Spring Contrasts

Clear skies and calm winds produced a widespread freeze across eastern and northern Alaska this morning, with the temperature dropping into the 20s in most locations.  Fairbanks airport reached 29°F, which is a little unusual in the modern climate for this late in the season; other than last year, it hasn't happened after May 10 since 2013.  The low temperature in Chicken was 19°F, which is the first time below 20°F this late in the season since 2014.

Farther north, accumulating snow fell in Fort Yukon yesterday morning.  The accumulation was probably less than an inch, given that the snowfall rate was light, but temperatures were below freezing, and it was falling for over three hours.  Snowfall measurements haven't been available from Fort Yukon for many years, but historical data shows an inch of snow as late as mid-June in 1971, and as early as late August in 1961.  It's a short summer in the northern interior.

Farther north still, the North Slope is still locked in with wintry weather.  The high temperature in Utqiaġvik yesterday was only 13°F, and that's a little more notable: we have to go back to 2007 to find a colder day this late in the season.  Utqiaġvik temperatures have been oscillating between above and below the 1991-2020 normal so far this year:

The contrast between North Slope winter and interior spring made me wonder when the seasonal contrast between the two regions is greatest.  It is indeed in spring: the following chart shows the difference between normal temperatures in Utqiaġvik versus the average of Bettles, McGrath, and Fairbanks.

The Arctic coast doesn't begin climbing out of winter cold until nearly April, but the interior has gained a lot of warmth by then, and the temperature contrast peaks in late April.  Of course, the interior cools off much more quickly in autumn, and the valley-level interior becomes briefly colder than Utqiaġvik in November.

Looking back at April, it was a cloudy and wet month for most areas except the North Slope and Southeast.  With precipitation well below normal in the usually wet Southeast, the state-average precipitation was not much above normal, but the southwest and southern interior were unusually damp for the time of year.

The broad swath of wet weather was caused by strong westerly flow to the north of a robust Gulf of Alaska ridge, and downstream of the ridge the dry anomaly was inevitable over Southeast Alaska.

Statewide mean temperatures in April were very close to the modern normal, with equally balanced ups and downs during the month.  The Aleutians were significantly warmer than normal, although not to the extent of some recent years (2016, 2020).

Cloud cover was well above normal for most of the state.  The combination of cloudy and damp weather certainly wasn't a bad thing in terms of wildfire risk as we advance quickly toward fire season.