Eric Berger

Good morning. Today is the last day most of the Houston area will see above-freezing temperatures until Wednesday. We have a section at the end of this morning’s post about preparations for the upcoming hard freeze, this really is your last opportunity to do so. After today, Houston’s weather is going to be full on winter until at least Friday.

We’re going to discuss this in three phases: Winter storm on Sunday night into Monday, Extreme cold on Tuesday morning, and a Second Arctic front on Wednesday through Friday morning.

Sunday and Monday

Today will be far from pleasant, but for most of Harris and surrounding counties, temperatures through at least the early afternoon should remain above just above freezing. Additionally, any precipitation that falls before around 4 to 6pm this evening should do so as rainfall. (Note: you don’t have to get too far west of Katy, or too far north of Conroe, before you run into freezing rain today). By late afternoon or early evening, temperatures should begin to drop below freezing across the area, from west to east as an Arctic front moves into Houston.

This front will have two immediate effects. From sunset on Sunday to sunrise on Monday, temperatures will plunge into the low 20s across the metro area. And it will bring a healthy dose of precipitation to the region. If this were to fall as rain, it would be about half an inch for most locations, but due to the cold temperatures, we’re going to see some form of winter precipitation. But what kind? We talked yesterday about how, for snow to reach the ground, temperatures must remain freezing from the surface all the way to clouds where precipitation forms.

On Sunday evening, the atmosphere is unlikely to be below freezing all the way up, so I think most areas will see a glaze of freezing rain fall before it turns to snow. We’re now reasonably confident that areas north of Interstate 10 will see on the order of 1 to 4 inches of snowfall by around mid-morning on Monday. We’re less certain what will happen closer to the coast, where there may be enough lingering “warm” air from the Gulf of Mexico to produce sleet or more freezing rain rather than snow.

The forecast models now suggest this precipitation will end by mid-morning, as the atmosphere dries out. We still can’t have complete confidence in what area roadways will look like, but the potential for a glaze of ice on the surface, covered over by snowfall, is a rather dangerous one. You should be prepared to not go anywhere from Sunday evening through Tuesday morning. Some major roadways may be cleared by authorities, but this kind of winter storm is unprecedented in recent decades because temperatures on Monday will not get high enough to melt roads. Rather, daytime temperatures will remain in the low to mid-20s. So anything that falls, will stick.

Monday night and Tuesday

We still have lots of questions about the severity of cold weather on Tuesday morning, but if the snowfall forecast verifies for Houston it will amplify the cold weather. The combination of snow cover, light winds, clearing skies and an Arctic air mass is pretty much about the most ideal conditions you could conceive for cold temperatures in Houston. However if the region gets more sleet or freezing rain, and clouds linger, temperatures could be somewhat warmer.

As a result, I think we’re looking at a range low temperatures from 5 to 15 degrees for western Harris County and Montgomery County, 10 to 20 degrees in central Houston, and 15 to 25 degrees along the coast. As Matt discussed yesterday, this would be a historic cold snap for the region.

Another question we have is where temperatures may briefly rise above freezing on Tuesday. The coast is a definite yes, where highs may reach the upper 30s. Many areas south of Interstate 10 may briefly see highs of 33 degrees or slightly warmer. I do not know whether this, in combination with mostly sunny skies, will be enough to melt and dry roads. Much of the region north of Interstate 10 will remain below freezing during the daytime. Temperatures Tuesday night will only drop a little bit below freezing.

Wednesday and beyond

Part three of our collision with winter will come later in the week. Yet another storm system will approach from the west early on Wednesday, and it will draw Gulf moisture into the region. Much of the Houston metro area is likely to see another 0.5 to 1.0 inch of precipitation on Wednesday. This may start out as freezing rain early in the morning, but as daytime temperatures climb to about 40 degrees, it should turn to rain. This should also melt any lingering ice on roads.

However, temperatures on Wednesday night will probably drop below freezing for everywhere but the coast, so this sets up a situation where roads are problematic again on Wednesday night and Thursday morning due to ice. We’ll have to nail down these details in the coming days. Highs Thursday should rise above freezing and will hopefully melt any ice on the roads, but we’re going to remain close to freezing. Again, details to come on this.

Highs Friday should finally push at least into the mid-40s, with sunny skies. That will be the end of the winter storm. By Saturday, we should be into the 60s.

