Though we will look back at the 2020 season for too many of
the wrong reasons, it still had its moments. It won’t rank as one of the better
winters over the past 25 years and most certainly resides in the bottom half of
that sample size. With that said, it is probably closer to the middle than the
bottom and at least northern Vermont could brag about some some while other
locations to the south saw hardly any.
The above graph is from the ever-popular Mt Mansfield snow
stake site. I actually prefer to take a sampling of final snowfall totals from
various ski areas around the northeast (sometimes outside of the northeast) but
most stopped reporting as of mid-March. “The Stake” at Mt Mansfield apparently
can’t be stopped and it always proves to be an invaluable resource for weather
and data enthusiasts such as myself. The color coded lines can appear a bit
blurry to the eyes but the pink line is 2020 and it runs behind most years this
past decade with the exception of the of 2011-2012 and the Super-Nino
debauchery of 2015-2016. We were able to keep pace with 2017-2018 for a while
but were unable to score another miracle March and instead recorded a rather
ordinary to sub-ordinary one. The 5-week "arctic spring" is also notable. More on that below.
Choosing the one single variable that defined the personality of the past winter was easy this year. Hands down it was the Arctic Oscillation (AO). Scientists have officially been tracking that index going back to 1950 and it remains one of the best gauges we have to measure how blocked the jet stream is over high latitude regions of the Northern Hemisphere. When aggregating over a 5-month period (Nov-Mar) the AO this past winter was the 2nd highest ever recorded. 1989-1990 remains the winner and 1990-1991 had a strong bronze medal showing but 2019-20 both intense and persistent, often challenging the confines of the graphical display while spending all but a few weeks in positive territory. Below is a chart measuring the top 5 +AO years and top 5 -AO years
When you consider those headwinds, 2019-2020 doesn’t look
quite as bad. 1989-90 and 1990-91 were decidedly worse snow years based on data
from the Mt Mansfield snow stake and 1992-1993 benefitted from of the greatest
winter storms of all time. It also shows that Vermont can survive the adverse
impacts of a +AO year a lot better than areas farther south. Winter across the
Mid-Atlantic was nearly non-existent and ski areas suffered a much milder fate
relative to Vermont. Atlanta, GA was nearly 4 degrees above normal over that
same 5-month period. 4 degrees may not be a lot for one month but over the
course of 5 months makes it one of the warmest winters on record. The same can
be said with -AO winters. All 5 winters on the above chart were good snow years
but the record year 2009-2010 actually featured a weather pattern that became
too “blocked” and many of the best storms missed Vermont and deposited snow on
the I95 corridor instead. Atlanta, GA by the way, recorded one of the coldest
winters over this same period. 1968-69 was absolutely historic in Vermont and
one of the best snow years ever recorded in many locations.
We also spent much of the winter talking about the
persistent tightness of the jet stream in the mid-latitude Pacific Ocean. This
zonal, fast to east moving consolidated jet stream mitigates the impacts of
arctic air over mid-latitude North America and the index that best measures
this is the Eastern Pacific Oscillation (EPO) index. The positive index which
is defined by a version of this weather map is largely what we saw throughout
the winter. Notice the cold over Alaska which was very prevalent through much
of the past several months.
Though the EPO was very positive through much of the winter,
once I went through the rather tedious process of parsing through all the daily
data I found that the positive value of around +33 was closer to zero than I
would have thought. The two winters prior to this recorded values in the mean
of close to -60 and the super evil empire winter of 2011-2012 recorded a value
of close to +80. In other words, the EPO was an issue but the +AO, based on the
aggregated data, was a bigger issue.
If I had to identify a single culprit to the persistence of
the +AO/Somewhat +EPO pattern this winter it would be the configuration of sea
surface temperatures in the Pacific. More specifically, the massive blob of sea
surface temperature warmth that positioned itself south of the Gulf of Alaska. It
was a large contributor to what became a negative Pacific Decadal Oscillation
season. A negative PDO is not, in and of itself a pattern killer for snow and
winter lovers in New England but the persistence of a jet stream level ridge
underneath a glaring lack of blocking in the Arctic became the most prevalent
adverse variable in almost every update I did this past season. Interestingly,
this feature was identified in the
pre-season outlook as a concern but it was pitted against what was, at
the time, a glaring lack of sea ice in the Chukchi Sea (regional body of water
north of the Bering Strait). As it turned out, the Chukchi Sea quickly froze
and we were left with the anomalous body of sea surface temperature warmth
described above. Such a sea surface temperature setup is often associated with
La Nina winters but not this time. The equatorial Pacific stayed on the Nino
side of zero throughout the winter, and though we did see an energized southern
branch of the jet stream at times, the weak El Nino did not greatly influence
our winter season one way or another.
November and early December saw the best stretch of pattern
fundamentals and the season was off to a promising start. The high country
surrounding the MRV did see several small but measurable rounds of accumulating
snow and temperatures were 5-7 below normal for November which was colder than
2018. The biggest difference however was the lack of Snowvember. We were teased
with the idea of big storms on a few occasions but nothing ever materialized.
Thanksgiving was white but just not “deep” white. Still, the persistent cold
was promising and it finally looked like the pattern would bear fruit in early
December thanks to a bombing area of low pressure along the east coast. Though
the storm did deliver several inches to the MRV, the heaviest snow fell across
southern Vermont, the Berkshires, Albany, NY and the Catskill Mountains to the
southwest. I feel like this storm was an inflection point. Had we bullseyed
that sucker, and we were close, we may have remembered this winter very
differently.
