazoria County which has already been hard-hit by rainfall. Storms should be more scattered in nature on Friday before the likelihood of widespread heavy rainfall ramps up over Memorial Day Weekend.

Rains recap

Since the beginning of these late May storms on Tuesday, most of the Houston area has picked up 1 to 3 inches of rainfall, which has been manageable. However areas south of Houston, particularly in southern Brazoria County near Angleton and Lake Jackson, have had a far wetter time of it. Some of these locations have already received 6 to 8 inches of rainfall. Unfortunately for these locations, it appears that rainfall on Thursday will be mostly concentrated over areas south of Interstate 10.

Thursday

A check of the radar this morning shows a large mass of showers off to the southwest of Houston near Victoria Port Lavaca. These showers and thunderstorms should slowly move to the northeast, toward the metro area this morning. Our latest high-resolution guidance suggests these storms will largely remain confined to areas south of Interstate 10 as they move through during the morning hours, and likely exit to the east by early afternoon. Rain accumulations of 1 to 3 inches will be possible for coastal areas, but I’m hopeful that much of the heavier rain will fall just offshore.

For the rest of the Houston area rain showers and thunderstorms should be more scattered later this afternoon. Skies will be mostly cloudy with high temperatures in the upper 70s to lower 80s. (I have to say that afternoon temperatures on Wednesday afternoon were very comfortable for late May in Houston). Rain chances should be low overnight, with lows around 70 degrees.

Friday

This is looking like a day during which showers and thunderstorms are more scattered in nature rather than organized into a broader system; which is to say rain chances will be a bit lower than the weekend at about 50 percent. With mostly cloudy skies we can probably expect highs in the vicinity of 80 degrees.

Memorial Day Weekend

The upper-air pattern will become more amenable to supporting widespread showers and heavy rainfall this weekend as a low pressure system allows the passage of multiple disturbances over the region. Rain chances will be near 100 percent on Saturday and Sunday, and perhaps only a little bit lower on Monday. Most of the area is likely to pick up an additional 3 to 6 inches of rain this weekend, with higher isolated totals leading to at least street flooding, and possibly some flash flooding. For this reason we are maintaining our Stage 2 flood alert through the holiday weekend.

It’s still a little too early to have precise details about timing, but basically you should be prepared for some disruptions at any point this weekend. Certainly roads should be passable most of the time, but these are the conditions that support some impacts to mobility where rainfall is heaviest and/or prolonged. Basically we want you to be alert to the possibility of flooding, but not fear widespread mayhem.

High temperatures should remain in the low- to mid-80s this weekend with plenty of humidity, and nights not cooling down much. Saturday looks to be mostly cloudy, but we could see some breaks in the sky on Sunday and Monday when it’s not raining.

Next week

I don’t have great confidence in the forecast for next week. Daily rain chances continue to look healthy, perhaps in the vicinity of 50 percent or so, but at this point I think (and hope) amounts will be trending downward after Monday. Highs remain in the 80s, probably.

In brief: Tuesday night’s rains were mostly manageable, but they are just the first round of storms that our region will experience over the next week. We now believe the heaviest rain is likely to come this weekend, when flooding concerns will be greatest.

This is just the beginning, not the end

In recent years Houston has often experienced a pattern in which we will see one or two days of rain before a front moves through, or high pressure sets in, or something else happens to turn off the spigot. Then we’ll have a few weeks of sunny skies and no rain. Only rarely have we seen periods of several days of moderate to heavy rainfall as we are now experiencing.

The ongoing rounds of storms that will rotate into Houston through Memorial Day weekend, and possibly beyond, is probably due to the early phases of an El Niño that appears to be developing in the equatorial Pacific Ocean. This generally promotes a wetter pattern across Texas. This El Niño is likely to peak later this fall or over the winter months, and based on recent model forecasts it could be a rather strong El Niño. So maybe we will see more prolonged periods of rain, and fewer prolonged periods of dry weather.

In any case, the rounds of showers and thunderstorms that passed through the Houston region overnight are likely to continue into early next week. It won’t rain all the time, but for most locations it probably will rain at some point each day. Saturday and Sunday look to have the best chance of precipitation, which will probably spoil a lot of Memorial Day weekend plans. So it goes here at Space City Weather where we don’t control the weather, we just get blamed for it. We’ll be here all weekend, alongside you.

