Breakthrough from the west


By meteomorris on 31 October 2017

There's a breakthrough from the west coming up. A storm depression with a core over the Norwegian Sea will attempt to bring cold polar air through the French Rhône valley to the Mediterranean next weekend. The cold air does not only bump into the French Alps, but will also pick up some extra moisture above the Mediterranean. The sea water is still around 20 degrees and this could result in fireworks! Not only in the French Alps, but also on the south side of the main alpine ridge. But, it's only Tuesday and the above is a forecast for Sunday/Monday. There is still a lot that might change, but I'll keep a close eye on the developments. In this forecast:

  • Sunshine after the storm
  • Reasonable snow cover in the northern Alps, no snow in the western and southern Alps
  • A breakthrough from the west next weekend?
  • Three scenarios that might bring snow

Sunshine after the storm

There were quite some extreme last weekend. Some snow came down in the northern Alps on Friday, the weather was pleasant on Saturday and pretty extreme on Sunday. The wind really kicked in. The atmosphere calmed down on Monday, but there's a lot of damage and the wind transported a lot of snow in the high alpine. Nevertheless, the conditions were great on the glacier slopes yesterday. You could find a layer of fresh snow in the sheltered parts of the mountain and the sun was shining. That will not be different the next couple of days. High pressure determines the weather, the sun is dominant and only the eastern part of Austria will see some clouds from time to time. You don't have to expect any significant snowfall though.

Reasonable snow cover in the northern Alps, no snow in the western and southern Alps

The above satellite recording is from this morning. It is great to see the low clouds (resulting from a combination of smog and forest fires) in the Italian Po valley, just like the residual clouds in the east of Austria. But the condition of the snow cover is striking. Only the peaks in the high alpine on the north side of the main alpine ridge are white. There's practically no snow in France or Italy and the western parts of Switzerland. Only the northern Alps got some snow lately and the snow cover over there is quite reasonable. Bad news for this winter? No, it's only the end of October.

Now is the time for winter to start, because snow in October is not an indication for the winter. The best dumps for a great start of the season come down in November (in the high alpine and the resorts in the main alpine ridge) and in December (on the lower parts of the mountain). The sun is still too strong in the beginning of the season and I've adapted my perfect season to it. I'll keep an eye on the development of the snow pack every day, which gives me the right information to head out for a nice PowderAlert in December.

A breakthrough from the west next weekend?

There is a breakthrough from the west visible on the weather maps since last Friday. Although the details change regularly, the basis is the same. It looks like this: there is a powerful storm depression developing above the Norwegian Sea, while at the same time there is still a strong high pressure area present on the Atlantic Ocean just east of the Azores. Between these two giants, there's a strong jet stream to the south gaining momentum. You can check out the jet stream on the map.

The jetstream forms the separation between cold air from the north and warm air from the south and will bring cold polar air south by the end of the week. You can see that on our 850 hPa maps for this week.

Three scenarios that might bring snow

Bovenstaande is een berekening voor over 7 dagen en dan kan er nog veel wijzigen. Grosso modo zijn er de volgende scenario's te bedenken.

All of the above is a calculation for 7 days and there's still a lot that can change. In general, these are the scenarios:

  • Stau from the (south)west: the moist air is moving south in this scenario, it will slowly turn to the west and will hit the French Alps at first. The real fireworks will start when the humid air moves from the Mediterranean to the Po valley and than hits the Gotthard and Ortler. In this scenario, there is still room for a small northern Stau. The snow line will be very high at first, but will drop thanks to the incoming cold air.
  • A retour d'est: in this scenario humid air flows through the French Alps towards Italy, but because the air stagnates and won't go further east, a Genoa low will remain resulting in snowfall for the Piedmont.
  • Stau from the north: in this scenario, the high-pressure area is located slightly further to the east and will push the cold air further east. The result is a northern Stau with no snow for France and all the snow for the north side of the Alps.

The good news is that there's a chance of snow in (parts of) the French Alps and that the first and second scenario will bring snow to (parts of) the Italian Alps. And those resorts can use some snow!

You don't have to expect any significant snowfall till the end of the week. If you want to see more and support wepowder, check out the wepowder Pro option. You'll get access to the snow maps for the next 14 days and much more!

Stay stoked, Morris

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