Eric Berger

In brief: This evening’s update celebrates Houston’s first snow day in a long time, when nearly everyone did the right thing and stayed home. With a very cold night on tap we need to hang tight for a little while longer before things warm up on Wednesday.

Houston has a snow day

Y’all did amazing today. The city of Houston, alone, has more than 16,000 miles of roadway. One could drive nearly two-thirds of the way around the world in that distance. Most of those roads were iced over today with snow, sleet, slush or some other wintry mess. And according to the Houston Police Department, there were just 22 accidents today. That’s a testament to all of the people who stayed home, all of the employers who made the painful decision to close their businesses, and every other organization that stood down today. It was a special day, a true snow day, and we’re unlikely to soon forget it.

But we’re not yet done. We need everyone to stay home again this evening, tonight, and early Wednesday morning before we thaw out for real. More on the timing of this below.

How cold tonight?

I would not gamble any money on making a temperature prediction tonight. I believe most of the region will fall into a range of about 18 to 28 degrees, and it will vary widely due to a number of factors, including snow cover. Regardless, it will be the coldest night of the Arctic outbreak we have experienced so far. For reference, temperatures generally fell into the upper 20s on Monday night in Houston. So if you’re worried about pipes, this is the night for maximum preparation.

Timing of Wednesday warm-up

I’ve been watching Houston Transtar’s cameras today, and just before sunset many of the area’s freeways still looked wet. That water is going to freeze tonight. A lot of Houston’s feeder roads and side streets, which got slushy or melted on Tuesday afternoon, are going to freeze tonight. There is a phenomenon known as black ice, which occurs after snow melts on roadways and then re-freezes. This is a thin sheet of ice that, because it is transparent, may not be readily visible to drivers.

All of that to say, some of Houston’s roads may have dried up today. But many of them did not, and they will be slick tonight and on Wednesday morning. For your safety, it would really be best to preclude any travel tomorrow before late-morning. Some time between 10 am and noon air temperatures will rise above freezing, and in concert with sunny skies this should act to fairly quickly melt remaining ice on Houston’s roads.

Mobility around Houston should rapidly improve during the afternoon hours on Wednesday, with high temperatures climbing into the 40s.

Our next update will come at the usual time, on Wednesday morning. Stay warm, y’all. We’re almost through this!

In brief: A winter storm has brought a mixture of precipitation to Houston overnight, including snow and sleet. This wintry precipitation will end later this morning, and we will see some sunshine and above-freezing temperatures this afternoon before a very cold night.

Storm status

The Houston region has received a mix of snow, sleet, and other forms of wintry precipitation during the overnight hours, setting up slick conditions on Houston area roadways. Total snow amounts have varied widely, from a fine dusting of ice and sleet in some locations to 3 inches or more elsewhere.

Additionally, it is quite cold outside this morning. Air temperatures are generally in the mid- to upper-20s for most of the Houston region. However the addition of brisk northerly winds, gusting up to 25 or even 30 mph from the north, have made it feel like it is in the teens outside.

With temperatures now well below freezing for much of Houston, what is falling is largely sticking to area roadways that have been untreated with salt. There are dozens of reports of ice on area freeways, feeders, and major roadways, some of which are shut down. You can track an list of Houston-area icy roadways on Houston Transtar.

In short, for some areas it is a winder wonderland outside, for some a sleet-fest, and for all a dangerous time to be outside. Please do stay home this morning if it is at all possible.

Tuesday

The latest modeling indicates that the precipitation we are seeing this morning will exit to the east by 9 or 10 am CT. We should then see some clearing skies early this afternoon across Houston, including the coast by later this afternoon. This sunshine should push temperatures toward the upper 30s, allowing for some of the ice and snow on the surface to melt.

Additionally, the combination of sunshine and windy conditions (from the north at about 15 mph) should begin the process of sublimation. Sublimation occurs when snow transitions directly into water vapor, without first becoming liquid water. I’m writing all of this because it is possible that some roads will become clear and dry this afternoon, especially for locations further from the coast where there will be a longer period of sunshine to work with.

This matters because temperatures are going to freeze again tonight. So if there is moisture on roads, it will freeze into ice tonight, and into Wednesday morning. This could lead to black ice or situations in which there are patches of icy, dangerous roads tonight.