Wednesday

The storms that rolled through over night brought between 0.5 and 3 inches of rain to most locations. As expected, all streams, creeks, and bayous are well within their banks this morning. Flooding will become more likely this weekend, as rain accumulations stack up, and for this reason we issued a Stage 2 flood alert on Tuesday, and plan to hold it in place through the holiday weekend.

Light to moderate rains are ongoing this morning, and the overall trend is one toward weakening rather than strengthening storms. Activity will shift southward over the next couple of hours, and I expect the rains to end entirely across the Houston metro area by or before noon. This afternoon we may briefly see some partly sunny skies, with high temperatures pushing into the mid-80s or so. Lows tonight will fall into the mid-70s. As for rains, I expect low-end chances through the evening hours, so if you have outdoor plans for later today I would be cautiously optimistic.

Thursday and Friday

By early Thursday, with our atmosphere recharged, we are likely to see another rain-making disturbance moving into the region from the west. I don’t know whether these storms will be as widespread or active as what we experienced Tuesday night, but they definitely will have the potential to produce another 1 to 3 inches of rainfall. Another, similar, round of storms will be possible at some point on Friday. Highs on both days will be in the low- to mid-80s, with partly to mostly cloudy skies. Again, there are likely to be extended periods when it is not raining, so there will be some time to get outside and enjoy the moderate temperatures (for May).

Memorial Day Weekend

This weekend often kicks off summer in Houston, with sunny skies and our first temperatures in the low- to mid-90s. Well, not this year. A surge of moisture should lead to widespread showers and thunderstorms on both days, with some of these showers producing very heavy rainfall.

By this point we may see rain accumulations from storms this week pushing up to 4 to 8 inches for some locations, so we’ll be tracking creeks and bayous closely. Harris County has an excellent tool for you do to this for locations near you. The National Weather Service also has a good resource for tracking river flooding in our region. Rain chances by Monday may drop to 70 percent.

Highs will be in the low 80s, probably, and if we continue to get morning storms there may be some breaks in the clouds during the afternoon hours. Basically, you’ll need to continue to remain weather aware.

Next week

After Memorial Day rain chances will probably fall back some next week, but we probably are still looking at something like at least 50 percent daily. This, as well as ongoing partly cloudy skies, should help keep temperatures in check for the remainder of the month—which is to say we might not see 90 degrees again until at least early June.

In brief: After a mostly quiet Tuesday, the potential for widespread showers and thunderstorms will increase tonight and into Wednesday morning. Here’s our latest thinking.

This post will only cover the forecast for Tuesday evening through Wednesday morning. However, in the big picture, not much has changed with our forecast through Memorial Day weekend. We still expect periods of widespread and, at-times heavy rainfall. Our Stage 2 flood scale alert remains in effect through that time.

As for tonight, we still do not have great confidence in the finer details of the forecast. But there are a lot of red flags out there, including an atmosphere that is extremely rich with moisture, an approaching (but dying) front, and a fair amount of instability. This, typically, leads to moderate to heavy rainfall. There’s still a chance this could bust, but I do feel as though the region will see some activity tonight.

As a best guess, I think we’ll see a line of storms, possibly broken, form north of Houston roughly along Highway 105 tonight around midnight, or maybe a bit before. This line of storms should then move southward shortly after midnight. Possibly we could see some damaging winds within the stronger storms, but the bigger threat is heavy rainfall. Whether those storms hold together all the way through the Houston metro area and down to the coast is not entirely clear, but that mess should be moving offshore before sunrise.

Even as it does so, another mass of showers and thunderstorms may advance into Houston from the west. Most of our guidance indicates that the threat of rainfall from these storms will be highest along and south of Interstate 10, so basically areas closer to the coast. These storms could reach Houston around sunrise on Wednesday, give or take a couple of hours, before weakening. Or maybe the atmosphere will already be too worked over for them to have too much impact.

Again, there’s a fair amount of guesswork here, but we wanted you to be aware of the potential for heavy rainfall overnight—amounts will vary broadly, from 0.5 inch to 4 inches (maybe) in isolated areas—and into Wednesday morning.

We’ll be back by 7 am with a full forecast for you.

In brief: In today’s post we’re are initiating a Stage 2 flood alert through Memorial Day Weekend due to the potential for periods of heavy rainfall that will accumulate in creeks and bayous over time. Please remain weather aware for the next week.

