October is a good month to discuss the seasonality of snow and how it affects the start of the ski season, availability of powder during winter, and the possibilities for late freshies in the spring.
October, especially early October, is one of the few months that one might feel a ping of jealousy for skiing outside of the Cottonwoods. In the Alps, storms blanketing the high elevations often improve snow conditions on the lift-served glaciers, as has is happening currently.
Good news for the glaciers as further snow falls across many higher parts of the Alps: https://t.co/PGoKdcOhGN pic.twitter.com/kD9D0PWlyZ
— weathertoski (@weathertoski) October 4, 2021
Skiers tend to focus on mean-annual snowfall, but the seasonality of snow is also a very important snow climate variable. Below is a graph showing the mean annual snowfall at Alta, Sukayu Onsen Japan (in the Hakkoda Mountains of northern Honshu), and the median snowfall Sonnblick observatory in the Austrian Alps (the mixture of mean and median reflects what is readably obtainable online).
Alta averages about 510 inches of snow annually, but it has ramp up in snowfall in October and November,a broad winter maximum from December through March with average snowfall each month very near 80 inches, and then a ramp down in April and May. In part this reflects the seasonality of the storm track, which shifts equatorward in the fall, provides inland penetrating Pacific storms in the winter, and then shifts poleward in the spring. As a result, monthly liquid precipitation equivalent (not shown) from December to March is between 6.3 and 7.1 inches, whereas during July and August it is less than 2 inches. A secondary factor is the temperature seasonality, which results in a greater fraction of precipitation falling as rain instead of snow in the shoulder months, especially October and May.
In contrast, Sukayu Onsen, which averages about 694" of snow annually, exhibits a much sharper wintertime maximum in January of 180". Snowfall in October is much lower than at Alta and in November it is comparable. Sukayu Onsen is actually quite wet in those months, averaging over 7" of liquid precipitation equivalent, but most of that precipitation falls as rain. However, from December to February, when temperatures are lower and cold-air outbreaks from interior Asia are frequently occurring over the Sea of Japan, snowfall is frequent and intense. The Japanese mountains near the Sea of Japan are the surest bet for powder skiing in January, but the season gets a later start than some other parts of the globe. In Japan, the best option for earlier skiing is probably the Hida Mountains near Hakuba which are much higher than the mountains of Hokkaido or northern Honshu.
Sonnblick in Austria is located at over 3000 meters and the highest year-round operated observatory in the world. Due to latitude (47˚N) and altitude, it can observe snow any month and a large fraction of the precipitation from October to May falls as snow. Liquid precipitation equivalent seasonality in the Alps is relatively muted and Sonnblick observes 5 to 6.5" of liquid precipitation equivalent in each month from December to August. September, October, and November is their dry season, although even in October they average more than 3" of liquid precipitation equivalent (Note: this should not be generalized for the Alps as a whole as some areas of the Alps are wettest in the fall). Snowfall, however, peaks in December and March, with a small decrease in January and February, which reflects a slight decrease in liquid precipitation equivalent in those months at this elevation (this should also not be generalized for the Alps as a whole).
The above comparison illustrates some of the intricacies of snowfall seasonality at three mountain locations. Some ranges, such as the Alps in Europe and the Himalaya/Karakorum in Asia, exhibit dramatic regional variations in this seasonality as well, which should be considered for ski or mountaineering planning.
interesting!
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