Matt Lanza

In brief: Houston’s forecast appears mostly on track, with a definite trend toward the heaviest snow and sleet emerging south and east of Houston by Tuesday morning. Accumulations may be as high as several inches under the most persistent bands, with a general coating to few inches elsewhere. Winds will gust near the coast Tuesday morning as well, and a very cold night still looks on tap tomorrow night.

Happening now

Well, our much advertised winter storm is underway across the Houston area. We’ve seen reports of sleet, graupel, rain, and snow across the region. We seem to be settling down into a tiered setup now with snow and sleet north and west, sleet and graupel in the lighter precipitation, and sleet and rain near the coast.

That area of snow and some sleet occurring north and west of Houston is going to gradually fill in and drop south and east through the night. As it does so, we’ll pick up some accumulating snow. As it gets closer to the coast and the potential for banding gets underway, that’s when we may see locally heavy snow anywhere from I-10 southward to the coast.

Forecast for the night

So before 3 AM, look for this potpourri of precipitation types. Again, plain rain should be expected in spots near the coast especially. This is not a surprise and was anticipated ahead of time. After 3 AM, there will be a transition to all sleet and snow and eventually just snow. There is a good chance we will wake up to snow falling tomorrow, although how much on the ground is an open question with a few possibilities. Snow should end from northwest to southeast after 9 AM tomorrow.

Why have we been kind of cagey on snow accumulation numbers?

Those that read us closely can tell we’re throwing out various accumulation numbers based on model data and National Weather Service forecasts but we’re not exactly confident. Now, the event is underway so we should be highly confident, right? Not right. The SREF is a short-range ensemble model, meaning it’s run multiple times with varying snapshots at the beginning to produce a more realistic spread in outcomes. Basically, we want to see how bad or not bad it can get. As of the 3 PM run this afternoon, this model showed snow totals ranging from nada to as much as 7 inches at Hobby Airport.

Now, Hobby Airport almost certainly won’t get 7 inches of snow. It probably won’t get 0.0 inches either. The average on this particular model is around 2 inches, which is reasonable, but there is such a spread in options here that it doesn’t necessarily inspire much confidence. The trouble with this event is that we’re dealing with a wintry mix at the start, we don’t know where banding will establish, we’re in a place that rarely sees weather like this so it’s far outside of the bounds of the climatology (normal) these models use, and we have the Gulf of Mexico in our backyard. All that to say, this stuff is hard. If you want snow, hope for the best. If you do not want snow, hope for the best. May the odds be ever in our favor.

Sleet versus graupel

Here’s a true story. Back in my on-air broadcast days in Utica, NY, I once was describing a day where we had a bunch of graupel fall in Upstate New York and explained what it was. Immediately after the news, I received a call from an older gentleman who told me he had a dictionary in front of him, couldn’t find the word, and proceeded to lambaste me for making up words. I can assure you that it is a real word. So what is it, and how does it differ from sleet?

We’ve gotten reports of sleet and pictures of basically tiny “balls” of ice across the area. When you look at the pictures, however, they look more like Dippin’ Dots than ice pellets (sleet). That’s a tell-tale sign of graupel. The differences? Sleet is straightforward: A snowflake falls, hits a layer of milder air above freezing, melts, and then refreezes in colder air below that, falling as quite literally an ice pellet. Graupel happens when you get water droplets that are still liquid below 32°, (or what is called “supercooled”). The supercooled water droplets collide with and freeze on a snow crystal, a process called riming (which is a homonym of “rhyming”). They basically fall to the ground as snow pellets. They tend to be whiter (hence Dippin’ Dots-like!), whereas sleet is clearer. Sleet melts in your hand, whereas graupel may fall apart or crumble in your hand.

What many of you may have reported as sleet tonight was actually graupel. This is a weird storm because we have a pretty intense layer of dry air from the surface up to about 5,000 feet and from about 12,000 feet up to 30,000 feet. The region of the atmosphere where snowflakes will grow is up above 15,000 feet, so we’re seeing a bit of chaos ongoing above our heads. As the night goes on, this dry air will erode as the atmosphere cools, leading to more regular snow.

Eric will have the latest for you in the morning. Stay safe, stay off the roads tonight, and we’ll see where we are tomorrow!

