It has been snowing heavily in the southern French Alps since Thursday morning. An active low pressure area is currently moving from the southwest into the Alps bringing lots of snow for the southern French Alps and the Italian Alps. There will be a cold front with some snow for the northwest and north coming in in the night to Friday, but don't expect too much from that. PA # 23 is in effect from Thursday and we can get ready for PA #24 this weekend. Cold air descends from the east towards the Alps. At the same time, a storm depression arrives in the western Alps from the west. And where cold air and moist air meet, snow will fall. In this forecast:
It's been snowing in the southern French Alps since Thursday morning. An active depression over the British Isles with a sub-core close to the Alps is causing a stiff south western to southern current with a lot of snow. It looks like this:
The result is PowderAlert #23. You can expect 20-50 cm, locally 60 cm above 1500 meters in the regions below:
Friday will be a powder day. It was already ON this Thursday in the south of the Ecrins and the bordering areas in the Italian Piedmont. By the end of the afternoon it was also ON in the other reginos. The alert is still in effect in those regions on Friday. It remains cloudy in the east for a long time, but the day starts sunny in the western Alps.
Something special happens on Friday. A storm above the Pyrenees that looks meaningless at first sight is heading towards the Alps (see the black arrow above). At the same time, high pressure from the east is picking up, thus squeezing the further supply of storm depressions from the Atlantic ocean. Because the pressure is increasing north of the Alps and this small storm can transform itself into a larger storm south of the Alps, it results in the image below.
High pressure (H) north of the Alps and low pressure (T) south of the Alps. Between these two cores there is a strong eastern current (the big blue arrow). This brings in air from Siberia and that will be cold. At the same time, there is moist and mild air south of the Alps (the red arrows). The cold and mild humid air will collide exactly above the Alps this weekend.
The air is first and foremost pretty mild on the south side of the Alps on Saturday. The cold air is still too far north, but it will move south in the course of the day. The cold air is expected to mix with the humid air from the Adriatic Sea and the Mediterranean in the course of Saturday. This results first of all in fresh snow from the west to the southwest during the night from Friday to Saturday. It will snow south and west of the Ecrins, in the Italian Piedmont and the northern French Alps. The snowfall will spread to the rest of the Alps later. The biggest question marks for now is where the snow line will be located. With a swaying front above the Alps, various layers of air (one cold, the other warm) mix with each other. So it depends a bit on your position in the Alps where the snow line will be located. Take into account 1000 meters, locally higher, locally a bit lower.
I expect the most snow south of the Alps where humid air, orographic cooling and the cold air will come together this weekend. That means PA #24 will be ON this weekend. Because it is all very dynamic at the moment and a small shift of the hot or cold air can have major consequences, I'll wait for tomorrow with my exact tips. Do you want to book something for this weekend then I would choose one of the options below:
It's snowing there right now, snow already came down and there's some more in the forecast. The chances for snow on the southern side of the Alps remain very high even after the weekend when a Genua-low of Adria-low will be formed. A new update with hopefully more tips where to go next weekend tomorrow.
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