Overall pattern

With the complete breakdown of high pressure, plenty of moisture in the atmosphere, and an upper air pattern that will eject a series of disturbances into Texas from the southwest, the next seven days (at least) should feature periods of moderate to heavy rainfall. During this time accumulations of 4 to 8 inches of rainfall are possible, with higher amounts likely in some areas. As rainfall totals stack up over time they may bring some rivers, creeks, bayous, and other waterways to flood stage. For this reason we are putting a Stage 2 flood alert into effect through next Monday. This means that while most of our roads should be fine most of the time, there will be the potential for flash flooding, and you should remain weather aware.

You have questions, we don’t have answers

Let’s start with this fact: The large mass of showers moving into southwest Houston this morning was not well predicted. This underscores the reality that timing these atmospheric disturbances (which produce the lift and other conditions needed for rainfall) more than 24 hours out will be difficult. I know there are a lot of graduations later this week, and weekend, in addition to graduation parties. It is that time of year. Unfortunately there is no way I can sit here on Tuesday morning and tell you whether it will, for sure, rain on Friday evening, Saturday afternoon, or whenever.

All we can really say is that there is a good likelihood of rainfall, some of which may be heavy. Some of these showers may come in the form of thunderstorms, but the overall threat for severe weather beyond rainfall is not particularly high. It also will not rain all day and night, certainly, but the potential for showers during the daytime, through Memorial Day, is pretty high, especially over the weekend.

There are some benefits to all of this. Although Harris County is now drought free, many areas near Houston remain in a moderate to severe drought. Additionally, you may have heard about the water crisis in Corpus Christi. This will not end the problems there, but the potential for 3 to 6 inches of rainfall over the next week in the Coastal Bend area will provide some help with at least short-term water issues. And finally, instead of high temperatures around 90 degrees, we are going to be in the low- to mid-80s for the rest of the week.

Tuesday

Well, if you read yesterday’s forecast post, you may recall that I thought most of the daytime on Tuesday would be rain-free. Surprise! The arrival of a round of showers from the southwest this morning means that we could see intermittent showers through about noon. I think the stronger storms associated with this system will mostly remain off the coast, but we can’t rule out some moderate or heavy rainfall in the Houston region this morning. After this we probably will see some partly sunny skies this afternoon that will allow high temperatures to push into the mid- or possibly upper-80s. It will be plenty humid.

Then, beginning this evening, a weak front will approach and should move into the area from the north. I am not totally confident in how this system will progress, but we can probably expect a line of storms to develop north of Houston around sunset (i.e. in the vicinity of Conroe), and then propagate south into Houston this evening before reaching the coast around midnight, give or take. I suspect these storms will weaken as the move into the city, you should nonetheless be prepared for the possibility of thunderstorms this evening, and into early Wednesday across the region.

Wednesday

This will be a partly to mostly cloudy day, with highs probably in the mid-80s. Rain chances during the daytime hours will likely depend on how worked over the atmosphere is on Tuesday night (i.e. more widespread storms on Tuesday evening would probably lead to less coverage on Wednesday during the daytime, and a weaker line of storms on Tuesday would allow for more widespread showers and thunderstorms on Wednesday). Anyway, I’d peg rain chances in the vicinity of 50 percent. After today, rain chances will increase for the rest of the week.

Thursday, Friday, and Memorial Day Weekend

In general we expect these days to have mostly cloudy skies, highs in the lower 80s, and overnight lows in the mid-70s. That’s the easy part. In terms of rainfall, each day will have rain chances in the vicinity of 70 to 90 percent, with slightly lower chances during the overnight hours. It would be a fool’s errand to try and predict precisely when it will rain, or when the heaviest rainfall will occur. Just know that the pattern will be broadly supportive of rainfall, and that as amounts accumulate we may well see street flooding and flash flooding (rapidly rising waters). Generally mobility will probably be OK most of the time, but probably not all of the time for everywhere. We, at Space City Weather, will be with you the whole period. It’s not exactly the Memorial Day Weekend festivities we envisioned either, but here we are.

Next week

Rain chances will remain healthy next week, but probably take a step back to around 50 percent daily. Maybe. Honestly, it’s difficult to predict when this overly wet and cooler pattern will end with any confidence.