In brief: There have been few changes to the overall forecast today, with higher resolution modeling now coming into range on this storm and essentially validating most of what we’ve seen to this point. A legitimate, rare winter storm, with primarily snow and sleet is likely to impact most of the Houston area tomorrow night and Tuesday, causing significant travel disruption through at least Wednesday morning.

What’s new?

A few minor notes this afternoon, none of which are significant changes in thinking from this morning.

First off, the NWS has upgraded us to a Winter Storm Warning and increased their snow total forecasts for the Houston area.

They have also increased the “realistic worst case scenario” snow forecast.

Why has this happened? Well for one, modeling has continued to lock in colder with this storm, showing a sharp transition overnight Monday into Tuesday morning from plain rain, freezing rain, and a mix of sleet and snow to just sleet and probably mostly snow across the region. Secondly, high resolution weather models that only run about 48 to 60 hours out in time are now in range of the storm, confirming both that precipitation-type outcome and the potential for “banding” that will exacerbate local snowfall totals.

Again, we have to note: The snow will not fall perfectly uniformly across the region. Depending on where this “banding” sets up, that will determine places that are at risk for 6 inches or more of snow. Quite frankly, that could be anywhere in our area; we simply don’t know at this time. Recent model runs have favored the Houston through Liberty County areas, as well as Brazoria County through Beaumont areas, but that could easily change. I’d say we’ll know more tomorrow, but realistically, we may not know it until it starts.

Again, just to underscore: As long as the forecast stays on track, travel is going to be nearly impossible Monday after midnight and all day Tuesday. You will almost certainly be stuck where you are until at least later Wednesday morning. The exception to this may be the far north now (like north of Highway 105), where snow may end up lighter, no ice occurs, and roads may clear off a bit after the snow stops Tuesday afternoon. But even that may be optimistic. More to come on this.

Historical context

Realistically, this is the most significant snow threat to the region since Christmas Eve 2004. The 1895 storm stands alone as the greatest on record in Texas and Louisiana, and this storm will not dethrone that one. However, with that in mind, this has the potential to set a modern official snowfall record in Houston, which currently sits at a mere 3 inches back in February 1960. January 1940 also sits at 3 inches. While a few storms since then, including Christmas Eve 2004 have produced higher amounts in parts of the area, from a record-keeping perspective, we have a chance to make some noise.

Could it be a blizzard?

This morning I noted how wind gusts of 40 to 50 mph were possible on Galveston Island Tuesday morning with this storm. That obviously begs the question of whether or not this could end up meeting blizzard criteria. That will be hard. The technical requirements are:

1.) Sustained wind or frequent gusts to 35 mph or higher. (This will be close)
2.) Heavy snowfall or blowing snow that reduces visibility under a quarter mile. (This will be tough)
3.) Three consecutive hours of these conditions. (This will be very tough)

I’m not saying it can’t happen, but given how rigorous these requirements are, I have doubts that we’ll officially get there. But at least now you know what an official blizzard is. That said, we almost certainly will see blizzard-like conditions on the island if those winds come to fruition and a full changeover from sleet to snow occurs.

Whatever the case, we are into some seriously rare winter weather for Houston in what may end up being a generational winter storm. We will have the latest for you in the morning with revised model data at our fingertips.

In brief: A major winter storm continues to look likely for the Houston area Monday night and Tuesday, with the potential for heavy snow and sleet in parts of the region. Minor ice may occur near the coast, along with windy conditions. Travel will become difficult to impossible Tuesday morning and remain that way through at least Wednesday morning across most of the area. A significant, damaging freeze is likely Wednesday morning as well. We do warm up Thursday.

Current cold

If you’ve stepped outside, or like Eric, started running the Chevron Houston Marathon, you know it’s, um, cold.

Speaking of which, let’s check on Eric as of 8:40 am! Good luck to Eric the rest of the way!

Temperatures will recover some today, getting up into the low or mid-40s. Another cold night is expected tonight, with lows in the 20s across most of the area away from the coast. Expect a hard freeze for many outlying areas and some areas in the city too.

Remember the basic preparations you should be taking.

