Arctic cold front arrives Thursday night

HOUSTON - We're about to get a harsh reminder that we're in the dead of winter and this time we may have a little wintry precipitation to marvel at, especially north of Houston.

Now granted any wintry precipitation, whether it be a single sleet pellet or a single flurry is a big deal in these parts but even this ''event'' will pale in comparison to the snow and ice events of yesteryear. So sorry to disappoint but that's the best we can do at this point. More on that in a moment.

First, let's talk cold.

Cold Temperatures:

This arctic blast is as strong as any we've seen this season. It will push through Houston on Thursday night bringing with it the possibility of sub-freezing temperatures all the way into Houston by Saturday and Sunday mornings and again on Monday, especially for areas north of Houston.

Once temperatures fall into the 40s on Thursday night they will remain there until at least Monday. That means Friday, Saturday and Sunday will remain in the 40s all day long. 

Temperatures are expected to remain above freezing on Thursday night/ Friday morning thanks to a thick blanket of clouds that will hover over southeast Texas in association with a coastal low that is expected to develop. Look for overnight lows Thursday to only make it down to the mid 40s--but will continue to fall throughout the day on Friday. By Friday night, the low is expected to depart the area allowing for clearing skies into Saturday morning and remaining clear well into Monday.

Those clear skies will set the stage for efficient cooling of the surface and temperatures will respond by dropping into the upper 20s and low 30s Saturday morning and even colder by Sunday morning with many areas north of I-10 falling into the mid and upper 20s.

This will not be a pipe bursting freeze for the city. However, tender plants and animals will need shelter.

What's this about wintry precip?

Unlike the last big cold blast we experienced where the front blew through and pushed all the moisture out of the area, this time a coastal low is expected to form behind the arctic front: the perfect recipe for snow and ice over southeast Texas.

Unfortunately, the low is expected to form very close to Houston therefore keeping the warmer air nearby. However Chief Meteorologist David Paul says, ''it's a fine line. You want the low near by but not this close. On the other hand if the low is too far away, it robs us of the moisture. Therefore it gets colder but there's no moisture to work with.'' 

Areas as far south as College Station, Huntsville and Livingston may very well see rain mixed with sleet but the precipitation is expected to be light. Therefore with surface temperatures above freezing, travel impacts are not anticipated anywhere close to the Houston area. This will have to be monitored closely because the models have been and continue to trend colder with the airmass. This could lead credence to sleet or freezing rain occurring a bit further south than currently forecast.

As far as any snow goes, expect the flakes to fly around the Dallas and Shreveport areas to as far south as perhaps Lufkin. 

So why will it snow in Dallas and not Houston? Check this out. We monitor something called the "Skew T." It's a 3D slice of the atmosphere that shows us what the temperatures are doing above our heads.

The picture above is the Skew T near Houston. The yellow line represents the freezing point. Notice how the red and green lines are to the right of the yellow line. That means the rain is falling through an atmosphere that is above freezing therefore unable to make a snowflake. However you'll notice near the bottom of the image, in the blue circle, which represents the surface where we live, there is a brief moment where the rain falls through air below freezing (it crosses the yellow line). Therefore it's not impossible to see some sleet pellets mixed in with the rain close to Houston Friday night.

The picture above is from the Dallas area. Notice how the red and green lines are left of the yellow line. This means that the atmosphere is cold enough and deep enough to allow snowflakes to form and make it to the ground. 

What you need to do:

If you live anywhere in the viewing area, except maybe the immediate coast, it's that time again  to bring in the plants. Again, this will not be a pipe bursting hard freeze for Houston. Therefore practice safety with space heaters, protect tropical plants and give the animals a warm place to nest for the night, during the too for that matter.

Exercise caution if your travels take you north to Austin, Dallas or Shreveport where snow and ice may coat some of the elevated roadways. At this time widespread travel impacts are not expected but we'll continue to keep you updated as necessary. 

 

(© 2017 KHOU)


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