Cold weather persisted in a general sense to about the
winter solstice but there were two somewhat damaging thaws within the week of
December 9th to 15th that limited our ability to
establish a base. The coldest day of the season was actually December 19th
when the high temperature struggled to reach 5 but we only managed to muster a
few inches of snowsqualls and had limited snowcover going into the holiday. At
that point, the pattern broke down and much of what was described in the above
paragraphs, a very positive AO (unblocked Arctic), a somewhat positive EPO
(zonal Pacific Jet) became the prevailing influence on our weather pattern.
Christmas was wintry but there were several days around Christmas that were
not.
The loss of Rush drummer Neil Peart cast a dark shadow on
the early part of January 2020 for me personally. Looking back, I suppose it
was a lead indicator of the rough year that was to come. On the weather side of things, the 10 days
that began on around December 29 and ended around January 8th was
one of the better stretches of the season. Though the pattern wasn’t entirely
supportive, a once upper Midwest blizzard deposited a mixture of snow and sleet
on the MRV and provided a few days of instability leading up to New Years Day.
No it wasn’t epic, but we got a bit of all of the necessary ingredients
starting with a good base building storm a few a few inches of powder on the 30th,
the 31st and on New Years Day. Temperatures crept above the freezing
mark for a few days on the January 2nd, and 3rd but we
were able to score some additional snowfall on the 4th and procured
a nice first weekend of the new decade. A few days of snow showers and squalls
during the following week gave us a temporary impression that winter was
resettling in. Unfortunately, this didn’t last. A very mild weekend January 11th
and 12th and some rain put a massive dent into the base and put a
crimp into the rest of the month. We got a bit of cold weather and snow in the
week that followed but the big storm proved to be elusive. The best chance for
one came without much cold air support on the last full weekend of the month. I
remember talking about walking the proverbial “tightrope” and hoping for the
perfect storm track. In the end we kinda fell off the tightrope a bit but did
receive a bit of decent snow across the high country while the low elevations
got a bit of wet weather.
February was a tale of the “same story, better result”. It
was historically awful for snow along the I95 corridor including all of
southern New England and New York City. Boston recorded only a half inch of
snow for the entire month and New York City only recorded a trace. As the AO
continued to soar, nearly breaching the limits of the visual chart on two
occasions, temperatures continued to run above average across much of the
United States including Vermont which saw readings 3-5 above average. We did
get the snow however, mainly from two different but substantial events. The first
on February 6-7 was the best of the season. It was a windy event which proved
to be a challenge for some resorts to manage but we got the powder, almost 2
feet of it and we got a few days of cold weather on the ensuing weekend which
included a calm Sunday February 9th. The other big event occurred toward
the end of the month. It was a wetter snow event at the low elevations but an
overperformer nonetheless with around a foot of snow. We had hoped to score the
additional instability snow leading into the weekend but winds remained
westerly as opposed to northwesterly favoring the snow over locations such as
Stowe and points north. The two storms in February might have made the month a
more memorable one but there was a lot of mild weather in the middle of the
month. We did manage to avoid much of the rain but not all of it.
March brought in the Covid19 pandemic so I suppose it was good
year to not have our traditional mid-month snow bonanza. The first 15 days made
up the last 15 days of the season for most resorts and it featured big
temperature surges and occasional rainfall. It didn’t look especially good for
a wintry finish to the season but it goes to show that you just never know. I am
saying this completely in jest but it is almost as if the pattern waited or Governor
Phil Scott to issue his stay at home order and suddenly everything fell into line.
The positive AO became completely neutralized and a “well blocked” jet stream
emerged. It showed up in the NAO data the best but we also saw blocking over the
Yukon which fueled an amazing and persistent stretch of winter-like weather
over Vermont in the middle of spring.
Much of Vermont did see a nice overperforming wet snow of
nearly a foot in some places on March 23rd, but the true “arctic
spring” didn’t commence until around April 9th. It was 5 weeks of remarkable
spring cold and some substantial snow. So much snow in fact that Mt Mansfield
had a 2nd peak of snow pack in early May. More on that later. The 5
weeks beginning on April 9th and ending around May 13th
was roughly 7 degrees below average and much of the high country didn’t see any
60-degree temperatures throughout April. We did see several rounds of snow,
some elevation sensitive, some not so much. Though we never did see the epic
April powder producer (that would come in May), I would estimate that Mad River
and Sugarbush saw at least 20 inches of snow in April. It got even more
incredible in early May. Following a spring-tease May 1-3, a massive surge of
May cold descended on New England. A storm on May 8th and 9th
produced 5-10 inches of not wet snow but powder across much of the northern
Vermont high country. I will remember May 9th for as long as I can remember
the dates of all my favorite weather events. Sub-zero wind chills, temperatures
in the 30’s all day, snow squalls and several inches of snow on the ground
throughout the day. It was truly surreal! Then, in a total about face, a heat
wave hit Vermont in a span of less than 3 weeks. Most official reporting sites
in Vermont hit 90 degrees oddly beating locations such as Philadelphia and Washington,
DC that have yet to see 90 degrees this spring (a rarity)
In many ways 2020 has not been a year we would ever hope
for. It certainly was not a memorable winter season from a weather standpoint either
but will obviously be remembered for worse reasons years from now. The 5-weeks
of winter that the Vermont high country saw in spring has brought some optimism
and provided a reminder of what CAN BE. I can hope, like the rest of us, that
we can come to a resolution as to an appropriate way to face the challenges on the
ground and have a ski season we can all enjoy. Look forward to being back next
winter to serve the MRV like always. Until then, stay engaged and continue to
work the make our community a special one and the world a better place both now
and in the future.