January Climate Data

Looking back at Alaska climate data for January, the month was a story of two dramatically different halves, with the prolonged mid-winter cold snap ending (on a statewide basis) right at the month's midpoint.  It's worth recalling again just how persistent the cold was for that period of six weeks ending January 15; here's the UAF statewide temperature index since November 1st:

The contrast in the mid-atmosphere pressure pattern could hardly be greater between the first and second halves of the month.  The first half of January saw a strong trough planted right over the state, but this reversed to a high pressure ridge for the second half:

Owing to the dramatic turn-around, the monthly average temperature wasn't all that unusual, only 3.5°F below normal, and even the coldest climate division (Bristol Bay) was considerably warmer than January 2020 (and even more so than January 2012).  Southeast Alaska was warmer than normal, as unusual cold only lasted through the first few days of the month there.

Amazingly, the December 31st record 50-inch snowpack in Juneau melted out completely by the middle of January, with 30 inches disappearing in a rainy second week of the month.  All of Southeast Alaska and the eastern half of the state at large was considerably wetter than normal, while the west coast and western interior were dry, along with most of the Alaska Peninsula.

The dryness across the Seward Peninsula and interior northwest compounded a lack of snow from earlier in the winter (see figures below), and snowpack was far below normal by February 1 for places like Nome, Kotzebue, and Ambler - at least according to ERA5 data.

The ERA5 temperature map above shows that unusual cold was widespread over the eastern half of the Bering Sea, and so it's no surprise that sea ice expanded more quickly than normal, nearly reaching St Paul Island by the end of the month.

Sea ice did in fact reach St Paul Island a few days later, according to the NWS analysis:

Nevertheless, on a monthly basis, January Bering Sea ice extent was about 12% below the 1991-2020 normal, because of deficits in the western half of the basin.  The basin-wide total was in line with the past several years, and seems to have stabilized (for now) well above the 2015-2018 lows.