Turning Wintry

Snow has been on the ground in Fairbanks since late last week, and at this point it is unlikely to melt out, despite a warm forecast for Halloween.  (Temperatures are expected to get above freezing in the next couple of days, which is unusual for the time of year, but not extreme - it was 48°F on Halloween 4 years ago.)

Other than the great chinook and "brown Christmas" events of 1934, the latest date in the year with at least two inches of snow on the ground that subsequently melted out in Fairbanks was October 26 in 1940.  So if two inches of snow is observed at the end of October, it's almost certainly safe to remain there until spring.

Here's the history of snowpack onset date in Fairbanks; this year's presumed date of October 24 is not unusual.  1934 and 1992 were the two big outliers.

Temperatures have been dropping off statewide since I posted about "lack of cold" on the 18th, driven by rather strong troughing from the Bering Sea to the Gulf of Alaska:

Interestingly, Utqiaġvik yesterday dropped to -10°F, and the daily average temperature was below 0°F for the first time in October since 2018, and before that since 2002.  Until the mid-1990s, a daily mean temperature below 0°F in October wasn't at all unusual, occurring in more years than not, but this is only the fifth such day since 1996.

Looking back at autumn in Utqiaġvik, it's interesting to observe how little unusual warmth there has been in comparison to the past decade.  It looks like the October and September-October averages will be the coolest since 2015, but of course that's still well above the normal of the 20th century.

Warm Weather Follow-Up

Following up on snow conditions in southwestern Alaska, there hasn't been any clear weather lately to reassess snow cover from satellite, but FAA webcam images now show very little snow for most or all low-elevation locations in the southwestern mainland to the south of the Yukon River.

Sparse or no snow extends at least as far north as Holy Cross and Crooked Creek; but Sleetmute still has snow cover, as does (much farther inland) McGrath:

The warmth in Bethel has been quite pervasive since early December, and the average temperature since December 1 is the sixth highest on record; 1979 holds the record.  2018 (second place) was quite a bit warmer than this winter so far.

The Kuskokwim 300 race has been postponed because of the poor trail conditions:

https://www.kyuk.org/kuskokwim-300/2025-01-17/postponed-kuskokwim-300-receives-support-from-mushers-vets-and-volunteers

However, the latest CPC forecast does suggest a change is on the way:

Also noteworthy is extreme warmth on the North Slope this week; early Sunday saw 41°F at Umiat, which ties the record for January.  Temperatures above +40°F were observed from Cape Lisburne in the far west to the easternmost extent of the North Slope - click to enlarge:

Where is all the cold air?  Down south is where: New Orleans had a foot of snow today.

September Climate Anomalies

First, to follow up on the last post - the answer is no, the snow didn't survive in Fairbanks - at least not at the official snow monitoring site, which I believe is now at the university farm (location of the longest-running continuous climate record in Alaska).

Several days with daytime temperatures in the low 40s, and a lot of rain, doomed the early attempt at establishing snow cover.  The first 10 days of the month have now seen 1.28" of liquid-equivalent precipitation in Fairbanks, which is the 4th highest on record; and the top two spots are held by 2017 and 2019, so this is the 3rd time in 5 years with a very wet start to the month.

Looking back at September, here are the temperature and precipitation rank maps from NOAA/NCEI's climate division data: most of the state was in the lower tercile of the 1991-2020 distribution, and areas from Bristol Bay to south-central were much colder than normal.

Here's Rick Thoman's usual graphic showing the absolute temperature anomalies: note the remarkable -5.5°F anomaly at King Salmon.

And here's the ERA5 view of the month: it was yet another cloudy month in the northwest, but unlike during summer the winds were relatively light across western Alaska.

As an aside, I previously noted that the NCEI data seemed much too cold for the North Slope in July, but the value has been adjusted since then, and the latest result for July is much more reasonable - see below.  So it seems we should treat NCEI's preliminary monthly numbers with some caution.

Will The Snow Survive?

