Matt Lanza

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.

The main story in today’s post will be regarding the chance of strong to severe thunderstorms today. The Storm Prediction Center has most of the Houston area in a “Slight” risk (level 2/5) of severe weather today. Areas around Lake Livingston and Crockett are in an “Enhanced” risk (level 3/5) of severe weather.

Let’s walk through what to expect.

When will it rain?
We are already seeing a few showers across the area, with some localized downpours east of I-45 and lighter showers or light rain and drizzle elsewhere. Look for the coverage of showers to increase through the morning and continue off and on through at least mid-afternoon. It will not rain all day, and it may not even rain everywhere. But that chance is going to hang with us all day today, so it’s best to have an umbrella at the ready wherever you go. A second round of showers or storms is possible this evening, but confidence in what that exactly looks like is low. Rain chances will drop off and eventually end overnight after a cold front pushes through toward morning.

When is the best chance for severe weather?
There will be two chances at severe weather today. The first will be with a warm front lifting north across the area from late morning into early afternoon. That could produce individual thunderstorms capable of producing large hail or an isolated tornado. The relative highest odds of that occurring would be north of I-10 and east of I-45, particularly as you get closer to that “Enhanced risk” area northeast of Houston. The second opportunity will likely come with the “dryline” sweeping east late this afternoon or evening. Severe weather may occur in Central or North Texas as individual cells develop, eventually probably congealing into more a squall line and general strong, damaging wind threat as it sweeps east.

There is still a bit of uncertainty regarding exactly how things will play out today, but if it looks more serious closer to the Houston area we will keep you posted.

Will there be tornadoes? Hail?
As is often the case, the odds of any one location seeing significant severe weather today is quite low. But that said, hail and damaging winds will be the primary threat from today’s storms. But, yes, there is at least a chance for an isolated tornado, particularly with the late morning and early afternoon storms that develop mainly north and east of Houston. The best hail odds today will be with the storms developing in Central Texas, especially initially. As those approach the Houston area this evening, I would expect the hail threat to diminish and transition more to a damaging wind one.

When will it end?
There will probably be a lull late this evening or early in the overnight. A brief shower or storm can’t be entirely ruled out late tonight or very early Saturday morning as the cold front approaches. But for the most part, the rain chances and severe weather risks will end after this evening.

How much rain should we expect today?
It’s likely that rain totals are wildly variable across the region today. It’s possible some places see merely a few hundredths or a couple tenths of an inch of rain, while others could see 2 to 3 inches or more. The current NWS forecast is below.

The more sustained storms north and east of Houston will likely allow for heavier rain, so those areas have the highest odds of seeing 1 inch or more. Areas south of I-10, where storms may struggle to get going this morning stand the best odds of seeing a quarter-inch or less. Some of our higher resolution models show some serious rainfall gaps south of Houston, with some places seeing next to no rain and others seeing almost an inch. So it’s going to be a roll of the dice today.

Weekend

For those able to enjoy weekends, you’re in for another winner. Saturday will see any lingering clouds in the morning quickly give way to sunshine. Saturday will start off quite warm and very humid. The front should sweep through mid-morning, and that will allow the air to dry out a bit. Drier air tends to heat up faster, so we should easily reach the mid-80s Saturday afternoon. I wouldn’t be entirely shocked to see some upper-80s out there either. At least the humidity will be dropping through the day.

Drier air tends to cool off faster too, so expect temperatures to drop quickly under clear skies Saturday evening into the 60s and eventually the 50s in spots.

Sunday looks warm as well, with highs in the lower to middle 80s and plentiful sunshine again. Humidity will remain low.

Early next week

Look for onshore flow to kick back in pretty effectively on Sunday night and Monday. You’re probably going to notice the wind kick up as well later Monday into Tuesday. Winds will probably gust to 30 mph at times, especially near the coast. We should see more clouds, more humidity, and maybe some light rain, drizzle, or a few showers. Nothing really substantial is expected through Tuesday night, however.

Later next week

Our next front is coming next week — sometime. Right now, the GFS model is bringing the front through on Wednesday night, about 12 to 24 hours faster than the European model. So we’ll split the difference and pencil in a front for later Wednesday or early Thursday right now. That should set temperatures back to comfortable levels for late April once again for a couple days. Enjoy it while we have it around!

Some storms sped through northern parts of the metro area yesterday evening, delivering a few quarter-size hail reports and some locally heavy rain in northern Harris and Montgomery Counties.

@mattlanza pic.twitter.com/DVIPrIOyN2

— Mrs. Pesz (@KristinPesz) April 16, 2021

We’ve got a very unseasonably cool air mass trying to make inroads to Texas right now, so that’s a good recipe for hail. And in fact, today there is a chance of some additional storms with potential hail as well, primarily north of Houston.

Today

Our incoming cold front will slowly drop south across Texas today. A weak system in the upper atmosphere will slide west to east across the state as well. As the front drops in, this should allow showers and storms to break out through the day. The best chance of rain will be north of I-10 once again today. Areas along Spring Creek saw upwards of one inch of rainfall yesterday, so any storms will be capable of dropping some locally heavy rain this afternoon as well.

