How normal/abnormal was the winter of 2017-2018?
This winter’s precipitation had been in the normal range - until March.
Unlike regions of the country that have wet and dry seasons, eastern
Massachusetts averages approximately four inches of precipitation every month
of the year. As of March 4, i.e., between the first and second nor’easters,
precipitation had been one inch over average for the last 30 days and two
inches above the average for the last 12 months. [As of March 18, 2.3" higher than average for last 30 days and 3.7" higher for 12 months.] Of course, the Assabet River
fluctuates greatly in depth between winter and summer, but that is because in
the green months, plants are taking up huge quantities of water and releasing
that into the air, whereas in winter most it either sinks into the earth to
replenish our town’s water supply or else runs off to the river. The Assabet
has been well above average since New Year’s Day.
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| Creek near Assabet River, 1/1/18 Photo taken from footbridge |
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| Same creek, 48 hours later Click on photos to enlarge |
Temperatures were all over the place. From December 26 to the morning of January 11 the temperature never got above
freezing, and several nights got to -10F. Even the fast-running parts of the
Assabet River were nearly frozen over. Then, two days of temperatures in the
60s combined with steady rain almost completely obliterated the snow cover.
February temperatures were mostly in the normal range of below freezing at
night, warming to above freezing by day, but on February 20 and 21, spiked to
record setting highs above 70F. Whatever snow and ice cover that remained was
again wiped out. Tough year on local ski slope businesses. The first nor’easter
of March came in like a lion, the second one (March 7-8) was more of a snow leopard. The
wet snow of the latter broke branches on trees that had survived the high winds
of the former. And ANOTHER wet snow storm March 12-14! And 10F the morning of March 18!!.
Theoretically, there will be some benefits from those
ultra-cold January nights. Adult deer ticks can survive a moderately cold
winter, to plague us in early spring. But if the deep cold killed them all off,
then woods walkers have little to fear until the over wintering eggs hatch and tick
nymphs become active, in May. Likewise, the cold may have killed a majority of the
wooly adelgids that plague hemlock trees, providing a year’s respite (but no
permanent salvation from eventual tree death). For hemlock tree owners the only
options are insecticide spraying – or a chain saw.
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| Chart shows average monthly precipitation, in inches, using Boston data (raindrops and snowflakes). The swooping line is river volume. Figure created by Felice Katz for book: MAYNARD: History and Life Outdoors. |
Total snowfall had been a tad above average. Winters put about 45 inches
of snow on Boston and 65 inches of snow on Worcester. It’s a fare guess that
Stow and Maynard are in between. Counting the March 7-8 storm Boston’s winter
total was 41 inches. [The March 12-14 storm brought the Boston winter total to 57.2 inches]. The last two big years for Boston were 2010-11 with 81
inches and 2014-15 with a record-setting 110 inches of snow. Between the two,
2011-12 was a low snow year, at 9.3 inches.
The long-term trend is that winters have been getting
shorter, but snowier. Of the ten snowiest winters since record-keeping began in
1890, six have been in the last twenty-five years. The reason is that eastern
Massachusetts has been getting wetter (up 10 percent) faster than warmer (up
one degree F). But at some point in the future that upward snow trend will
collapse, because once nor’easters are above freezing temperatures those storms
will be heavy rain events rather than snow events. Portland, Maine has already
experienced a crossover. Weather records dating back to 1870 show a bit warmer,
much wetter, less snow.
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| March 8, 2018 "Nice hat" |
Of course, winter is not over until it’s over. April 1, 1997
was the infamous April Fool’s nor’easter that put two feet of snow on Boston
and nearly three feet on Worcester. Two days earlier had been sunny and in the
60’s, so people were unprepared for the idea of a pending storm. The storm
started as rain, but as evening fell the air temperature dropped a couple of
degrees more than expected and snow was suddenly coming down at 2-3 inches per
hour. Across mid-Atlantic and New England states, more than one million people
lost power. Twenty years earlier there was a snowstorm on May 9, 1977. Not as
widespread as 1997 (Boston got less than an inch), but suburbs west and
northwest of Route 128 got more than a foot of wet snow. Because trees had
already leafed out, the damage was tremendous.
Observe that we are looking at
pretty much twenty year intervals. So maybe these March storms were pre-ordained.
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