Early Snowpack

The onset of winter sometimes seems to occur almost instantaneously in Alaska.  The sudden change of season happens most obviously when temperatures drop more rapidly than usual around the climatological transition into the long freeze of winter, leading to a nearly binary switch from above-freezing to persistently below-freezing.  This year is an example: here's a chart of daily mean temperatures in Fairbanks since August 1.  The arrival of cold with the first snow on October 3 marked the sudden change.

Assuming the five inches of snow now on the ground in Fairbanks doesn't melt out, October 6 this year will mark the earliest onset of the sustained winter snowpack since 2014, and within the top 10 earliest since 1930.  Read some comments from 2014 here:

https://ak-wx.blogspot.com/2014/10/early-snowpack.html

There's no significant trend in snowpack onset dates for Fairbanks, and interestingly the 10 earliest dates have occurred at quite regular intervals over the decades.  The latest onset dates show more clustering: a few in the 1930s, and another group in recent years.

Looking farther north in the interior, Bettles also shows no trend (with data since 1951).  The roughly 180 miles makes a difference of about 9 days in the median date (October 10 in Bettles, October 19 in Fairbanks).

However, it is interesting to see that Bettles has not seen a September onset for 15 years now, whereas it occurred 8 times between 1950 and 2010.  Only once (1992) has Fairbanks seen a September snowpack start.  Conversely, Bettles hasn't seen bare ground at the end of October since 1974, whereas it's not too unusual in Fairbanks (and seemed to become commonplace in the last decade or so).

In other interior weather news, Tanana reached a chilly 0°F yesterday morning.  This is the earliest 0°F reading in Tanana since 1996, and it's good for 10th earliest (tied) in the history since 1901 (with some missing data).

Overall the state is seeing the coldest start to October since 2014, judging from the ACCAP standardized statewide index.  Except for 2021, every year from 2015-2022 was quite a bit warmer than normal for the first two weeks of October, so it's a refreshing change.

Cold West, Warm East

The recent weather pattern, with a persistent trough over far eastern Russia and the Bering Sea, has allowed winter to make an appearance over western Alaska, while central and eastern areas have been much warmer.  The contrast reached an extreme last weekend, as deep southerly flow and a major chinook brought excessive warmth to the eastern interior.

Remarkably, it has been almost two weeks since Fairbanks had a daily mean temperature lower than Nome, and this is very unusual indeed for the time of year.  Typically the interior cools off much more quickly in late autumn than the west coast, owing to the strong maritime influence in the west and the lack of ice in the Bering Sea.  Because of this, early November is the time of year when Nome is most likely to be warmer than Fairbanks, i.e. the opposite of what's happening this year.

In the first half of November, Nome is warmer than Fairbanks on 87% of all days, according to the 1930-2020 history, and in recent years this percentage has risen still higher, as the Bering Sea has been so warm.  For instance, in the past decade only 12 days between Nov 1 and Nov 15 have been as cold or colder in Nome than Fairbanks, i.e. 8% of all days in that window; and yet we are currently standing at 12 such days in a row.  Here's a chart of daily mean temperatures, and their 1981-2010 normals, in the two locations since September 1.

The freeze-up situation reflects the unusual contrast: there has been lots of ice on the Yukon out west for days now, but the Tanana River still shows mostly open water.  Here's a webcam photo of the Yukon at Grayling from more than a week ago, versus the Nenana webcam today:

The notorious cold spot of Chicken has only dropped to -4°F so far this season, a far cry from last year, when -40° was reached more than once in early November.  Looking at a map of the lowest temperatures since October 1 (click to enlarge images below) shows many locations yet to see 0°F or even single digits Fahrenheit from Nenana to Fairbanks and in the Yukon-Tanana uplands.

Here are a few 500mb maps to illustrate the circulation pattern, including the remarkable chinook last weekend.  Note the persistent trough over far eastern Russia: an anchor point for the cold air mass that has been entrenched over western Alaska.

3am AKST Oct 26:

3am AKST Oct 31:

3am AKST Nov 5: