Let me get straight to the point: we have to bite the bullet this week in the Alps. Until Saturday in particular, quite a lot of precipitation could fall in the north-west Alps, but with a snowline that could reach 2,500 metres altitude and also stormy winds higher up. So, although the snow cover up there will grow, the lower areas just before Christmas will have to deal with this almost annual spoilsport: the "Weihnachtstauwetter".
Most precipitation passes north of the Alps today and tomorrow. Especially the areas on the northern edge in the north-west Alps will be affected by this precipitation. Deeper into the Alps, it will remain mostly dry. The snowline is mostly around 1,700 to 2,000 metres. In most areas, not much more than 5 to 10 centimetres will fall today. Tonight, a new front will reach the northwest Alps and the westerly winds will pick up considerably. Higher up, we can expect wind gusts of over 100 kilometres per hour, especially on the exposed peaks on the northern edge of the Alps. Tomorrow too, the extreme northern areas should expect some precipitation, but the rest of the Alps will remain generally dry.
Friday will be rough and tumultuous. A warm front will reach the Alps during the night from Thursday to Friday. An active precipitation area hits the north-western Alps from the west. Until Saturday morning, 80 to maybe 100 centimetres of snow could just fall around the Mont-Blanc massif, but with the warm front, temperatures also rise dramatically! In the French Alps, the snowline rises to around 2,300 to 2,500 metres! On the north side, the snowline will also be (well) above 2000 metres on Friday.
Most precipitation may fall in the stau areas of the north-western Alps, around 30 to 50mm with locally also outliers possible. Below 2000 metres, most of this will therefore come down as rain. For powder, you would have to look considerably higher up, but with another stormy wind on Friday, higher up many ski lifts will most likely remain closed and the avalanche risk will also increase again. So conditions here are far from ideal. The strong westerly flow makes for very turbulent weather. Still want to go out? Then maybe look rather for the areas in the rain shadow, for example in the South(-eastern) Alps. You won't find fantastic powder conditions here, of course, but at least these areas keep it (mostly) dry.
Ensembles of ECMWF and GFS for Grenoble (wetterzentrale.de)
The developments for the days after Christmas are still very uncertain. According to the European model, a cooling seems to become slightly more certain, but the degree of cooling is still very unclear and is already somewhat disappointing compared to the runs of the past few days. Also, this possible cooling does not seem to be accompanied by much precipitation either. However, the American model does not want to know about this temperature drop yet and shows temperatures well above normal until New Year's Eve.