I'm Dreaming of a Dry Christmas

Most people in South Carolina usually dream of a white Christmas.  There have been so few times that it has happened in this area.  In fact Climate Central did the calculations and the chances are less that 1% of seeing a white Christmas in Columbia.  Where is the best place to be?  See the map below:

The chance of seeing a white Christmas across the U.S.  Click on the image for a larger version.  Image Credit: Climate Central.

Even though the map shows the historical odds of a white Christmas, the actual amount of snow in a given location can vary a lot from year to year due to natural weather variations.  For example, this year, U.S. snow cover in mid-December was the largest it’s been in a decade.  Outside the U.S., it’s worth noting that Siberia, generally one of the coldest places on Earth for this time of year, had a scorching November with temperatures up to 14°F higher than normal.  That warm trend has continued into December, leaving a "snow shortage".  We can identify with a snow shortage.

Weather's Ups & Downs

It has been like a roller coaster for temperatures since late October beginning with a freeze on the 26^th Columbia, SC, when the temperature dropped to 30°F.  This came after an exceptionally warm fall.  Here is a look at the ups and downs since October 26^th:

Month	Date	Temp
Oct	26	30°
	30	82°
Nov	4	38°
	6	77°
	9	32°
	10	72°
	14	23°	New Record Low
	18	85°	New Record High; Trace of Snow Evening
	19	38°
	22	76°
	25	22°
	26	71°
	28	23°
Dec	6	82°	Record High Tied
	13	25°
	21	81°	New Record High

The forecast for the 22^nd of December is for record high temperatures with much colder weather returning for Christmas Day.  Thus the roller coaster will continue for a while.

What is causing this?