Our weather is determined by the alternation of high and low pressure areas. High pressure usually means nice weather. In summer, a high pressure usually causes nice and warm weather, whereas in winter it means nice but cold weather. Low pressure areas bring the longed-for snow, provided the air masses are cold enough. High pressure areas rotate clockwise around their core, while low pressure areas rotate anti-clockwise in the northern hemisphere. A low usually consists of two fronts: A warm front moving ahead provides moderate but long-lasting precipitation. The warm front is followed by a more rapidly advancing cold front, which tends to catch up with and "consume" the warm air. When warm and cold fronts mix, this is referred to as a mixed or "occluded front".
Cold fronts cause typical showery weather, with localized but heavy precipitation on a small scale.
Cloud accumulation and heavy precipitation
On the windward (windward) side of mountains, cloud accumulation often causes particularly heavy and abundant accumulation precipitation. This is because humid, cloud-rich air has to release some of its moisture there. As warm air can absorb considerably more moisture than cold air, and the air cools as it flows over a mountain range due to the uplift, excess water falls to the ground in the form of snow. A particularly well-known example of such a "cloud dam" is the Arlberg, which is popular with powder fans. You can see the cooling effect particularly well when your breath condenses into clouds of steam in the cold winter air. The warm and humid exhaled air cools down quickly and can then bind much less moisture - small clouds form.
The heaviest snowfall occurs at temperatures around O° C. The snow line is around 300 m below the zero degree limit. "Real" powder falls in small flakes at low minus temperatures. Experienced weather observers can often predict the weather surprisingly well (or be completely wrong...)
with the help of data published on the web, cloud cover, a little "intuition" and knowledge of the area.