Final preparation tips

These suggestions were provided by Jeff Lindner, a meteorologist with the Harris County Flood Control District.

PIPES: Protect all and any exposed pipes, shut off and drain sprinkler systems. Open cabinet doors and closet doors to get as much heat against outside facing wall pipes as possible starting Sunday night. In some cases the best course of action may be to shut off water to a structure and drain pipes overnight when water usage is low to avoid pipes freezing and bursting.

PLANTS: Heavily cover and protect any tropical vegetation, citrus, or vulnerable plants. Given the intensity and depth of the freezing conditions this will likely be a killing freeze for much of the tropical landscape of this region.

PETS: Pets and livestock should have proper shelter, feed, and water. Normal water supplies will likely freeze over including stock ponds and lakes.

PEOPLE: Persons should plan to limit outdoor exposure Monday and Tuesday as wind chills will be dangerously cold for our region. Prolonged exposure could result in frostbite and hypothermia. Please ensure your neighbors have adequate heating.

Matt will have our next update on the site by around 4 or 5 pm CT today.

Good morning. Before jumping in to the forecast, I wanted to spend just a moment discussing why some areas of the region will see snow on Sunday night and Monday, and others sleet or freezing rain. It has to do with the temperature in the column of air above the surface, through which precipitation falls.

Snowflakes form high in the atmosphere, and if the temperature remains below 32 degrees as they fall thousands of feet to the surface, they remain snow. However, if there are pockets of warmer air and then sub-freezing temperatures again, sleet will form as snowflakes, melt, and then re-freeze as small ice pellets. And finally, if there is warmer air near the surface, but not at the surface, we’ll get freezing rain. The graphic below helps depict these processes.

This is the primary reason we think freezing rain is most likely near the coast—where the Arctic air mass will be most modified by the warmer Gulf of Mexico near the surface—and snow most likely over areas well inland. In terms of roads and potentially power lines, freezing rain is most problematic because it only takes a little to stick to roads and make them icy, and not that much more to accrue on power lines and weigh them down, or become more susceptible to blowing winds.

We’re starting to get closer to Monday, so higher resolution models are beginning to come into our forecasts, and as they do so confidence in which types of winter precipitation, and how much will fall, will increase.

Saturday

Temperatures are above freezing across the Houston area this morning, but only barely. They won’t rise a whole lot today, likely only reaching the upper 30s in Houston, and near 40 degrees along the coast. Buy hey, that’s better than freezing, right? In terms of wintry precipitation, our concerns now begin tonight for parts of the metro area northwest of a line from Katy to Tomball to Conroe. This is because lows for those areas are now expected to fall to about 30 degrees. This, in concert with light precipitation, could lead to some icing on elevated roads and bridges.

Sunday

Highs on Sunday should get into the mid-30s for even these inland areas, and warmer in Houston itself, so traveling across the metro area after mid-morning on Sunday should be fine. But the further west and north you go, you’re still going to run into freezing conditions.

Conditions begin to deteriorate by around sunset on Sunday in Houston. This is when we expect widespread precipitation to move into the area, and temperatures to begin to fall below 32 degrees. Some inland areas won’t see above freezing temperatures again until Wednesday.

Sunday night and Monday

This is when conditions on area roadways will become treacherous. As noted above, we expect snow to fall across inland areas where temperatures are the coldest, but we don’t know where snow will switch to sleet, only that this line will likely be somewhat north of Interstate 10. In terms of accumulations, here is our best forecast at this time, but it remains highly subject to change as additional high-resolution forecast models enter the picture.

Snowfall: For areas that receive it, about 1 inch, with 2 or more inches possible for Conroe and areas north of there.

Sleet: About 1 inch for central parts of the Houston metro area, with less north (where there will be more snow) and south (where freezing rain is more likely).

Freezing rain: About one-quarter inch for areas along and south of Interstate 10.

It now appears likely that precipitation will wrap up by around Noon on Monday, if not shortly before. Unfortunately, because temperatures at that time will probably only be in the low 20s for most of the area, whatever falls on the roads is not going anywhere. Moreover, with winds gusting out of the north above 30 mph, especially along the coast, it will feel like 10 degrees or below. Finally, these winds could play havoc with iced over power lines. So yeah, Monday is a day to stay home and hunker down.

