PA #1: Up to five meters of snow?


By meteomorris on 3 November 2014 · 0

More than 2 meters of snow the next 72 hours
More than 2 meters of snow the next 72 hours

After the lift-assisted powder on the glaciers, this is the first PowderAlert of the season. And this season starts with a bang! It will be a double or even triple stager that will bring a sh*tload of powder to the Alps. As I mentioned yesterday, the challenge is the temperature. It's quite clear that there will be lots of precipitation, but the snow line will be the biggest question mark. Is it worth it to drive down to the Alps? And is it worth it? Because warm air and cold air are pretty close to each other in the Alps, causing the snow line to go up and down from the valleys to the peaks. Next to the snow, there'll be also a lot of rain in the valleys and mid-mountain. You can expect 300-400 mm of rain this week, and this will cause flooding and devastation. Roads will be closed and some villages will be shut down for a couple of days.

Code red for the Italian Piemonte
Code red for the Italian Piemonte

This type of weather isn't particularly rare this time of the year. During the changing of the seasons, the water in the Mediterranean sea is still very warm, while the first cold air comes down from the northwest to the south. The collision of cold air from the north to the hot and humid air over the Mediterranean sea generally leads to powerful Genoa lows. Small storm depressions that occur locally, but can have a great impact on the weather in the Pyrenees and the Alps. Not rarely, huge amounts of rain and snow come down, where the combination of inflowing cold upper air, the warm Mediterranean sea and local orography provide an explosive cocktail. A phenomenon of which locals just keep talking about. Especially the role of the Alps, with its Rhone Valley and the Po Valley is not to be underestimated.

Up to 5 meter of snow the next twelve days?

Looking at the weather maps for the next 10 days, then there is something almost of disbelief in my eyes. Not one, not two, but three times snow from the southwest is coming towards the Alps according to the latest forecasts. An exceptional situation that we rarely experience. It's not really certain at the moment that this occurs, but it's that special that it's worth mentioning. Specifically because, if this scenario will occur, it could be possible that we have around 2 to 4 meters of snow in the high mountains of the southern French Alps, the Italian Piemonte, Haut-Valais, the Gotthard region, Ticino and the Upper Engadin on the weekend of 15-16 November. Locally even five meters. Imagine ... 5 meters of snow in 12 days time. Let's have a look at the scenarios below.

Event 1 (4-6 November): up to 200 centimeter of freshies

Storm Pia pushes cold air through the Rhone valley towards the Mediterranean, and that creates the Genoa low Qendressa. West of Qendressa is the cold air from the north. East the warm air from the Sahara. In this clash of the air masses immense precipitation is created and here you are ... the first dump.

Qendressa
Qendressa

Because anticyclone Quinn is holding stuff up to the east, Qendressa is only able to move very slow. The result is that the cold air can only reach the Alps with lots of trouble and initially it will be mainly orographic effects that will cause the snow line to drop. The expected snow line will be between 1500 and 2300 meters, and the freezing level will be around 2500 meters. Snow for the higher alpine it probably is.

The first dump

It is typically fine-tune in the last minute, because it's the details that do the trick. If we look at the weather map of Wednesday we see a wave in the front line. A front that is primarily blue, but red at the green arrow. It's trying to keep the warm air there, causing the snow line south of the Simplon, Monte Rosa, the Engadin and the Piedmont to be around 1700-2300 meters. And that's high.

Waves in the front
Waves in the front

On the other hand cold air is flowing in from the west on Wednesday. What means so much that the snow line begins to drop from the west. Especially in the Swiss Valais and the Gotthard region they seem to benefit from this situation. You don't have to expect that much snow, but probably 25-50 cm dry powder at 2000 meters and higher up even more. In short, lots of snow above 2500 meters (75-200 cm), locally 20-50 centimeter above 2000 meters. But ...

Temporarily warmer

Friday are the Alps in warm air again. The freezing level rises towards the 3000 meters and with the moisture still in the air a lot of snow will welt. But the heat is short-lived.

Event 2: (9-12 November): again up to 200 centimeters of freshies!

It's just like event 1 with cold air coming in from the northwest, a Genoa low as a result and snow for the southwestern Alps and southern Alps. The same type of event, but a bit more promising. According to current calculations there will be more cold air, which causes the snow line in the Piemonte to drop to around 1400 meters or even lower.

Calculations 10th of November
Calculations 10th of November

Event 3: (12-14 November): Another meter of snow?

Too far away to say anything reliable, but certainly worth mentioning. Because the map below shows more snow from the southwest. Far too early for details, but only imagine.

Calculations 13th of November
Calculations 13th of November

Conclusion

Lots of snow in the higher alpine next week. The trailing front puts the freezing level pretty high and the warmth of Friday and Saturday are not pretty good for the snow quality. Not the time to travel to the Alps, but it's perfect snow for a nice base for the rest of the season.

Especially because event 2 and event 3 will also bring snow. Would the weekend of 15-16 November the first weekend for non-glacier areas to open their lifts? Would that be Montgenèvre and Sestriere? Or is it time to do some touring Via Lattea and Queyras? For now it is still speculation, but it seems that we can really put our gear ready. I already block the second weekend of November. Live updates from the Alps on Wednesday, where we follow the dump and rain inferno closely.

Stay stoked

Morris


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