Snow in October?? Although it may be hard to imagine on a sunny and mild morning such as this one, we do in fact live in a part of the country where snow can occur just weeks after the end of astronomical summer. My next two blog entries will highlight a couple of exceptionally rare early season snowstorms that have affected different parts of Upstate New York over the last three decades, including a synoptic (large scale) event that dumped up to 22" of snow in the higher terrain of eastern New York back in 1987, and also a mesoscale (small scale) lake effect snowstorm that crippled the city of Buffalo just two years ago. Two entirely different events that developed under a different set of meteorological circumstances...but equally impressive nonetheless.
The snowstorm of October 3-4, 1987 was the earliest significant snowfall of the 20th century for the Northeast. Measurable snow fell across interior eastern New York, western Connecticut, western Massachusetts, and Vermont, accompanied at times by thunder and lightning. Snowfalls of greater than 10" occurred in New York's Catskill Mountains, and the highlands of western Massachusetts, extreme eastern New York, northwestern Connecticut, and southern Vermont. Slide Mountain, New York, reported 17 inches; Grafton, New York measured 22 inches; and Pownal, Vermont measured 18 inches. Measurable snow fell as far south as coastal Connecticut with 0.5" in Bridgeport. Power outages were extensive since trees had a full canopy and tree-related damage to automobiles and houses was extensive. There were 20 storm-related deaths and more than 300 injuries.
The storm was not forecast to produce such heavy accumulations of snow, but 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 a heavy wet accumulating snow. It's a process that can surprise both forecasters and the public alike.
Other than some of the higher elevations in Delaware County, nearly our entire viewing area "missed out" on this early season event because we were far enough west of the storm that what little precipitation fell was very light in nature, not allowing the atmosphere to diabatically cool down to the freezing mark. As much of an impact as the 1987 storm had, next week's featured storm had an even larger public impact as it affected a major urban center with more than half a million people! Be sure to check back!