Tuesday

After the precipitation ends, skies may begin to clear overnight. With extremely cold air in place, this will allow for ideal cooling conditions heading into Tuesday morning. And it will be exceptionally cold for Houston. Areas where there is snow on the ground, well west and north of Houston, may see temperatures of 5 to 10 degrees, and the coast will only be marginally warmer, in the low 20s. (The all-time record low for Houston is 5 degrees, set in 1930.)

Temperatures should reach above freezing, if barely, for areas south of Interstate 10 on Tuesday. But areas north of that line may continue to see freezing temperatures throughout Tuesday and Tuesday night. Lows will not fall much Tuesday night.

What this all means for roadways in the Houston for Tuesday morning and beyond is unclear. It will depend on how much precipitation falls Monday, in what form, and whether efforts to de-ice roadways are effective. I can offer no good predictions here, sorry.

Wednesday, Thursday, and Friday

Unfortunately, another round of precipitation is likely on Wednesday, as moisture moves inland from the Gulf of Mexico, and another front approaches. This will fall as rain on Wednesday, but for inland areas at least it could turn into sleet or freezing rain on Wednesday night—at least for areas along and north of Interstate 10.

The details of this are still very much in flux, but there’s a chance for more icy roads on Wednesday night and Thursday morning. At this time we do anticipate less impact than we’re likely to experience on Monday. Lows drop into the 20s on Thursday night, probably, before finally warming well above freezing on Friday.

And that’s the end. Saturday should get into the 50s or so, and by Sunday we’re back to highs in the 60s. Until then, it’s going to be absolutely frigid. Stay safe, y’all.

Matt will have a brief update on the forecast later today, and also take a first stab at historical significance of this kind of winter event for Houston.

 

 

 

Good evening. The overall forecast picture has not changed much today. We still expect a winter storm on Monday, with widespread problems on area roadways, followed by an extremely cold night and frigid Tuesday. Matt’s post from this morning still holds up well, but I just wanted to add a few more things that are becoming clearer as we get closer to the hard freeze.

There is still time to prepare

Conditions have fallen below freezing across much of the state, but most of the Houston metro area should remain above freezing until Sunday evening. That’s not to say it will be pleasant this weekend—highs are unlikely to rise above the low 40s, and there will be a chance of drizzle or light rain, especially Saturday night.

However, that means you still have the weekend to prepare for the winter storm, from wrapping your pipes or covering your garden for a hard freeze, to running to the grocery store. However, it now seems likely that by as early as Sunday evening light rain could turn to freezing precipitation. This means you should plan to be home, or wherever you’re going to hunker down, by around sunset on Sunday.

Monday looks pretty bad

Temperatures will fall below freezing Sunday night, and stay there for all of Monday, with the possible exception of Galveston and other beach locations. By tomorrow the higher resolution models should provide us more clarity on exactly what type of freezing precipitation will fall in Houston. But for the most part, we expect a mix of freezing rain and sleet in the city, with a greater likelihood of snow north of Houston.

Freezing rain would be the worst outcome, because as little as one-tenth of an inch will be enough to glaze over roadways. As more falls, it starts to accumulate on power lines, and that could eventually lead to power outages. Some recent models are leaning more toward sleet (ice pellets) than freezing rain, which would be good. We expect precipitation to end by early Monday afternoon, but with temperatures below freezing the ice isn’t going anywhere.

The bottom line: many if not all roads will be a mess either way, and you should stay home. If you’re an employer, you should at the very least tell employees to come in late on Monday, pending a final call. By early Monday morning we should have a better sense of just how bad things will get.

Models have trended slightly colder

If anything, the major models have trended slightly colder with lows on Monday night and into Tuesday morning. It now seems possible that areas of west Houston (i.e. Katy or Sugar Land) could see temperatures drop to around 10 degrees, with central Houston at about 15 degrees.

This is extraordinary cold. The all-time record low temperature for Houston is 5 degrees, set in 1930.

I would caution that there is still some wiggle room in the temperature forecast. There are a couple of factors that will ultimately determine lows on Tuesday: extent of snow cover, if any; whether clouds clear out before sunrise, and how calm winds become. But we are highly confident in a very hard freeze for the entire area.

When does this end?

Something else we’re trying to track is when this mess ends. It now seems pretty clear that any roads iced over will remain so through Tuesday night given the cold temperatures. The big question is whether temperatures will warm up enough on Tuesday to melt any icy or snowy roads.

