Saturday, November 18, 2017

Winter's Chill

[Update Sunday 6pm]

Last night was colder, especially in the Fortymile Country, with -35 to -38°F in several locations and a rather remarkable -43°F at Chicken.  Far to the north, satellite estimates suggest it may have been below -45°F in Arctic Village and its environs, but unfortunately the Arctic Village AWOS has not been reporting lately.

[End of Update]

Distinctly chilly conditions have descended upon Fairbanks and indeed most of the eastern interior, with widespread -20s and some -30s Fahrenheit this morning.  Here are some of the coldest spots, with higher-elevation valley sites and the Fortymile Country being well represented:

-38°F  Atigun River HADS site at 2600', near Galbraith Lake (north of Atigun Pass)
-35°F  Chicken co-op site (1800')
-31°F  Fortymile River at the Taylor Highway (HADS site at 2100')
-30°F  Salcha RAWS (900')
-30°F  Wade Creek at the Taylor Highway (HADS site at 1965')
-29°F  Tok 70SE CRN site (2000')

In Fairbanks the international airport reached -23°F, the Goldstream Creek co-op saw -22°F, and Eielson AFB reached -20°F, but North Pole only hit -18°F.  It's quite unusual for the airport to be the coldest spot in the area.  Tonight looks to be colder as the 5-minute observations from Fairbanks airport showed a 10°F temperature drop right after sunset just a short while ago - see below (sunset was at 15:34 AKST today):

This morning's -35°F at Chicken is right on schedule, as the 1997-2016 median date for first -35°F reading is tomorrow, November 19.  In Fairbanks it is "normal" to see the first -20°F or colder on November 17, so again this cold spell is right on time.

Here's the 500mb map (courtesy of Environment Canada) from 3am this morning.  Cold air is being imported from the north in the strong pressure gradient between the Pacific/Bering Sea ridge and the cold low over Canada's Melville Island.  The cold low is really cold - notice the -40s Celsius temperatures around it.  As for the Bering Sea ridge, this has been a persistent feature of the pattern in recent weeks and is a clear expression of a La Niña influence.  I'll have more to say about this in a subsequent post.

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