The temperature tonight at your location will depend on how much snow cover remains. That’s because new snow has a very high albedo (up to 0.95 out of 1), which means it is highly reflective of heat (radiation) back into space. So locations where there is a snowpack tonight will be 5 or 10 degrees cooler than areas with “darker” surfaces not covered by snow.

Over the last couple of days we have watched as forecast models have really struggled with how cold temperatures will get in the Houston region on Wednesday morning. As a best guess, areas with a layer of snow may drop into the mid-teens tonight, and areas with less or no snow are likely to only fall into the mid-20s or so. My sense is that most of Houston probably will end up in the lower 20s, but we shall see.

Wednesday

After a cold start, high temperatures on Wednesday are expected to reach 40 degrees or even a little warmer under sunny skies. The combination of mostly sunny skies and sublimation should allow for roads to mostly dry out, but for some locations this may not happen until after noon. I realize the uncertainty is no fun, but such snow and ice events are relatively rare in Houston, so we are working on limited data about local roads and their response to icy conditions. Most of Houston will fall into the upper 20s on Wednesday night.

Thursday

A little warmer, with highs generally in the upper 40s to go along with mostly sunny skies. A light freeze is likely Thursday night.

Friday

Expect more sunshine, with highs in the 50s. Some inland areas may see a light freeze on Friday night, but most of us should be in the mid- to upper-30s.

Saturday and Sunday

Expect highs in the 60s this weekend, with nights only in the 50s as a warmer pattern returns. Saturday looks OK for outdoor activities, but rain chances start to increase by Sunday into next week.

Update schedule

We will have an update for you early this afternoon, by 2:30 pm CT, and again this evening to offer the best possible forecast for temperatures and roadways on Wednesday morning.

In brief: We are fast approaching the arrival of a winter storm, which is likely to begin with freezing rain or sleet late on Monday, and transition to snowfall early on Tuesday morning. Although we still have some questions about the details, there is little question that large chunks of Houston are going to get frozen in on Tuesday due to icy roads.

The coast with the most

One of the emerging trends we’re seeing in higher resolution models today is a greater concentration of snow in coastal areas, including Brazoria, Galveston, and Chambers counties. Matt mentioned the possibility of blizzard conditions tomorrow on Galveston Island, and I think it’s distinctly possible. Winds are going to peak between midnight and noon on Tuesday, with gusts likely above 35 mph. When you add the likelihood of heavy snowfall, you have the potential for a once-in-a-lifetime winter storm on the upper Texas coast.

How much snow will I get?

Snowfall forecasts are really difficult. Why? Because 0.1 inch of precipitation in rainfall equates, roughly, to 1 inch of snow. So relatively small differences in total precipitation lead to rather significant differences in snow accumulation. With that in mind, it does look as though the majority of the Houston area is likely to at least see at least 1 to 2 inches on Tuesday between midnight and noon. But totals could run much higher.

There likely will be a band of heavier snow, perhaps up to 6 inches or even a little more. I think it’s more likely this banding effect sets up near the coast, or possibly even just offshore. However, it could also line up along Interstate 10. Areas further north, including The Woodlands and College Station, appear to be less likely to get multiple inches of snow on Tuesday.

How cold will it get?

One area in which the models are really struggling is how cold air temperatures will get on Tuesday night and Wednesday morning. There remains a wide variance, and most locations in Houston may get as cold as 15 degrees, or remain relatively warm, in the upper 20s. Some of this variance is due to how the models are handling snowfall totals. In any case, we will try to refine this forecast in coming updates.

When will we thaw out?

Most of the model data continues to indicate that high temperatures will reach about 40 degrees on Wednesday. This, along with ample sunshine, should help to melt and dry out our roadways. If moisture remains on Wednesday night, then it is likely to re-freeze on Thursday morning. However at this time my best guess is that roads are OK beginning Wednesday afternoon, and onward. But it’s something we’ll keep an eye on.

How historic is this?

I’ve been writing about weather in Houston for a quarter of a century, and I’ve never seen a winter storm setup like this. Parts of the region saw several inches of snow back in December 2004, but it was mostly a coastal event, with much of Houston seeing flurries at most. We probably have to go back to 1895 to find an winter storm event that exceeds what the region is likely to experience on Tuesday.

Update schedule

Our next update will come this evening, no later than 10 pm CT. Then we will have full coverage for you on Tuesday, starting before sunrise. Please be safe and warm!