• PLANTS. Protect tropical vegetation. Please note, with temperatures dropping this low, some vegetation will probably die regardless.
• PIPES. Protect any exposed outdoor pipes. Pipes in attics and along exterior walls of structures could freeze at these levels.
• SPRINKLERS. Sprinkler systems should be shut off and properly drained.
• ANIMALS. Prepare proper shelter and warmth for animals and livestock and make sure water sources are not frozen.

And also remember to check on people that may not have adequate insulation or access to heating.

Monday

Most of tomorrow should be fine. We will see increasing clouds that may hold temperatures back a bit. Highs should be in the upper-30s. Precipitation begins sometime either Monday afternoon or evening. With temperatures comfortably above freezing, whatever falls initially may be a light rain. Resist the urge to call bust.

Sidebar: The air mass over us will be quite dry. This is important. As the rain begins falling on Monday afternoon and evening, it may fall as virga (rain that does not reach the ground). But as it evaporates on the way down, it will cool the entirety of the atmosphere from a few thousand feet up to the ground. This is essentially priming us for snow and sleet. So initially, it may fall as rain, but that will change Monday night.

The best advice we initially can offer: Be where you need to be by early Monday evening and prepare to be stuck there through at least Wednesday morning.

Monday night and Tuesday morning winter storm

As the precip increases in coverage and intensity and temperatures drop, we will see a changeover from rain to a mix of sleet and snow. I have to be honest: Much of the model data seems to be favoring a gradual change from sleet to mostly snow, especially along and north of I-10. South of there, it should still be a mix of sleet and snow, with potentially a little freezing rain near the coast or Matagorda Bay area.

A couple notes about how things will unfold.

• This storm has been strongly signaling what we call mesoscale banding or the potential for a deformation zone. In plain language? There will be widespread snow and sleet, but embedded within that will be a couple corridors of heavy snow. Those bands can see quick, heavy accumulation and snow rates of 1 to 2 inches per hour, along with the potential for thundersnow.
• That banding will also lead to a disparity in snow totals. You could, in theory, have an area that sees 2 to 3 inches and literally down the road an area that gets 6 or 7 inches.
• Sleet is the biggest risk to all this. If we end up with significant sleet and less snow, accumulations will be much lower — but travel will be just as bad. Models are trending toward more snow over sleet for much of the region, but admittedly, this is not an area where models handle things super wonderfully.
• Wind will howl on Tuesday morning, especially on Galveston Island, where gusts could exceed 40 to 45 mph. Inland gusts will be to 20 to 30 mph. Coupled with areas of heavy snow, this will create extremely poor visibility and potentially some blowing and drifting of snow. Yes, that’s an actual sentence I just typed for Southeast Texas.

When all is said and done, how much snow will you get in your backyard? The official NWS forecast is shown below.

I will say that the risk is probably asymmetrically skewed to the higher side here. In other words, there is a chance of more snow than shown, but again it will depend on sleet and exactly where those “mesoscale bands” setup. Max totals could be, could be as high as 6 to 8 inches. But those will likely be the exception, not the rule.

How about ice? Well, the official NWS forecast is one that isn’t overly bullish on ice, which is good news. Ice is where you can start to have more meaningful issues with infrastructure issues (trees, power lines, etc.). Ice of this amount would make conditions a little extra slippery but be unlikely to cause damage.

The highest ice totals are likely to be south of I-10 and in the Victoria Crossroads back toward south of San Antonio.

Travel concerns

There’s no real good way to get around this: We are inherently unprepared for a major snowstorm because, well, it rarely ever happens. Thus, you can expect that travel will be difficult to perhaps impossible on Tuesday, probably Wednesday morning, and maybe even Wednesday afternoon. We really cannot underscore this enough: Barring a dramatic forecast change, tou will probably not be able to get very far in a vehicle Tuesday or Wednesday morning. Your flight will probably be cancelled. Prepare to be stuck where you are after Monday evening.

Wednesday morning hard freeze

With ideal conditions for cold weather, including fresh snow on the ground, you can expect Wednesday morning to be very, very cold. While it won’t be super cold across the rest of Texas, locally here in Southeast Texas, we may rival one of our coldest mornings of the last few years.

Expect lows in the teens virtually everywhere away from the coast. Areas that see minimal snow accumulation will also likely be milder. This will be a hard, damaging freeze and maximum cold weather precautions need to be taken.