Those that don’t see storms today will just see clouds and a few showers. It will be fairly warm and humid today as well, with highs reaching into the mid-70s.

Tonight

While this will be a fairly strong cold front for April, it won’t pack a ton of punch as it moves through. I’d expect a narrow line of showers and perhaps some storms along the front to drop through the region from northwest to southeast after 6 to 8 PM this evening, reaching the coast by midnight or so. Expect a gusty north wind to kick in once the front passes, with gusts of 15 to 20 mph possible; a bit stronger over the water. Temperatures will drop back into the 50s to near 60° over much of the area by morning.

Saturday & Sunday

For lack of a better word, tomorrow looks a bit dreary. Right now, forecast highs for Saturday are in the mid to upper-60s, but I suspect that with clouds locked in, cool air pouring south, and some lingering shower chances, we may struggle to reach 65° tomorrow afternoon in much of the area. If that does happen, it would be our coolest late April daytime high in seven years. There will be continued upper level “energy” overhead allowing us to keep mention of shower chances in for Saturday afternoon. Unlike Friday, the best odds of rain tomorrow will be south of I-10 and along the coast. Accumulations should be rather light overall, but it may be unpleasant at times south of Houston tomorrow afternoon.

On Sunday, expect a mix of clouds and some sun, less of a breeze, and continued cool temperatures. Look for morning lows in the 50s (perhaps some 40s north and west) and daytime highs again in the middle to upper-60s.

Next week

It sure looks nice for much of next week. Like, really, really nice. Goldilocks weather: Not too hot, not too cold. Expect a mix of sun and clouds most days. Through Wednesday, high temperatures will top off in the 70s after starting the day in the 50s (with even some 40s possible north of Houston).

There should be a reinforcing cold front late Tuesday night or Wednesday that comes through with little fanfare but locks back in comfortable weather for the back half of next week. Warmer weather and increasing rain chances would follow suit Friday or Saturday.

Easter weekend is upon us, and with many folks planning to take their gatherings outdoors this year, we want to try and pin this forecast down as precisely as possible for you to plan around. In a nutshell: We don’t expect any significant weather at all this weekend, and you should go forth with your plans unaltered due to weather. But there will be just enough of an annoying chance of some light showers later on Sunday.

Today

Skies will start off mainly clear today with ample sunshine. Look for that to continue with just a few high clouds passing through at times later today. It will be another very pleasant, temperate day, with highs in the 60s to perhaps near 70 degrees.

Saturday

Tomorrow won’t be the worst day ever, nor the best day. Look for a good deal of clouds sprinkled with breaks of sunshine. A weak disturbance could squeeze a little virga (rain that evaporates before reaching the ground) out in the afternoon, but for the most part I think Saturday will be fine for all our outdoor plans.

Temperatures will warm from the 40s or 50s in the morning to 60s in the afternoon, held down a couple degrees due to clouds. A few spots could break into the 70s with enough sunshine.

Easter Sunday

We will once again see a good deal of clouds and breaks of sun for Sunday. The forecast has become relatively tricky here, with another disturbance pivoting through and a little more moisture available than on Saturday. The odds of any one location seeing rain is fairly low. But I do believe some locations will see a shower on Sunday. So, the best advice we can offer right now is to go forth with your plans as scheduled, but you may feel some “spritzes” out there Sunday afternoon. By no means will it be enough to wash you out for the day, but it may be enough to be annoying in a few locations.

Temperatures on Sunday should start in the 50s and work their way to about 70 degrees or so. If it does rain in your neighborhood, temps could drop back into the 60s for a few hours.

Next week

We begin to turn the corner back toward warmer, more humid weather on Monday. Highs should top off in the 70s, with morning lows in the 50s once more. A shower is possible with a mix of sun and clouds.

By Tuesday, we’re starting the morning in the 60s and reaching well into the 70s, if not low-80s. Wednesday looks even warmer, with morning lows in the mid to upper-60s and highs in the mid-80s. We should see a typical spring pattern of morning clouds giving way to afternoon sunshine and a token 10 to 20 percent chance of a shower.

Even warmer weather looks possible later in the week, with maybe a weak front in there at some point between late week or early the following week.

Can we hit 90 degrees next week?

Last year, we hit 90 degrees for the first time on March 25th. In 2019, we did it on April 9th. Typically, we don’t reach 90 for the first time until May 7th (though since 1990, that date has moved up to May 1st). Yes, we could hit 90 degrees next week or weekend. As of right now, the European ensemble is projecting that the air mass over Texas by late next week or next weekend (Friday shown here) will be about 10 degrees or more warmer than normal.

We start to see average high temperatures get close to 80 degrees next week, so it becomes simple math at that point. Given the dry soils and growing drought over most of Texas, this will not be a Herculean task. There are still some question marks Depending on your point of view, that’s wonderful or the worst news ever. Either way, it is what it is, and we’ll update you on things Monday!