Kevin Myatt is The Roanoke Times' weather columnist.

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The astronomical calendar labels the winter solstice -- about Dec. 21 -- as the beginning of winter. The meteorological calendar labels Dec. 1 as the beginning of winter.

But the weather pattern has declared a different beginning date of winter this time around: Jan. 16.

For two months, an amazingly stable weather pattern has kept mild air from the Pacific Ocean flowing over North America, with only two brief interruptions. But some gears in that machine have broken, and cold air from Canada and the Arctic Circle has at last flooded the United States.

The result of this abrupt midwinter changing of seasons has been a massive winter storm that has killed more than 40 people while coating locations from south Texas to northern Maine in ice and snow. As with all previous intrusions of cold, the core of the harshest conditions has settled into the central part of the country rather than into the East.

But this time around, a measure of cold has moved into the East as well, enough to take us back down from the 50s and 60s to more typical January temperatures: 40s in the day, 20s at night.

There is no real sign this new weather pattern will change much in the foreseeable future. You can't rule out a day or two of milder weather between cold fronts on occasion for the rest of this month, but prolonged unseasonable warmth appears to be shelved for at least the next two to four weeks.

Don't be surprised to see some more extreme cold eventually, but for now, seasonable January cold appears to be on the menu.

The atmospheric pattern over the Pacific is propelling this chilly turn, and there appear to be at least a few more shots of Arctic air on the way.

If the atmospheric pattern over the Atlantic comes into line, this could become a prolonged and memorable period of wintry weather for us, the alter ego to the springlike warmth we've been experiencing. There are mixed signals about whether that will happen.

The main question on most people's minds now is when we will see our first widespread winter storm in Southwest Virginia. We've had a couple of light snows that have dusted the typical higher elevation areas and places west of Interstate 81, but nothing that has really brought the Gulf of Mexico moisture together with Arctic cold to give all of the area some wintry precipitation.

There are two shots at it this week, neither of which looks to be a slam dunk, but which bear watching.

The first is on Thursday, as the system causing snow and ice around Austin and San Antonio, Texas, on Tuesday slips east and then north up the coast.

Southwest Virginia could be on the western edge of the precipitation, which would give the area maybe a one in three chance of some significant snow or ice. The Piedmont will be even more in line for wintry precipitation than will places from the Blue Ridge westward.

But if the system nudges a little farther west, that could change. A nudge eastward, and it's a clean miss. Just follow the forecasts.

Anything that falls will probably be light.

A larger, wetter storm is likely to affect the area late in the weekend. The questions surrounding it are whether the cold air will hold deep enough for its arrival.

It will be cold, but are we talking below-freezing cold for snow or ice, or just chilly rain cold in the mid-30s to low 40s?

If temperatures are low enough, it could become the region's first large winter storm of the season. At this point, my best guess would be some snow changing to ice and then to rain. We have a few days to watch it.

Whether these snow/ice opportunities come to fruition or not, there will be no doubt that conditions typical of January are back.

You didn't really think winter was going to hibernate all winter, did you?