Cooling Off

Late September is late autumn in interior Alaska, and after an unusually warm first half of the month, the calendar is now exerting its influence.  Some accumulating snow occurred yesterday in the higher hills around Fairbanks, and the international airport finally observed its first freeze of the season this morning.  Only 5 years in Fairbanks history have waited longer for the first freeze, with the record being September 27 (1974).

Snow is sticking on the trees on Ester Dome near Fairbanks. This image was taken at 2066 feet or 630 meters in elevation. Picture taken today by a NWS employee on 9/21/2019 #Snow #Fairbanks #akwx pic.twitter.com/MS85v8cygy

— NWS Fairbanks (@NWSFairbanks) September 22, 2019

Of course the usual cold spots have been seeing freezes for weeks (see the chart below for 2m temperatures from Smith Lake on the UAF campus).  Smith Lake dropped to 22°F last night, and so did Tanana on the middle Yukon River as well as Shungnak in the northwestern interior.  Tanana had a freeze more than a month ago, on August 19.

What about snowfall?  Fairbanks often doesn't see its first accumulating snow at valley-level until early or even mid-October, but late September is more common in the northern interior.  Bettles already saw a notable 3.4" of snow a few days ago, and this provides an interesting contrast to the mild and snowless conditions on the other side of the Brooks Range (i.e. the North Slope).  Utqiaġvik (formerly Barrow) has not seen accumulating snow yet, and interestingly there has only been one other year - 2007 - when Bettles beat Utqiaġvik to first measurable snow, and that was only by 3 days.  Fairbanks has never (in the modern climate record) seen measurable snow before Utqiaġvik, but it might not be impossible this year.

Below are charts of the date of first measurable snow for Fairbanks, Bettles, Utqiaġvik, and a couple more sites for good measure.

(Note to regular readers: I'll be traveling for the next couple of weeks, so probably won't be posting anything in that time.)