Good evening. The last round of sleet and snow is marching through the Houston area, and by around 8pm the precipitation should be done for Houston today. For the next 24 hours there are three issues I want to discuss—icy roads this evening, frigid temperatures tonight, and when roads will clear on Wednesday.

Icy roads Tuesday night

Road conditions continue to worsen across the metro area this evening, and with sub-freezing temperatures and the loss of sunlight, there will be no real opportunity for concrete and asphalt to dry out. Already, Houston Transtar has reported 100 locations on major area roadways with ice, and that tally should continue to rise. Please do not venture out this evening or tonight, if at all possible. Sure, there is a chance you will make it to your destination without a problem. But there also is a chance you will not, and then place yourself, your passengers, and first responders in additional danger.

Overnight lows

Houston faces a very, very cold night. Clouds this evening should help trap some of the heat, but some models predict that skies will begin to clear after midnight, and the earlier this occurs tonight, the better the chance for temperatures to really bottom out. The forecast shown below, from the National Weather Service, reflects what I think is a realistic worst-case scenario for lows tonight.

You may have some concerns about pipes, given the cold temperatures. This site provides some good, general advice for a freeze like Houston will experience tonight. By the way, the record low for Jan. 17 in Houston is 15 degrees, set in 1930.

Wednesday’s roads

School districts faced a difficult call in regard to Wednesday. On one hand, it is going to be decidedly frigid on Wednesday morning, and some roads will certainly be icy in the Houston metro area. On the other hand, at some point Wednesday the ice is going to melt and it will be business as usual for Houston. Moreover, kids in most districts have already missed at least 12 days due to weather-related closures. In the end, almost every school district opted for the safe choice, and closed their doors.

Frankly, I’m not sure what conditions we’re going to see Wednesday morning. I think a fair number of roadways will be passable, but at the same time untreated bridges and overpasses will be deceptively dangerous. The big question for me is how much of the metro area’s elevated roadways will be treated with a solution to effectively melt the ice? I don’t know.

What I am confident in is that, sometime between 10am and noon on Wednesday, as the Sun comes out, and temperatures rise to above freezing, Houston’s roads will melt and dry pretty quickly—for good. By this weekend we should see highs rebound to the 60s, and we should remain there for most of the rest of the month.

As temperatures have plunged across the Houston area during the last six hours, rain has turned into a wintry mix of sleet, freezing rain, and snow. (Yes, it has already snowed lightly at Bush Intercontinental Airport this morning, the first time that has happened three times in a winter season since 1973). Here’s a look at what happens next.

More precipitation is coming

Houston has seen some breaks in the rain and sleet this morning, but there are additional areas of precipitation to the west of the region that will move into the metro area today. Although accumulations are unlikely to be too significant, it doesn’t take much moisture on the surface of a road to make it slick. Forecast models have been pretty consistent in bringing additional rounds of sleet, freezing rain, and snow through the region until about 4pm to 6pm CT today. Snow is more likely than other precipitation types this afternoon.

Roads are starting to freeze

Houston Transtar is keeping a (steadily growing) list of roadways affected by ice in the metro area. So far, most of the problems have occurred to the north, in Montgomery County, and west of Houston. This is understandable, as those areas have experienced freezing conditions for a longer period of time. Most roadways within Houston itself are still covered with just water, because the ground is still “warm” from Monday, when highs reached into the upper 60s. But now that most of Houston is now at about 30 degrees, and likely to slip into the upper 20s this afternoon, wet roads will gradually become icy roads—especially bridges and overpasses. How much of an ice rink Houston becomes depends upon the amount of precipitation this afternoon. With enough wind and breaks in the precipitation, there is a chance for some evaporation and perhaps we will have dry roads by the time the hard freeze hits tonight. Perhaps. But probably not. Best to leave work early today, if possible, and stay home this evening.

See full post

As expected, a very strong cold front has moved through Houston this morning, and we’re in for a potentially messy day as precipitation falls on and off the day until about sunset. As of 5:45am CT we are already seeing a wintry mix over northwestern Harris County and Montgomery County. More freezing rain and sleet will move into the area later this morning as the freezing line moves from north of Houston, through the city, and down to Galveston by around noon.

Essentially, as the air cools down, the region is likely to see a progression from rain, to freezing rain, to sleet, to snow. This is largely driven by the depth of the warm air, which will decrease throughout the day as cold air moves into the region from the north. Here’s a graphic showing under which conditions each type of wintry precipitation falls.

Our concern for today in Houston, and the reason why schools and some businesses closed, is because of the transition from rain to freezing rain, which has the potential to very quickly ice over roads. Now, let’s take a detailed look at what may transpire later today.

See full post

Schools are closing for Tuesday, and given what we know about the forecast, that seems a sensible precaution. Already, the National Weather Service has issued a winter storm warning for the entire metro area along and north of Interstate 10, and this effectively means there is a significant potential for snow and ice accumulation.

Basically, a mess is coming. The cold front arriving between midnight and sunrise on Tuesday seems to be a little bit colder than advertised, and this means that a freezing line should move through Houston earlier than expected, perhaps within an hour or two of sunrise. And that means the potential for freezing rain—the worst of all kinds of winter precipitation because it makes roadways incredibly slippery even with slight accumulations—will move into Houston around the same time.

Road crews are treating freeways and other major arteries with a salt-based solution that lowers the freezing temperature of water and could help some, but under the present forecast we can still expect some bridges and overpasses to freeze, in addition to untreated roads. In short, if you don’t have to get up and drive to work on Tuesday morning, don’t. If you run a business, please consider giving your employees the day off. It is by no means certain that some or many Houston roadways will be icy Tuesday morning or midday, but at this point there’s a pretty good chance.

The precipitation, some of which may transition from freezing rain to sleet or snow later on Tuesday across Houston, should end by the afternoon or evening hours. But with temperatures remaining below freezing, and depending on how much rain falls, roads may not improve much after the precipitation stops during the evening and overnight hours.

We will have a comprehensive update by 6am CT on Tuesday.