The heavy, wet snow that fell at the weekend left several inches on the ground in the Fairbanks area, which of course is unusual for the time of year.   Fewer than 1 in 5 years have snow on the ground at valley level in the first few days of October, although it doesn't take much of a memory to recall the remarkable late September snowfall in 2015.  Back then over 13" of snow fell, which is more in line with what happened this time at locations to the southeast of Fairbanks.

It's interesting to ask whether this very early snow cover will last through the winter.  In 2015 it didn't: it was all gone by the middle of October.  It's tough to keep a relatively shallow early snow cover, as the temperature in Fairbanks reaches at least 45°F after October 5 in most years, and 50°F or higher is not at all uncommon.  In fact, if this year's snow does last, it will be the second earliest onset of the winter snow pack on record (1930-present); 1992 holds the record of September 13, but that was a very extreme outlier.

If we look at years that had at least 3" of snow on the ground by October 5, we find that it disappeared 8 out of 13 times.  For 4" or 5" on the ground this early, the survival rate is about 50%, although the sample size is small.  However, if we look at years with at least 3" on the ground between October 6 and 10, the odds of it surviving are much higher: about 80%.

So from a statistical perspective it looks like there's now a decent chance the snow will last, but it's obviously highly contingent on the weather.  Above-normal temperatures of any magnitude will probably doom the early snow cover, and rain - which is in the forecast for the next couple of days - may also prove fatal.

Here's the afternoon river view at Nenana, with the relatively unusual situation of having ice (snow) on the ground but not on the river.  Most of the year has ice cover on both or neither, and typically April - and sometimes much of May - has ice only on the river.

North Slope Meltout

Spring has arrived in earnest on the North Slope in the past week, and the NWS noted today that breakup is underway:

209 PM AKDT WED MAY 27 2020

...BREAK-UP UNDER WAY ACROSS THE NORTH SLOPE...

WARM TEMPERATURES IN THE BROOKS RANGE ARE CAUSING RAPID SNOW MELT
THAT WILL CONTINUE THROUGH THIS WEEKEND. RIVERS DRAINING TO THE NORTH
SUCH AS THE COLVILLE, KUPARUK AND SAGAVANIRKTOK RIVERS ALL HAVE 
ICE REMAINING NEAR THE COAST, AND COULD HAVE ICE JAM ISSUES THIS 
WEEK AND WEEKEND AS RISING WATER LEVELS MOVE DOWNSTREAM. 

RIVERS NEAR THE ARCTIC COAST SHOULD BE MONITORED CLOSELY FOR ICE 
JAMS AND POTENTIAL FLOODING THROUGH THIS WEEKEND.

Here's the latest NWS breakup map (click to enlarge).

The average date for breakup at the Colville River delta is June 3, based on reports since 1996, so this year will not be far from normal.  The historical chart - see below - suggests a trend towards later breakup, but this is entirely because of two early years at the beginning of the series.  The long-term trend in temperature during May is most decidedly up.

Here are a couple of satellite images that illustrate the extent of snow cover remaining; the first image below is from Monday afternoon, and the second image is from today (click to enlarge).  Patchy cloud cover obscures the situation slightly, but there's no doubt the snow is disappearing.

[Update Friday pm: here's a great view from today, courtesy of and annotated by Rick Thoman.]

The Umiat webcams confirm that snow is gone on the middle Colville River (289' elevation), and even up at Toolik Lake (2460') there's a lot of bare ground now.  Both of these sites have exceeded 60°F already; summer's here.

Snow Cover

Fairbanks saw an inch or two of fresh snow last night and this morning, and most of interior Alaska now has at least a light covering.  The last area to hold out is the low-elevation northwestern interior and parts of the Seward Peninsula, which remain snow-free as of this afternoon.  Here's a satellite photo from 2pm, with the Seward Peninsula at left and the now-icy Yukon River clearly visible.  (As an aside, it's interesting to note several "streaks" of snow cover coming off Kotzebue Sound; I assume these were caused by episodes of heavy snow showers, or clusters of showers, that formed over the (very) warm water.  It looks like much of the western and northern Seward Peninsula also got its snow cover in the same way.)

With a storm system approaching from the southwest (see the thick high clouds at lower left), this may be the last time we see this area without its winter mantle of white.

