Temperatures are going to plummet before Christmas. The question is how low they will go

The month of December has started off ridiculously warm. Through Monday the region has recorded an average temperature of 69 degrees, which is 12 degrees above normal. However, after one more day the greater Houston region will see a shift toward more winter-like weather. It is not going to get spectacularly cold, rather temperatures will just slip back toward our typical December pattern of highs generally in the 60s, with lows in the 40s. The real question is what comes after that. Looking at the big picture, we can see that the coldest air mass on the planet, at present, lies over the Siberia region of Russia, where surface temperatures in some locations are in the -55 to -75 degree Fahrenheit range.

The pattern over the next week suggests that this very cold air will be drawn into Canada. After that, it’s a matter of where this air mass goes. A preponderance of modeling brings it down into the Central United States. And then? Well the question is whether the air continues diving into the deep South, toward the Gulf of Mexico, or is shunted more eastward. At this point we are talking about weather 8 to 10 days from now, so uncertainty in this is high. However, there is clearly the potential for very cold air to move into Texas, whereby we could see lows in the teens over the Christmas holiday in Houston. Low temperatures might also be 40 degrees. This far out it is difficult to forecast with any real confidence. But it is going to get cold during the last week of this year. Perhaps even very cold to the point where we need to worry about pipes, pets, plants, and power. We should have more confidence in this forecast in a couple of days.

Tuesday

In contrast to what is coming later this month, Tuesday will be absolutely balmy. Low temperatures this morning have only fallen to around 70 degrees in Houston. We’re going to see spotty showers this morning, with perhaps some thunderstorms developing this afternoon or early evening ahead of a cold front. While we cannot rule out some severe storms, at this time I expect most of this weather to remain northeast of the Houston metro area. Look for highs today to push near 80 degrees, with high humidity. Winds will be gusty, out of the south, at up to 20 mph before the front. Drier air should move in with the front this evening, perhaps reaching the metro area around 6 to 9 pm, and the coast by around midnight.

Wednesday

Lows on Wednesday morning may briefly dip into the 50s, but with clearing skies we should see highs climb into the low 60s. As moderate northerly winds back off on Wednesday night we’ll see low temperatures drop efficiently, down into the mid-40s in Houston, with colder conditions for outlying areas.

Thursday and Friday

These will be a pair of winter-like days, with sunny skies and highs in the vicinity of the low 60s. Overnight lows will be in the 40s. This period represents our best chance of guaranteed sunshine for awhile, so soak it up.

Saturday and Sunday

An additional shot of cooler air arrives on Friday night, and this will lead to chilly conditions this weekend with highs in the 50s, or possibly 60 degrees by Sunday. Both days will be partly sunny, but also have a decent chance of rain. The challenging part of the forecast is that we’re pretty confident there will be some showers offshore, but we’re not certain whether and how far this rainfall will migrate inland. So if you live south of Interstate 10, call it a 30 or 40 percent chance of light rain each day, with lesser chances further inland.

Monday

An onshore flow looks set to resume on Sunday, and this will probably set the stage for a wetter Monday ahead of the region’s next cold front. How wet? I would not be surprised to see 1 to 2 inches of rainfall on a warmer day when highs climb into the 60s, because there will be plenty of atmospheric moisture to work with.

Tuesday and beyond

We’ve got a cold front penciled in for Tuesday of next week, which may drop lows into the 30s for a few days. After that the most plausible scenario is a shot of even colder Arctic air, as discussed at the outset of this post. It becomes really difficult to parse details beyond this, but the overall pattern does support the influx of much colder air just prior to, and on Christmas Day. I think the atmosphere probably will be too dry to squeeze out any snowfall, but at this point I would not entirely rule out a white Christmas in Houston. I just would not put the chances at much higher than 10 percent.

Even though the holidays are coming, rest assured that Matt, Maria, and I will be covering this all for you as much as needed.