Another Chinook

South winds aloft pushed very warm warm air into the central Interior Alaska Friday night and Saturday morning, resulting in dawn temperatures more typical of July than the autumnal equinox. In the Fairbanks area at 8am ADT, temperatures were mostly in the 50s and lower 60s. Here is the 500 mb analysis for 4am ADT Saturday. Note the strong ridge extending from western Montana northward to west of the Mackenzie River, with deep southerly flow over nearly all of mainland Alaska.

Courtesy of Environment Canada

The warming on the Fairbanks sounding between Friday afternoon and Saturday morning was quite dramatic (lowest 1500 meters plotted below). In most places the overnight low temperatures occurred Friday evening and then rose steadily after midnight. Here on Keystone Ridge the high temperature Friday of 55F occurred shortly before midnight. At the Goldstream Creek PWS, the temperature fell to 36F by 1030pm but jumped from 43F to 57F between 5am and 6am as the wind broke through the inversion.

The cirrus is fairly thick this morning but will likely thin in the afternoon, and it is possible, albeit unlikely that the record high for September 22nd of 73F set in 1995 would be broken.