In brief: Houston is less than a day away from the onset of a winter storm that is likely to cripple transportation around the region. We’re still expecting primarily snow, with impacts on roadways through Wednesday morning. Expect two additional updates today on Space City Weather as we share what we know, when we know it.

Cold update

As anticipated, temperatures this morning have fallen a couple of degrees below freezing across the metro area. Fortunately, you still have today to prepare for a winter storm that will very probably bring more snow into the Houston region than we have experienced in at least two decades. The city is likely going to shut down from this evening through Wednesday morning, and it really should do so because we are ill-equipped to handle this kind of winter storm.

Before jumping into the post, I also want to thank the organizers of the Houston Marathon, as well as all of the thousands of volunteers and tens of thousands of spectators who make this such a special event. Yes, it was cold on the course on Sunday, but honestly after a mile or two the colder air felt great. It also feels great to be able to set aside my running shoes for awhile.

Monday

It is MLK Day, which honors the legacy of the civil rights leader Martin Luther King Jr. For kids, it’s a day off of school which, in addition to ‘snow’ days on Tuesday and Wednesday, makes for a five-day weekend. Not bad. It’s almost enough for me to wish I was seven years old again. Almost.

Anyway, today will be a brisk day with increasing clouds and high temperatures of around 40 degrees. A gusty easterly wind will add to the misery. We’ll see a slight chance of showers by around sunset this evening, but for the most part this should be rain in the Houston metro area. Please do plan to be wherever you’re sheltering from the storm this evening by about 8 pm for northern areas such as The Woodlands, and midnight at the absolute latest for central and southern parts of the Houston area.

Monday night and Tuesday

By around midnight temperatures in the region will reach freezing for most of Houston, and light rain will begin to transition to snow, sleet, and possibly freezing rain. The intensity of these snow showers or sleet will pick up on Tuesday morning. Low temperatures will drop to between 25 and 30 degrees for most of the region.

So what will you wake up to? I anticipate that most of the area will see 1 to 4 inches of snow, with some sleet mixed in by mid-morning on Tuesday. We still have some serious questions about the amount of precipitation, and I agree with Matt that there is a decent chance that some parts of Houston receive up to 4 to 6 inches. (Currently the favored region for this is probably along and south of Interstate 10, but we shall see). In any case, this should be wintry setup for which Houston-area roads are not prepared for.

Temperature wise, Tuesday is going to be interesting. The precipitation will end by around noon, and I expect we’ll see clearing skies during the afternoon hours. Temperatures will probably briefly get above freezing during the afternoon hours, and this may cause some of the snow and ice on the roads to briefly melt. However this window will be brief, as temperatures drop to below freezing by around sunset again. It will be a very cold night with slick streets.

Wednesday

How cold will it get? That will depend on the extent of snow cover where you are. I think most of Houston will fall to around 15 to 25 degrees, so a hard freeze all around expect perhaps for the immediate coast, such as Galveston Island. Air temperatures will likely reach above freezing at some point on Wednesday around noon. Then, sunny skies and temperatures in the upper-30s, at least, should help to clear roadways during the afternoon hours. By this time it should be possible to resume somewhat normal activities around the region. But we’ll need to see how the mobility situation plays out.

Thursday and beyond

Lows on Wednesday night will drop into the mid-20s in Houston, so another cold night. However by Thursday afternoon we’ll be well into then 40s. A light freeze is possible again Thursday night. The weekend looks mild, with temperatures climbing back into the 60s. A chance of rain returns by around Sunday, or so.

Best sledding in Houston

It’s kind of insane, but we’ve reached the point where we can legitimately talk about sledding here. Now Houston is a pretty flat city, so there are not a lot of great hills. But there are a few, such as the hill at Miller Outdoor Theater in Hermann Park. However, when choosing a locale for sledding on Tuesday (and possibly Wednesday) it would be foolish to choose a spot you have to drive to. Since we’re not going to be driving around on Tuesday, are we? In reality the best place for you to sled in Houston the steepest hill you can walk to.

Which doesn’t lead down into a pond or a bayou.

Update schedule

We plan on having two additional updates today. One will come this afternoon, probably around 3 or 4 pm; and another later this evening when we should be able to provide real-time information on the developing winter storm.