Wednesday afternoon should see sunshine but with snow and a bitter cold start, we will likely only get into the mid-30s or so. Another hard freeze is possible Wednesday night, albeit much less cold than Wednesday morning. And we should bounce back into the 40s on Thursday. Alas, the snow will melt.

Anyway, we’ll update you on any changes later this afternoon. But hopefully this post answers most of your questions in the meantime. Stay warm!

In brief: A complicated winter storm for Houston next week continues to give us fits in weather modeling, with today’s flavor being the potential for more snow and sleet than anything else. However, we expect the forecast to continue changing over the weekend and will keep you posted. Either way, travel across the Houston area may become very difficult Tuesday and Wednesday.

Winter storm update

What has changed since yesterday? Well, a lot. The storm is back. But this time it’s a bit colder overall, which means perhaps more in the way of snow and sleet than ice. That would be good news. That said, there remains a ton of uncertainty. As a native of New Jersey and having cut my teeth forecasting in Upstate New York, I have learned to never take a winter weather forecast from models literally. This is doubly true in the South where snow and ice are generally outside the bounds of climatology, which tends to give models fits and leads to us having to caveat every single thing we say.

Anyway, here’s the NWS National Blend of Models snow forecast for the last several runs. This incorporates a bunch of models and weights them. You can see a lot of fluctuation in outcomes here.

What are we confident in? The timing. Precipitation should begin, lightly on Monday afternoon or evening. The height of the storm would likely be from about 4 AM to Noon Tuesday, with conditions slowly improving Tuesday afternoon. We are also fairly confident that Wednesday morning should be the coldest morning next week. A tropical-plant damaging freeze is likely on at least one or two mornings. An irrigation system damaging freeze is also likely if precautions are not taken.

What are we not confident in? How much of what falls where. While the models have brought the storm back into the forecast since yesterday, they remain a bit split on exactly how it plays out. We can say that in general today, it appears the highest odds of snow are north and east of Houston and the highest odds of ice are south of Houston and near the coast. Beyond that? We can’t say much. Unfortunately, that’s the most important question to answer in terms of travel conditions, school closures, etc. We will get some confidence on this through the weekend. We would think that by the morning of the MLK holiday, decisionmakers will have enough to work with.

What else aren’t we confident in? How cold it gets Wednesday morning. Snow cover is a significant component of what we refer to in meteorology as “ideal radiational cooling,” the premise being clear skies, light winds, and snow cover all contribute toward an ideal scenario for cold weather. Without snow cover next week, we’ll likely see mostly 20s for lows with a few teens north. Cold for sure, but nothing extreme. However, let’s say we get 2″ of snow across Houston. Then we could easily shave an additional 5 degrees off that, nudging us into the teens everywhere except the coast.

So there is a lot to unpack here still, and over the next couple days we should begin to see clarity. Eric and I will keep you posted on all that as it evolves with regular updates through the weekend.

Houston Marathon

I admire anyone that runs a marathon. I especially admire anyone that does so with temperatures in the 30s and a north wind gusting up to 25 mph or so. That’s what we have for you on Sunday. Temps will rise a little through the run, possibly getting to near 40 degrees by the end, but either way, it’s going to be very cold. Good luck to Eric and to all those participating in the run(s) this year!

Rest of the forecast

For those of you with weekend plans, there could be an isolated shower this afternoon or tomorrow afternoon as the front moves in, but otherwise it looks dry. Temperatures will peak in the upper-60s or low-70s today, so bust out the shorts and enjoy! Tomorrow will likely get into the 60s before the front hits in the afternoon. Temperatures will then fall tomorrow evening through the 50s and 40s and into the 30s in most of the area, with some 20s in more rural spots north of I-10 by Sunday morning. Sunday gets up to the low or mid-40s, maybe and looks windy and cold.

Monday will start in the 20s and warm into the upper-30s to low-40s. Depending on how the storm evolves, look for lows in the upper-20s and highs in the low or mid-30s on Tuesday with a breeze as well. Wednesday will probably get up near 40, but as noted above, there is some uncertainty on how cold it gets in the morning. And then a more proper warm up ensues for later next week.

Again, we will keep you posted regularly through the weekend on next week’s cold and potential winter precipitation.