Snow By Marc B. Fried The Mohonk Preserve has recently completed its 110th unbroken year of weather observations, and a recent article by the Preserve's Shanan Smiley includes a bar graph showing snowfall amounts for each winter season. Cutting from left to right across the bar graph is an evenly ascending line telling us that something called the "linear average" of seasonal snowfall at Mohonk has increased significantly from approximately 50 inches to 70 inches during this 110-year period, even as the annual temperature has risen by a scary 2.3° F. Snowfall amounts in the neighboring valleys would obviously be less than the Mohonk figures, while snowfall on the loftiest parts of the ridge (overlooking Napanoch and Ellenville), fully 1000 feet higher than the Mohonk station, would be greater.

Linear average? I asked the author of the article how this is arrived at, since it's apparent from the graph that it is not simply a calculation of mean or median. She acknowledged that this was a computer-driven calculation and that she was frankly in the dark as to how a linear average is arrived at. Three math professors I queried had never heard of the term, and on-line inquiries were not helpful. It is apparent, though, that it is a tool designed to minimize the statistical effect of the natural gyrations and occasional extremes within such a series of numerals. But if this is an advantage, it is also, in its own way, misleading, and I decided to do a bit of number-crunching, using Mohonk's own data.

The snow chart shows a distinct jump to snowier winters beginning with the 1955/56 season, and for the next seventeen winters, through '71/72, annual snowfall averaged 77 inches at Mohonk. For the next sixteen years, through '87/88, it was down to 65 inches, and during the winters of '88/89 through '91/92, annual snowfall was an astonishingly meager 36 inches. We all remember that snow drought: winter sports depending on natural snow were practically non-existent, and children growing up during those years could not have imagined what a real Ulster County winter was supposed to look like.

Then came the eruption of Mt. Pinatubo in the Philippines, the greatest introduction of volcanic ash into the atmosphere since at least 1912 and probably since Krakatoa in 1883 (subject of a pretty awful movie some years back). Mt. St. Helens, by the way, was tiny by comparison. It is an accepted fact that eruptions of this magnitude cause significant short-term cooling due to the reflection of incoming sunlight, and can have unpredictable effects on atmospheric circulation patterns for a while. And so the four winters beginning 1992/93 averaged a hefty 81 inches of snow at Mohonk. But the next four seasons, '96/97 through '99/00, went back to a decidedly modest 50-inch average.

It is unclear what the underlying trend is since the Pinatubo effect finished playing out. The five seasons beginning 2000/01 spiked to 75 inches on average. The 2005/06 season had only 51 inches, and the present season, as of this writing, is virtually a bust. But any way you read it, the linear average of steadily increasing snowfall amounts would not seem to reflect the reality that snowfall peaked during the mid 1950s through early '70s.

I decided to review my own continuous record, going back to the winter of '65/66, of "major" valley snowstorms (with an arbitrary threshold of ten inches). These would not include major Shawangunk ridge storms that were moderate or even non-existent in the valley. I find that the nine winter seasons from '65/66 through '73/74 averaged 1.56 big snowstorms per season. The next eighteen winters, through '91/92, averaged only 0.28 major storms. The next four winters, the Pinatubo years, produced an average of 1.5 per winter, and the past ten winters, an average of 0.8. Once again, the years ending with the early '70s were the winners, especially if we discount the Pinatubo winters.

Now, some memorable events from my own records of winter in the Wallkill Valley. Many of you may remember some of these:

In late January, 1966, about a foot of powdery, wind-drifted snow; after the snow stopped falling, temperatures stayed frigid and the sky remained cloudy for three days, with gale force winds. I remember taking a walk along my road through a continuous shroud of thick, blowing snow, billowing over roof and treetops as a sustained 40 mph west wind continued unabated. The snowplow came through every twelve hours, but the road was passable for only an hour or two each time, before new drifts made passage impossible for another ten hours. This continued for two or three full days after the snow had stopped falling.

Winter of '66/67: five major storms, in what was the greatest seasonal snowfall on record at that time (116 inches). Three of these were March storms. One, in February, occurred when temperatures were at or below zero, with -20° the next morning. Winter of '69/70: Early in the season, a five-and-a-half-week period during which the temperature climbed above freezing only two or three times; fourteen mornings were zero or below.

Winter of '70/71: more than three months of continuous general snow cover (December 10-March 14). Winter of '77/78: The storm of February 6-7 was so deep and drifted that the snowplows gave up and nothing passed on the road for over 24 hours, till a bulldozer slowly came through and opened up a passage. Snow cover was never less than a foot from mid January till second week in March. The ice didn't go out over the dam at Wallkill till the night of March 21-22, which was also when the general snow cover finally became intermittent. Winter '78/79: in February, below zero on nine of eleven consecutive nights. Winter '80/81: in January, below zero on about ten of thirteen consecutive nights, including readings of –19° and –24°. On January 17, 1982, it never got above zero all day.

Winter of '92/93, beginning of the Pinatubo winters: The March 13 "Blizzard of the Century" saw sustained 50 mph winds all afternoon and evening. Numerous snow patches on the mountain into early May. In '93/94: forty days had readings of 10° or colder, of which seventeen were zero or colder, including -26° on January 21. Valley snow cover was one to two feet almost continuously from early January till mid March, and did not become intermittent till March 27. Numerous snow patches remained on the ridge till second week of May.

Conclusion: Despite the linear average component of the snow graph, it would appear that winter ain't what it used to be. Temperatures are milder, and extreme low temperatures are increasingly rare. Major snowstorms are less frequent, and snows are more often wet than powdery and wind-blown. Days with snow cover, especially long periods with continuous deep snow, are fewer. With increased global warming, and barring major new volcanic activity, it is probably inevitable that annual snowfall, which peaked from the mid 1950s through the early '70s, will continue to decline as more and more winter precipitation falls as rain. This is most evident in the valley, but will become increasingly the case on the Shawangunk ridge as well.

Those of us who enjoy a good blizzard and an old-fashioned cold, snowy winter should cherish our memories!

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