As Rick alluded to in his post yesterday, this is the time of year when temperature inversions usually become more persistent and dominant in the Fairbanks area. In fact, today is the day when the climatological daily mean temperature becomes lower at Fairbanks airport than on Keystone Ridge (the latter being over 1100 feet higher); this will remain true until mid-April.
The chart below shows the annual variation in normal daily maximum and minimum temperatures at the two locations, based on the 1981-2010 climate normals. On average, temperature inversion occurs at the time of daily minimum temperature for nearly nine months of the year, while inversions tend to persist throughout the day for the four deep winter months of November through February. In January the tendency for inversion is so strong that Fairbanks average high temperatures are close to Keystone Ridge average low temperatures.