Cooling off

This morning's POES IR imagery (610AM ADT) shows a fair amount of clear skies over Interior Alaska, and with the rapidly lengthening nights, this can only mean one thing…down go the temperatures.

Subfreezing minimums are now routine in the cold valley bottom locations: 28F this morning at Goldstream Creek, and 22F at the Beaver Creek RAWS on the Yukon Flats. Even the "routine" valley places are getting colder: 31F at Eielson AFB, 35F at UAF West Ridge, and even Fairbanks International dipped to 38F, the first sub-40F temperature this autumn. It's pure radiative cooling: 850 mb temp +5.0C this morning on the Fairbanks RAOB and higher elevation min temps were well up in the 40s: 45F here at Keystone Ridge and 48F at Clearly Summit.