People who aren't involved in the weather on a daily basis can easily forget past trends. Almost every January has produced a warm spell, and almost every February has produced snow or cold. How easily we forget!
It's true that the first 13 days of January saw temperatures average 10-14 degrees below average. If that were to continue we would see the coldest January on record, fortunately that's not going to happen.
We have to look to El Nino for clues as to why the warm up. The waters in the Pacific continue to warm. As El Nino strengthens, a ridge of high pressure expands into the western U.S. This pushes the polar jet stream back to the north taking the cold air with it. It also allows the sub-tropical jet stream to become more active across the southern U.S. This is what has happened during the second half of January 2010.
Three of the past four El Nino winters saw temperatures fall to below average during February or March. Remember, February of 2009 saw 10 inches of snow in NE Arkansas and in March of 2008, Little Rock saw snow. Winter, is NOT over.