That 4-letter word ... snow

You can kiss the mild weather good-bye for a while, as a real outbreak of winter is taking shape over the Carolinas and much of the eastern United States.

Among the highlights (or lowlights, if you're not a winter weather fan):

1. A chance of snow mixing with rain for a few hours after midnight Saturday in the Charlotte area.

2. Very cold temperatures next week in the region, with daytime highs struggling to get out of the low 40s some days.

3. The lurking possibility of a winter storm sometime around Dec. 13.

The weather pattern in the Northern Hemisphere is undergoing a major shift, because strong high pressure has established itself over Greenland. That is blocking the typical west-to-east movement of weather systems, and instead, we're getting exaggerated dips in the jet stream.

One of those dips is over the eastern United States. Another is over the British Isles. Heavy snow has been falling the past few days over parts of England and Scotland, with up to 10 inches accumulating in some London suburbs. It's unheard-of weather for this time of year in that part of the world.

Closer to home, the cold weather we've experienced the past 24 hours is merely a tuneup for what's ahead.

It dropped to 23 degrees Thursday morning at Charlotte/Douglas International Airport, the coldest since a 22-degree reading March 7. But it could fall to near 20 degrees next week.

A low pressure system will dive southward Saturday, crossing North Carolina and bringing rain and snow showers. Meteorologists -- the National Weather Service, The Weather Channel and Accu-Weather -- agree that the precipitation will fall as rain over South Carolina and snow in the N.C. mountains.

It looks like rain showers will move into the Charlotte area Saturday evening, and they could mix with snow for a few hours early Sunday. Some forecasters think places like Winston-Salem, Greensboro and Raleigh could get a coating of snow from this system.

If you're going to the ACC championship football game Saturday evening, look for cloudy skies, temperatures in the low 40s, and a small chance of a rain shower.

The weekend low will usher in the really cold air. A northwest flow will establish itself, and while that type of pattern produces dry weather in the Charlotte region, it will be very, very chilly.

You can expect daytime highs in the low 40s and morning lows in the lower 20s for the first three or four days next week -- and that's despite full sunshine during the daytime hours.

The computer models continue to indicate the chance of a big winter storm around Dec. 13 (a week from Monday). I mentioned this earlier in the week, and the long-range forecasts continue to show such a system developing. The computer models haven't changed much for a couple days, putting Charlotte in an area that could get cold rain or frozen precipitation.

By the way ... the other computer model-predicted wintry storm was supposed to have developed Dec. 8. That's Wednesday, and it looks as if we'll have absolutely dry conditions, although it will be plenty cold enough for snow.

I mention that busted Dec. 8 forecast to remind all of us that Dec. 13 could wind up being dry, too.

Bastardi's White Christmas. I know some of you weather geeks are not big fans of Accu-Weather's Joe Bastardi, who specializes in long-range forecasts. But it's interesting to note that Bastardi is predicting that about half the country will have a white Christmas. That compares, he says, to an average of 25 to 30 percent of the United States having snow on Dec. 25.

His map of snow on Christmas includes parts of North Carolina, with the line drawn quite close to the Interstate 85 corridor.

I'll go with the averages. Snowfall is recorded in Charlotte, on average, about once every 25 or 30 years.