The most intense storms that developed early Friday morning have been winding down as we approach the middle of the day, and this general weakening trend should continue through the afternoon.

For most of us, the rains have been more than manageable so far, with 1 to 2 inches across much of the region. But areas north and northwest of central Houston, including northern Waller County and western Montgomery County, have received 4 to 6 inches. While bayous remain mostly within their banks, these rains have saturated soils in the region.

Given the unpredictability of this kind of weather system, we still have lots of questions about the forecast. As a best guess, the next area to watch later today will be the Matagorda Bay region, and the potential for storms that develop there to migrate into the Houston area overnight and on Saturday.

Matt did an excellent job of summarizing things in this morning’s post, but the bottom line is that we still expect a situation where some area roadways may see high water during heavy rains. However, we’re not concerned about flooding of homes and businesses at this time, and think bayous are well positioned to handle these rains. For this reason we remain solidly in a Stage 2 flood alert, and don’t anticipate the need to increase this.

There may be some let up in storms on Saturday afternoon or evening, before a final round of storms pulses through the area on Saturday night and Sunday morning. Again, we think this will be mostly manageable for the area’s floodways, but you should be aware of the potential for moderate travel disruptions through Sunday morning.

We will post our update no later than 9 pm CT on Friday evening.

The forecast situation across the Houston area is walking a fine line between very beneficial rainfall and “alright, you can stop now.” Based on model data this morning, it would seem most of the area will see the beneficial aspects, but there remain concerns that some parts of the area may get a bit more than hoped, and because of this, we are going to shift from stage 1 to stage 2 on our Space City Weather Flood Scale.

Flood watch

A flash flood watch was hoisted by the National Weather Service yesterday evening, right about the same time we posted about calling for a Stage 1 flood event on our Space City Weather Flood Scale. Our reasons for escalating to stage 2 are laid out here.

What does it all mean? You should interpret all of these things to mean that street flooding is a very good bet today and at times through Sunday. It would be a good idea to adjust your plans around the weather the next couple days.

Could it get worse than this? Thankfully, we are starting off with low water levels and dry ground. So it will take a little time for grounds to truly become saturated. Remember, flash flooding is less about how much rain falls and more about how quickly it falls. Rainfall rates are expected to be 1 to 3 inches per hour at times. Initially, that can produce street flooding, hence why the flash flood watch is in effect today. Rapid rises will likely occur within bayous today, but at this point, we would expect them to remain within their banks. After today, the ground will be more saturated, and if we were to see several hours of 1 to 3 inch per hour rain rates tomorrow or Sunday morning, then we could begin talking about something a little more serious. For now, expect street flooding to be the main issue, but we are going to watch things closely today and tomorrow in case this does escalate.

So, you’re bumping to a Stage 2 flood alert? Given that this looks to be a bit beyond just nuisance street flooding (Stage 1) and will likely have some more significant localized impacts (Stage 2), we are going to upgrade our flood alert to a Stage 2 this morning. For most folks, Stage 1 impacts of nuisance street flooding are all you will see. But given the “training” aspect of heavy rain rolling over some places again and again and the excessive rates (1-3″ per hour), we do believe a few locations may see a bit more than just nuisance street flooding, more akin to a Stage 2 event. In the interest of full transparency, the risk of this escalating to a Stage 3 type event, while not especially likely, is not zero, and this is something we will be watching closely this weekend.

So how much rain are we talking? On average, we expect most places to receive 2 to 4 inches of rain by the time we get to Sunday evening.

Some may receive a bit less. With 1 to 3 inch per hour rates, yes, others will receive a good bit more than this. Most models do indicate that the maximum total rainfall in very, very localized areas could reach 10 to 12 inches or even a little more. Given the setup today, I would expect the highest chance of those max totals to be north or west of Highway 59.

Today

Radar this morning shows heavy rain lined up mostly on the west side of the city stretching on an axis from Port Lavaca through Wharton, the Katy area, Cypress, up into The Woodlands and Conroe and northeast to Lake Livingston.

Notably, it’s around Lake Livingston where the heaviest rainfall is causing almost 3 inch per hour rates this morning. Closer to Houston, Kuykendahl at Spring Creek has seen over 1.3″ in an hour as of this writing. As I was about to press “post” here, a Flash Flood Warning was just issued for parts of Waller, Montgomery, and Walker Counties.

Flash Flood Warning including Willis TX, Prairie View TX, Waller TX until 9:00 AM CDT pic.twitter.com/mBgCOai4ZH

— NWS Houston (@NWSHouston) April 30, 2021

Over the next few hours, we expect this band of rain to stay mostly in place, though it may wiggle east or west a bit at times. This will allow for repeated rounds of rainfall on the west side of town, and totals could easily jump up to 2 to 5 inches or more in some spots before this evening. East of Houston? You’re fine for now. Expect at least some rain or showers and storms today, but places like Galveston or League City or Baytown will probably fare okay today with modest rain totals.

Tonight

We may see things taper off this evening for a time, or at least become more intermittent across much of the area. But the next round of rain seems likely to develop overnight, particularly to the southwest of Houston. This batch of rain is likely to try and work into parts of the Greater Houston metro toward Saturday morning. We’ll have more on this later today.

