Monday, April 22, 2024

Warming Up Fast

A very strong upper-level ridge over Southeast Alaska and northwestern Canada has produced a big warm-up for eastern and southern Alaska in the last week, with temperatures reaching record levels for the time of year in some spots.  Yakutat reached 64°F on Friday, which would be the warmest on record this early in the season if it were not for a similar warm-up in 2021.  Numerous locations set daily record highs on Friday and/or Saturday, from Ketchikan (65°F) in the far south to Bettles in the northern interior (56°F).

Here's the 500mb analysis from 4pm AKDT on Thursday, courtesy of Environment Canada:

The most unusual warmth I spotted was at Cordova, where the daily minimum temperature of 47°F on Thursday was the highest overnight minimum this early in the season by a full 3 weeks.  Bettles also saw a record warm night for this early, with a low temperature of 39°F on Thursday despite having 29" of snow on the ground at that time.

As of the last daily report, Fairbanks snow depth is down to 3", so the official meltout date may well be today.  The ice at Nenana is looking very rotten, and the accumulation of thawing heat units is now in the historical range for breakup.  However, with unusually thick ice this year - measured at 50" a couple of weeks ago - perhaps it will be a few more days before the tripod goes out.

With meltout occurring earlier this year than the last two seasons (both in early May), green-up and fire season in the eastern interior will probably come to life a bit earlier as well.  Here's an article discussing this, with a few comments from Rick Thoman:

It makes sense that there would be a connection between early snowpack loss and increased early-season fire activity, so I had a quick look to see if this shows up in the data.  The chart below shows June 1 fire acreage statewide versus the snowpack meltout date in Fairbanks:

There does seem to be something of a relationship, although it's marginal and the sample size is small (I only have daily fire data back to 1995).  If we step forward to July 1, the relationship seems to disappear:

The highest July 1 acreage on the chart was in 2022, when the Yukon-Kuskokwim region saw unprecedented early fire activity owing to a very dry spring; there's a lot more to the puzzle than just the timing of meltout.

1 comment:

  1. The semi-Alaskan Bird (mosquito) appeared today in Fairbanks. Still some snow on north facing roofs and in the hills tho. The Birch trees are dripping water from their buds, and the Cottonwood tree's buds are getting sappy. "Spring has sprung, the bugs have riz, we wonder where the flowers is?"