The persistent absence of cold conditions aloft has been a very prominent feature of the winter in Fairbanks so far, and in fact it's record-breaking by quite a large margin. The chart below shows the lowest observed value of the column maximum temperature in the early winter, i.e. prior to the turn of the year, for each year since 1948. Remarkably, this winter's balloon soundings from Fairbanks have not yet observed a column colder than -11.1 °C (+12 °F) throughout the troposphere; there has always been air at least this warm at some level. The previous record in this respect was -18.5 °C (-1 °F) in 1953. The chart shows an interesting pattern of rising minima in recent decades, indicating that this year's outcome is a continuation of a long-term trend.
Another way of expressing the extreme persistence of warmth this winter is that only two soundings so far have observed a column colder than -10 °C throughout (back in November). The next closest winter in this regard is 2000-2001, with 13 soundings colder than -10 °C by the turn of the year, and even the exceptionally warm early winter of 2002 had 22 soundings meeting this threshold of cold.