Return of the Inversion

I was outside at 1230am Sunday and the sky was filled with stars; just a band band of light on the northern horizon (one of the many benefits of outdoor plumbing). Weather-wise, this can only mean one thing: the return of the inversion.
On the left is the temperature plot from the 3AM upper air sounding from Fairbanks, showing a 6.4ºC temperature increase in the lowest 300 meters. The spread in morning low temperatures is of course wider. Lows include: 26ºF at the Salcha River RAWS, 29ºF at the Angel Creek RAWS. 30ºF at Goldstream Creek Co-op, 32F at the Woodsmoke (near North Pole) PWS, up to lows of 50ºF at Clearly Summit and the Nenana Hills RWISs and 48ºF here on Keystone Ridge, making it one of the mildest overnight lows of the month.