According to snow cover data at the Rutgers Snow Lab, the normal date for onset of snow cover in the northwest interior is about October 10-12, based on satellite data from 1970-2000; so we're about two weeks late this year.  Here are images showing the daily normal on October 6, 13, and 20.

Comparing today's analysis with last year's for the same date, there is actually considerably more snow cover across both Alaska and western Canada this year; despite very warm waters across the northern Pacific Ocean, the weather pattern has favored relatively chilly conditions over northwestern North America (except at Arctic latitudes) in recent weeks.  However, this is set to change in a big way for Alaska, as the aforementioned storm system over the Aleutians is building a very strong ridge downstream that will bring exceptional warmth to Alaska for at least the next week.  Sadly I wouldn't be surprised if it's even warm enough to wipe out the early snow cover in many areas; we shall see.

Snow Cover in the Interior

Rick T. here with with a (mostly) clear sky from Monday afternoon October 14, 2019, showing a fairly well defined line between areas to the south and east of Fairbanks that picked up quite a bit snow during the second week of October and areas to the west, where low elevations are still snow-free. Urban Fairbanks is right on the edge. The snowfall from Delta  Junction southeastward was quite impressive. 15" of snow at Tok was the greatest October snowstorm (over two days) there on record (climate obs since the late 1950s) and second greatest overall. Delta Junction does not often get a foot of snow in one pop, but they did from this event, including severe drifting. 

Snow Arrives

As befits the date on the calendar, snow cover has started expanding across Alaska, with many northern and/or elevated locations now seeing a light covering.  This afternoon's land cover classification image from the Suomi polar orbiter is obscured by cloud cover across much of western Alaska and parts of the North Slope, but nevertheless the image clearly shows some snow on the ground in much of the north (except the Yukon Flats) as well as the Yukon-Tanana uplands.

FAA webcams revealed a pretty scene in Bettles this morning, where the temperature dropped to a chilly but not unusual +7°F.

Up in the northeast at Arctic Village, things are starting to look wintry as well, with a covering of ice on the ponds.

But perhaps surprisingly, Toolik Lake (on the north side of the Brooks Range) is not yet frozen over despite some rather chilly weather in the last couple of weeks.

Moving farther north still, Teshekpuk Lake shows no sign of any ice yet, and the same appears to be true of the smaller lake that's visible on the webcam at Inigok:

And finally, today's climate report from Utqiaġvik stated that there was zero snow on the ground, although the webcam view from earlier today suggests this may not be accurate (or is no longer true):

A couple of weeks ago I mentioned that the first measurable snow of the season has never occurred in Fairbanks earlier than in Utqiaġvik, but this year there has at least been a tie, and Fairbanks may in fact have been earlier (the daily snow numbers are missing from Utqiaġvik for Oct 5th and 6th).

The absence of snow in the north until now is not because it's been dry; Utqiaġvik had nearly an inch of precipitation in the second half of September, but it nearly all fell as rain (there was just a trace of snow).  The average temperature for September was easily the highest on record, exceeding 40°F for the first time on record, and every single day had a daily mean temperature above freezing (also for the first time).  Previously the latest arrival of a sub-freezing daily mean temperature was September 30, 1998, but Utqiaġvik has yet to see such a day this autumn.  And so the warmth in Alaska's far north continues to break records as the trend of recent years persists apparently unabated.

Meltout in Fairbanks

Snow depth dropped to only a trace in Fairbanks on Thursday, according to the daily NWS climate report, meaning that April 4th marked this year's meltout of the seasonal snowpack.  Somewhat surprisingly this is not the earliest on record; that distinction belongs to 1970, which saw meltout one day earlier, although snow returned that very same day in 1970 and then remained for another 10 days.  The earliest for a permanent meltout (no subsequent observations of an inch or more of snow depth) was just 3 years ago: April 9, 2016.

Here's a chart of Fairbanks meltout date since 1930.  As noted on previous occasions, there is no long-term trend, and it's possible that this has to do with greater late winter snow depths in recent decades - see here for my comments from 2016.