Welcome to winter! Major below-normal cold swing begins this week

But whatever the calendar may say, temperatures are on their way down and likely won’t rise much, if any, through at least mid-December. The average high temperature in early December is in the lower 40s, and we will likely drop to at least 10 degrees below normal by this weekend as a piece of the polar vortex drops southward into the Hudson Bay area of Canada.

READ MORE: After a busy November, what can we expect from December weather?

At the same time, a large area of high pressure will build across the North Atlantic near Greenland. This blocking area of high pressure will force cold air that is building from the North Pole into northern Canada and southward across the eastern half of the United States.

The block can cause the polar vortex to weaken and even splinter into “spokes” that can get pushed southward toward the U.S.-Canadian border. Such patterns lead to some of the coldest temperatures of the year in Ohio, especially in the months of January and February. While the air that is now moving into the Miami Valley will be quite cold, it will not be as extreme as it could be if the same pattern were to occur again in about four to six weeks.

If the long-range models are correct, the pattern now developing will likely hold through mid-December. This will keep temperatures well below average with occasional bouts of snow showers and/or flurries. Such patterns often don’t lead to major precipitation events, although clipper-type systems are common. These “Alberta Clippers” will bring gusty winds, rapid temperature swings and a couple of inches of snow at most. Such a system may be on track to move into the Ohio Valley this weekend with perhaps another one passing early next week.

The bigger question will be if such a pattern will hold into the holiday week of Christmas, which is still just too far away to know for sure. While chances appear to be better than average (typically about 30 percent) for a white Christmas, there are some signs that the blocking pattern may begin to break down right around that time.

Eric Elwell is WHIO StormCenter 7 Chief Meteorologist. Contact him at eric.elwell@coxinc.com or follow him on Facebook and Twitter.