Surprising Retour d'Est in Piedmont

In my previous weather forecast on Monday, I already mentioned the snowfall that was going to fall in Piedmont today, but it was still quite uncertain how much it would be exactly. In the past two days the weather models have come to an agreement and they have increased the snow amounts. Time for the first Retour d'Est of the season!

Depression over the Mediterranean

The depression over the Mediterranean Sea has caused already strong precipitation and flooding in Southern Italy and today also in Corsica, but now also the South-western Alps are under the influence of this low pressure area. The behaviour of this depression was difficult to determine during the past weekend. On Monday, I already mentioned that with a moist southeastern flow snow would be possible today in Piedmont, but in the last 48 hours all models have turned in the positive direction and suddenly show way more snow.

Let's have a look at the different weather models:

• ECMWF: The European model is going all out and predicts more than half a metre of snow, especially for the southern regions.
• GFS: The precipitation in the American model seems to be more uniformly distributed, but this is because this weather model has a rather low resolution. Small-scale differences are therefore not visible in this model.
• ICON: Two hotspots are visible in the ICON model. The snow amounts have been slightly increased compared to yesterday and are now similar to the European model.
• ARPEGE: The ARPEGE model of Meteo France shows the most precipitation with again the two hotspots of the Alpi Marittime and the Cottian Alps. According to the model, up to a metre of snow could fall by tomorrow. It's not impossible, but in my opinion this seems a bit on the high side at the moment.

To summarise: half a metre of snow is possible in the two hotspots Alpi Marittime with areas such as Limone Piemonte and Queyras - Monte Viso (Cottian Alps) with areas such as Prali. In the stau areas this can be locally even more. For France, as usually is the case with a Retour d'Est, the eastern parts of the Queyras and Haute-Maurienne regions are the only French areas that really benefit from this snowfall. Due to the föhn, the other areas remain dry and mild. Locally, the temperature can rise to around 15 degrees.

High snowline!

The snowline is still a bit of a problem with this snowfall. The south-eastern flow will bring a lot of warm air to Piedmont. During the day, the snowline will rise to an altitude of about 2500 metres, so in regions like the Alpi Marittime only the peaks will get the larger amounts of snow. However, especially in the narrower valleys, the heavy precipitation may cause precipitation cooling and the snowfall will be a few hundred metres lower for a long time.

Second wave of precipitation during the weekend?

A low pressure area over France will cause some precipitation in the Alps from Saturday on. Exact details are still hard to determine, but Piedmont might get a second Retour d'Est within a week. In the Northern Alps, a cold front will also bring some fresh snow.