Saturday

Many folks have Saturday plans. Between crawfish boils, the MS 150 bike ride, and other post-vaccination life fun, there is a lot planned this weekend. While I want desperately to be an optimist and tell you it’s going to be fine, the reality is that you should have backup plans in place for outdoor events tomorrow. I will say that the afternoon *might* look better than the morning. We expect that area of rain and storms to weave through the area tomorrow morning and hopefully exit to the east or die off. But there are some models that keep periods of moderate to heavy rain going west and southwest of Houston in the afternoon as well. The reality with upper lows is that forecasts beyond 12-18 hours get sloppy, and we won’t have a great idea on what tomorrow looks like until tonight.

Saturday night & Sunday

One more slug of rain and storms is possibly going to move through later Saturday night and Sunday morning. By Sunday afternoon, the focus of rain should shift into far East Texas and Louisiana and Mississippi. Hopefully by Sunday afternoon we will see some sunshine.

Temperatures all weekend look tolerable, albeit with some humidity with highs in the 70s and lows in the 60s. Sunday could see temps surge past 80° with enough sunshine, however.

Next week

Monday looks like a fine day right now. There may be just enough of a trigger left behind after the weekend storm to allow a shower or storm to pop up, but as of today we would expect the vast majority of the region to stay dry on Monday. Heat and humidity will rule, with lows in the 70s and highs in the middle or upper-80s. A cold front still seems on track to hopefully clear the area on Tuesday. It will bring a chance of showers or storms, and then follow up with hopefully a little lower humidity for Wednesday and Thursday. Right now, this still looks promising, but as noted American philosopher Justin Timberlake once quipped, “It’s gonna be May.” May in Southeast Texas is often where cold fronts come to die. Here’s hoping that’s not the case next week.

We will have another update on today’s rain situation before Noon today.

Good evening. We’re getting closer to the first of two rounds of potentially heavy rainfall for the Houston area, and we’ve seen enough data from the high resolution models to raise our concerns. Therefore we’re issuing a Stage 1 flood alert for the greater Houston region. Such a Flood Scale alert, effectively, means to expect the potential for street flooding in the Houston area.

The first period of heavy rainfall will begin after midnight tonight across the Houston area, and the atmosphere is moist enough to produce rainfall rates of 1 to 2 inches per hour, which can begin to back up roadways. Conditions for heavy rainfall will persist into the morning hours on Friday, and possibly into the early afternoon. Our general expectation for rainfall totals during this first round is 1 to 2 inches for most areas, but there will very likely be some bullseyes that receive up to 5 inches or more.

Then we expect to see something of a lull in rainfall from Friday evening into Saturday morning, before round two begins. Storms will probably get spun back up from Saturday afternoon through Sunday morning, when there may be another 1 to 2 inches of widespread rainfall, with more bullseyes. This is all being driven by a slow-moving upper-level low pressure system that is difficult to predict.

We’ve issued this Flood Scale alert tonight, because we think some areas may see heavy rainfall before sunrise on Friday morning. Matt will have a full update for you early on Friday, and will reevaluate our Flood Scale status at that time. Then, of course, we’ll keep tabs on this system over the weekend as needed.

Good morning. The forecast for this weekend continues to evolve and now looks considerably wetter than we anticipated a couple of days ago. This is a dynamic forecast with the kind of weather system that forecasters struggle with. So please be patient with our rainfall predictions over the next few days.

Thursday

Fairly vigorous storms associated with a cold front moved across Central Texas last night, but they are weakening as they move westward toward Houston this morning. So is the front. As a result, today is likely to be warm, with highs in the low 80s, and mostly cloudy skies for much of the region. There will be some scattered showers, but the better rain chances will come after midnight as the front sags into the area and stalls. Low temperatures will not fall below 70 degrees.

Friday

Cloudy skies and showers should limit highs to the upper 70s. Rains should become more widespread on Friday morning across the region, with accumulations of 0.5 to 1.5 inches likely throughout the day. The storms for Friday through the weekend will be driven largely by an upper-level low pressure system, and these are notoriously difficult to predict in terms of rainfall output. This can lead to a boom-or-bust forecast. Some areas of the region may see very little rain, and others enough to flood streets with slow-moving storms. So bear that in mind with regard to this forecast, and the potential for change. Matt and I will be watching this closely, and updating the forecast as needed and as our confidence improves. Lows Friday night will again drop to around 70 degrees as at least some slight to moderate rain chances persist.

Saturday and Sunday

The upper-level low will move more directly over head this weekend and continue to drive the potential for showers on Saturday morning, and then again Saturday night into Sunday. Depending upon how much rainfall the region gets on Friday, these additional rounds of showers may lead to some flash flooding of streets. Overall accumulations from Thursday morning through Sunday will likely be in the range of 2 to 3 inches of rain for most areas, but there almost certainly will be higher bullseyes.

So what does this mean for weekend plans? I know the Bike MS Texas is on Saturday, and at least light to moderate rain is likely along the route. Will there be thunderstorms? I’m less certain about that but it’s a possibility. The bottom line is that, after a string of sunny weekends with sedate weather, we’ll need to pay attention to Mother Nature this weekend. Sunday afternoon offers the best opportunity for clearing skies and lower rain chances, if that helps.

Next week

Rains end and temperatures rise to start next week, with highs likely reaching the upper 80s to even 90 degrees for inland parts of the area. Our next front could push through by late Tuesday or Wednesday, and let’s hope this one makes a clean passage into the Gulf of Mexico, rather than getting hung up over Houston. Right now that seems the most likely scenario.