Wednesday, February 24, 2021

Late Winter Chill

It's getting rather late in the winter for harsh cold in much of Alaska (excepting perhaps the North Slope where it's more typical), but that didn't stop the thermometer from dropping to -42°F at Fairbanks airport on Monday morning.  This is the coldest of the winter so far, and the first -40° of the season in the Golden Heart City.  It's also the first time since 2007 that such cold has occurred so late in the winter.

In keeping with my last post, temperatures aloft were significantly below normal on Monday morning above Fairbanks: about -20°C at 850mb and -38°C at 500mb.  Cold air was circulating around a very intense mid-atmosphere low pressure system just to the west of Canada's Arctic Archipelago - see below.  This is a remarkable turnaround from the record high pressure that occurred in the same area just two weeks ago.


Here's the Fairbanks sounding from 3am AKST on Monday.  Even though winds were out of the west (and even slightly south of west in the lower troposphere), the airmass had an Arctic rather than southerly origin.

Checking in on that notorious cold spot, Chicken, they also saw -40° in the last few days.  No surprise there, but what is surprising is that Chicken has produced more -40° readings this month than in any other February: 14 of them so far (although with an 8am obs time, it's not actually 14 different nights).  Warmer air has arrived now, and the next few days will remain warmer, but there's still a chance it may be the coldest February on record for Chicken (but with data only back to 1997).  However, for the winter as a whole, the temperature is running near normal, with the -40° count approaching a typical two dozen.

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