When it comes to arctic blasts like the one we're going to experience early next week, the jet stream rules the game in the department of snow potential. Will it snow? While it can't be ruled out, it's highly unlikely. But, there remains the slightest chance for light snow or flurries as the coldest air of the winter descends upon Houston next week. Here's a tidbit your automated weather app will never be able to tell you unless a human meteorologist authors it...
In the journey to foresee the future, one must first understand how the jet stream works. It's a river of air that can blow over 200 mph at an altitude of roughly between 25,000 and 35,000 feet. It effectively separates the air masses: arctic cold stays north and the subtropical warmth stays south. If something disturbs the normally west-to-east orientation that keeps Texas warmer in the winter than Montana, and instead sends the jet stream barreling into Houston, that polar air will surge over the warmer water of the Gulf of Mexico at an angle which encourages spin. That spin can result in a surface-low and a snowstorm can form. We've seen this a handful of times over the last 100 years in Houston, but that's not in the cards this time.
More commonly and what we could see is the jet stream acting to usher a little hard-to-see upper level storm system into our region, causing a few snow showers. These little zippity-do-dahs ride the, "wind river" jet stream like a raft bumping down the rapids. When they pass over an area, a rising-motion in the atmosphere can result and build clouds. If these clouds get laden with enough moisture (like from the Gulf of Mexico) precipitation results.
This time of year when the jet stream is overhead, it's often cold enough to snow. Jet disturbances are usually the cause of these, "surprise" wintry events. They seem to always come unexpectedly because these, "rafts" can disguise themselves in the flow as just another blip, when in fact, they prove to be much more.
The computer models have been hinting -- not screaming -- that we may see a few flurries either New Years Day Monday or Tuesday. It'll certainly be cold enough. On occasion, the 4-times daily weather model forecast runs have produced significant, accumulating snow! However, that's not in my forecast. The reason being, there's not enough consistency which leads me to believe if any micro-systems do try to ride down on the jet stream, they'll be too weak to materialize into anything big.
That said, the orientation of the jet stream relative to Texas on the first two days of 2018 is such where we'd be in a favorable area should one of these micro-systems sneak in.
The only most likely slick travel we'll see is due to quickly-falling temperatures on New Years Eve (Sunday night) as the cold front blows through, causing a little icing on still-wet bridges from earlier weekend rains. Because of this, the TX DOT is actively salting these areas right now, just in case. They are playing it safe considering that a few weeks ago when it snowed an inch, and the entire elevated portion of the West Loop (I-610) was shut down due to slick conditions.
Finally, adding to the unlikely snow scenario: since 1895 there have only been five winters where we've had two or more snowfalls in the same season. That alone adds to the already unlikely possibility. If it snows, it'll be a miracle but a reminder as to why you still need a trained human to interpret all this computer model data.