The October 4, 1987 snowstorm

Diabatic cooling occurs when melting snowflakes absorb heat from the surrounding air, causing the air temperature to subsequently drop. When precipitation comes down fast and furious with temperatures initially just above the freezing mark, the air can diabatically cool to the point where a cold rain can quickly change into a heavy wet accumulating snow.

If you were in Albany, NY, or nearby, you know this story:
From NOAA – Surprise October Snowstorm (October 4, 1987)

The earliest measurable snowfall at Albany, where 6.5″ inches fell, with as much as 20″ reported in parts of the Catskills. The storm wreaked havoc on the area because it was a heavy, extremely wet snow, which fell on fully leaved trees. Numerous branches and trees were felled…taking down power lines with them, blocking roads and damaging houses. Albany was described as “looking like a war zone.” Hundreds of thousands of people were without power…some for up to two weeks. It was the most snow that ever fell during the month of October in Albany. Many of those folks without power for a fortnight were in Dutchess, Ulster, and Columbia Counties, south of Albany.

It was just half a foot of snow; I’ve experienced much worse, including over two feet in March of 1993. But this was…weirder.

Beyond what I wrote here five years ago, I should note these:

*The storm took virtually everyone by surprise. Unlike the 1993 event, which you KNEW was coming, “the National Weather Service had forecast unseasonably cool weather and snow showers over parts of New York and New England, but there had been no talk of a walloping big storm.”

*The best description I’ve read about the surprise nature of the storm: “A process known as ‘diabatic cooling’ allowed temperatures at the surface to unexpectedly drop to the freezing mark during periods of heavy precipitation, and the end result was a very difficult situation especially given the lack of warning and consequent preparation. Diabatic cooling occurs when melting snowflakes absorb heat from the surrounding air, causing the air temperature to subsequently drop. When precipitation comes down fast and furious with temperatures initially just above the freezing mark, the air can diabatically cool to the point where a cold rain can quickly change into heavy wet accumulating snow. It’s a process that can surprise both forecasters and the public alike.”

*The friend I stayed with the first and fourth night (actually an ex-girlfriend) lost power for about two minutes, even though her place was less than a mile away from my apartment. FantaCo, where I worked, was less than 1.1 miles away; it never lost power for more than a moment, either

*Albany, Columbia, Rensselaer, Dutchess, Greene, and Montgomery counties were declared disaster areas, and the storm hit parts of New England as well
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Much more recent weird Albany weather