There is not much agreement on this in the forecast models, but for now I think at the very least areas along Interstate 69, and closer to the coast, will warm to above freezing levels. I’m less certain about west and northwest parts of the metro area. Wednesday should bring above-freezing temperatures back to the area.

However, yet another front will bring more Arctic air into the region toward the end of the work week. We think there is a chance of yet another hard freeze on Thursday or Friday morning, and we can’t preclude more of a wintry mix on Wednesday or Thursday. We are reasonably confident that temperatures will recover by next weekend. So if you’re looking for an end to the winter madness, it’s likely coming about seven days from right now.

We’ll have a full update on the forecast on Saturday morning.

The Arctic front has pushed all the way off the coast and temperatures this morning are in the 30s and 40s. Welcome to your new reality, Houston. It’s possible the region won’t see temperatures in the 60s again for a week to 10 days, and there will be plenty of freezing weather in between. Our biggest concerns remain focused on next Monday—when roads could turn icy across much of the region—and Tuesday morning when lows could drop into the teens.

Thursday

Today will be rather grim, in terms of weather, with widespread showers and highs only reaching into the mid-40s. Most areas will likely see on the order of 0.5 to 1.0 inch of rain or so today and tonight, with higher amounts definitely possible underneath heavier showers. Lows tonight will get into the upper 30s, but stay above freezing and therefore keep roadways wet rather than slick in the metro area.

Friday

I think we’ll continue to see the potential for light rain on Friday, although the showers will not be as widespread as on Thursday. When it’s not raining, skies will be gray, and temperatures should again peak in the low 40s.

Saturday

The region should see a break in precipitation from Friday night into Saturday. Perhaps we’ll even get a peek at the Sun? Anyway, it won’t matter much as highs should remain confined to the mid- to upper 40s. Some slight rain chances may return later in the day or during the evening as an upper-level system approaches from the west. For now, low temperatures Saturday night will probably remain just above freezing in most of Houston, but inland areas may well see their first (of several) freezes during the coming stretch.

Sunday

Sunday will be another cold, gray day for the region. The models seem a little more bullish on some light rain falling, so lets call it 30 percent during the daytime. (It’s possible that some areas north of Conroe may see this falling as snow or freezing rain). Highs will be in the 40s, and as additional cold air starts moving into the region temperatures on Sunday night should drop into the 20s—mid- to upper-20s, maybe?—in the city of Houston, with colder conditions inland. The immediate coast may still avoid a freeze. We’ll see.

Monday

The outlook for Monday, which surely will change further so please bear that in mind, now looks to bring widespread, mostly light precipitation into the region from around sunrise to sunset. Because temperatures will be in the vicinity of freezing for much of the day, this raises the important question of whether this falls as cold rain, freezing rain, sleet, snow, or all of the above. At this point I’m reasonably confident that areas north of Interstate 10 will be cold enough on Monday, during the day time, to see some sort of wintry precipitation. I think the jury is still out on areas closer to the coast. But again, this day has the potential to be a real mess for traveling through the region, so be preparing for that possibility now.

Tuesday

We now think the precipitation will end sometime on Monday evening, or so, and this may allow for some clearing skies overnight and into Tuesday morning. (Will this allow roads to dry by Tuesday morning? It’s difficult to say). Regardless, the absence of insulating clouds will create ideal conditions for cooling with this very cold air mass. The region is virtually certain to see a hard freeze on Monday night and Tuesday morning, with lows potentially from 10 to 25 degrees in the city of Houston. This will wreak havoc with exposed exterior pipes and vegetation, and animals must not be left unprotected in these kinds of conditions. Check on neighbors to make sure their heat is working. Sunshine should allow temperatures to recover into the mid- to upper-30s on Tuesday. Lows Tuesday night will again flirt with freezing levels.

Wednesday and beyond

Forecast models indicate yet another reinforcing front moving into Houston on next Thursday or so that may again lead to a widespread freeze and raises the potential for some more wintry precipitation. I have zero confidence in trying to forecast that period. By next weekend we should finally be headed back toward days in the 60s and nights in the 40s, and this will all behind us. Spring, after all, isn’t too far away. But it’s not coming today!

Matt and I will, of course, be with you for the duration of this event.