La grande nevicata del 9 dicembre 1990 su Piemonte e Valle d'Aosta

#MeteoAmarcord - December 9, 1990: heavy snowfall in the Northwest, 1 meter in 24 hours in Aosta and Cuneo. The Turin-Juventus derby has been postponed due to snow. 35 years ago, at this very moment, Northwest Italy experienced one of the heaviest snowfalls of the last century, locally even more intense than the infamous historic events of 1985-1987. The snowfall of the Immaculate Conception of 1990 was preceded by a cold wave that brought minimum temperatures close to -10°C in the plains, quickly followed by the descent of an Atlantic trough—with cold air of polar-maritime origin—which favored the formation of a depression between the Gulf of Lion and the Ligurian Sea, with a minimum pressure of up to 995 hPa. A classic "cold pillow snowfall" pattern, with moist, temperate air from the south at high altitude flowing over a cold air mass at ground level, resulted in widespread and intense snowfall across the entire northwest, with the heaviest snowfall in the central-eastern Aosta Valley and lower Piedmont. Aosta-Saint-Christophe Airport (544 m above sea level) recorded the heaviest snowfall (in 24 hours) since 1891, with a full 100 centimeters of fresh snow, an accumulation that actually exceeded the annual average of 92 centimeters. But the highlight of the snowfall occurred in the Piedmont Alps, with over two meters of snowfall in the Pennine Alps (222 cm in Carcoforo (VC), in Valsesia, and 209 cm in Macugnaga (VB), Anzasca Valley, both at approximately 1,300 m above sea level). At low altitudes, the heaviest accumulations occurred in the provinces of Cuneo, Asti, and Alessandria: in the city of Cuneo, fresh snow reached 120 centimeters, 105 of which fell in just 24 hours, setting an all-time record for daily accumulation since 1877 and well above the previous record of 68 cm/24 hours set on January 14, 1969. In the city of Alessandria, 85 centimeters fell, 72 in Tortona, 65 in Novi Ligure and Ovada, and 55 in Casale Monferrato. In the Asti area, snowfall reached 60 centimeters in the city of Asti, 55 in Canelli, 40 in Villanova d'Asti, and a full 100 in Roccaverano, in the upper Langhe. Snowfall was less abundant in the central-eastern and northern plains of the region, with about 20 centimeters in Verbania, 22 in Turin, 28 in Vercelli, and 31 in Novara. Frizzy days followed, aided by a temperature inversion, which characterized the entire second ten days of December, with minimum temperatures reaching -18°C in Aosta and -15°C in the plains of lower Piedmont, thanks in part to the abundant layer of snow on the ground. Further details and data on the event can be found on the DatiMeteoAsti website. [Thanks to TGR Piemonte for kindly providing the video in collaboration with RaiMeteo and RaiTeche].