Still Cold in Kotz

The temperature contrast between western and eastern Alaska can be pretty striking at this time of year, as the interior warms up quickly, but the Bering Sea coast can still be locked in with wintry conditions.  Today is a case in point: Eagle has reached at least 67°F, but it's a breezy, sub-freezing day along parts of the west coast.

Looking more closely at Kotzebue in the northwest, it has been distinctly cold this week, with the morning temperature dropping to 8-10°F on Monday, Tuesday, and Wednesday.  It's been 10 years (2013) since this kind of cold was observed so late in the season, and prior to 2013 we have to go back to 1966 to see colder conditions.  Kotz has yet to see its first daily-mean temperature above freezing this year, and even in earlier decades of the 20th century that would have been unusual at this point on the calendar.

Yesterday afternoon's 500mb map shows the immediate reason for the big west-east contrast: a trough over Alaska's west coast, and a big ridge over western Canada.  The red circle indicates Kotzebue's location:

This pattern is typical for the time of year, as abundant Bering Sea ice produces a major chilling effect compared to the land area to the east.  But this goes beyond the simple matter of the ice acting as a refrigerator.  With snow mostly gone from the continental interior, a tremendous amount of solar energy is absorbed, leading to rapid warming, but the sun is much less effective at warming the reflective snow and ice of the Bering Sea.  And to add insult to injury for the west coast, there's a lot less sunshine to begin with because of that semi-permanent upper-level trough, so cold begets cold in the west.

On another note, here's just one more piece of evidence to show how remarkably cold it was for northwestern Alaska in the first half of April: daily maximum and minimum charts for the CRN site near Selawik.

In the second week of the month, this site saw 6 of 7 days with a low temperature below -30°F, and the temperature didn't rise above 0°F for 8 days straight.  Considering Fairbanks has never seen an April day with a high below 0°F, and Bettles has only seen a handful, this was a remarkable cold spell.