North Slope Chill

The first half of March was the coldest since 2012 for the North Slope, providing a notable contrast to the last decade - although it wasn't significantly colder than the long-term mean for the second half of the 20th century.  Utqiaġvik had a mean temperature of -21°F, and Deadhorse came in at -29°F.  Unfortunately the Umiat RAWS hasn't been reporting all winter, but the nearby HADS site reported an average temperature of -32°F for March 1-15, and that's close to the -33°F reported by the RAWS instrument in 2012.

Here's the last month of temperatures from the Umiat HADS site (in Fahrenheit):

The -52°F on March 11 seems pretty cold for the time of year, but it's not especially unusual in the context of earlier years.  The RAWS site saw -52°F a week later in 2008 (March 19), and much colder episodes occurred at the pre-RAWS climate observing site (1976-2001, and also 1945-1954).  Back in 2001, -63°F was observed on March 13, and perhaps the most astonishing of all is -50°F on April 5, 1986 - and that's the all-time state record low for April.

The number of -40° nights at Umiat in March has dropped off sharply since 2012:

As for Deadhorse, the 7 nights with -40° so far this month is a bit more unusual, as not many years have exceeded that number in the combined history from Prudhoe Bay (admittedly slightly warmer) and Deadhorse.

The cause of the cold is an unusually strong trough over the Beaufort Sea and extending down across Alaska.  The following maps show the estimated departure from normal of the 500mb height (top) and 850mb temperature (bottom) for the first half of the month: