You can often read about the northern French Alps and southern French Alps in the weather forecast, but that sometimes raises questions. In this article I'll try to explain what the difference is between both regions and why there's a distinction in the first place.
With the French Northern Alps we mean the mountains in the Haute Savoie, the Savoie, the Isère and the mythical resort of La Grave. It's a region with big valleys (Grésivaudan, Maurienne, Tarentaise, Vallée de l'Arve) and fairly large cities (Grenoble, Chambéry, Annecy, Annemasse, Albertville, Cluses, Saint-Jean-de-Maurienne, Bourg-Saint-Maurice, Chamonix-Mont-Blanc).
Here you will find very large ski areas such as Les 3 Vallées, Portes du Soleil, Espace Killy, Paradiski, Chamonix Mont Blanc, Alpe d'huez and Les 2 Alpes. But also smaller and more traditional ski areas such as La Sambuy or Bonneval sur Arc.
Most of the snow that comes down in the northern French Alps comes from the west or northwest. Snow from the southwest often results in a Föhn or rain with a snow line at high altitude. Snow from the west to west-northwest reaches the entire region, but it's hard for snowfall from the northwest to north to reach the Haute Maurienne and La Grave. On the other hand, the Haute Maurienne and the eastern part of Val d'Isère often benefit from a retour d'est. Especially the higher parts of Valfréjus and Val Cenis profit a lot from this weather phenomenon.
The ski areas in the west of this region are often situated at lower altitude and that's what we call the pre-Alps. The season often starts a bit later and ends somewhat earlier because it's easier for the warmer air masses from the Atlantic Ocean to reach these parts. If you go deeper into the Alps, the summits become higher, the valleys become narrower and the terrain more rugged. Especially once the cold air has settled itself in the upper valleys of the Haute Maurienne, Haute Tarentaise, but also the Chamonix valley, it will be considerably colder. The cold air creates micro climates that can be the difference between rain or snow in the middle of winter.
Well-know snow magnets in the French northern Alps (when the current comes from the west to northwest are:
The division between the northern French Alps and the southern French Alps is clearly visible on the maps when the current comes from the west-northwest. Clouds and snow generally don't cross the line south Vercors - Col the la Croix-Haute - the southern peaks of the Dévoluy, the col Bayard - the southern peaks of the Ecrins - Col du Lauteret - Mont Thabor -Bonneval sur Arc. That looks something like this.
You can easily see the difference between the northern French Alps and the southern French Alps. There are clouds and fresh snow in the French northern Alps and it's sunny and dry in the southern French Alps. The northwest of the Hautes Alpes tends to pick up a bit more snow, but you don't have to expect any precipitation more to the south and east.
With the French Southern Alps we mean the mountains in the Hautes Alpes, the Alpes-de-haute-Provence, and the Alpes Maritimes. Not many people live in this sunny region where you can already feel the vibe of the Mediterranean. The largest city is Gap with 44,000 inhabitants, but another mentionable city is Briancon with 12,000 inhabitants (and direct access to the slopes). You can find some famous ski resorts in the southern French Alps such as Serre Chevalier, Montgenèvre, Vars-Risoul, Praloup and Isola 2000. But also relatively unknown small gems such as Saint Véran, Abriès, Pelvoux or Crévoux.
Most of the snow that comes down in the southern French Alps comes from the west or the southwest. A current from northwest to north often causes a cold wind from the north. Snow from west to southwest reaches the entire region, but snow from the west sometimes finds it hard to reach the resorts in the east of the Queyras. However, those resorts pretty much always profit from a retour d'est, especially resorts like Saint Véran, Abriès and Isola 2000.
These areas get less storms to process, but once a storm passes, it brings a lot of snow. In this region, the transition from a beautiful (Indian) summer to winter can be abrupt, especially in the areas deeper in the Alps. When the first winter storms pass in November and cold air can settle in the narrow valleys, summer is over. On the other hand, the season is long and it might take a while in spring before it starts to look and feel like summer again.
They might have less storms to process, the dry air preserves the snow very well and it stays fresh for a long time. Another advantage of the southern Alps are the many larch forests. There are a lot of slopes that grow larch trees up to an altitude of 2200 and 2400 meters, which are perfect for the better tree runs.