A northern Stau by the end of the week?


By meteomorris on 1 October 2017 · 0

The models are going up and down in the meteorological autumn. It can feel like summer one week and you can really feel that winter is coming the next. It won't be any different next week. The temperatures will reach around 20 degrees in the Alps this Wednesday, but it will drop to around 10 degrees in the Swiss and Austrian Alps on Friday and Saturday. This is all caused by a jetstream from the north that will be positioned around 400 kilometers more to the west than was calculated before. Friday is still far away and nothing is more dynamic than the weather, but if the calculations are right the north side of the Alps can expect some snow in the second weekend of October.

  • September colder than normal
  • Mild temperatues, colder on Tuesday
  • Temperatures will drop on Friday and... precipitation

September colder than normal

The meteorological autumn is on its way for a month now and it all started hopefully. It was colder than normal than average, significantly more snow than usual came down and the glaciers are white again. The map below shows how much colder September was than usual.

Much colder in central Europe
Much colder in central Europe

Central Europe had to deal with cold air for weeks because of a meandering jet stream, and it sometimes was 6-8 degrees colder than usual. It's striking that the Weissfluhjoch in Davos (Switzerland) had 15 days of snow in September. And yes that's a record (it's being measured since 1955). On the other hand, it's still not even early season. The sun is still high in the sky and a lot of days are simply mild. The most snow that came down in September already melted. And that's okay, because early snow isn't always a good thing. We've seen early snowfall in September and October the last couple of seasons but that was followed by no precipitation at all for a long period. The resorts in the Alps had to open with mostly artificial snow the last three seasons.

I don't really care about artificial snow, but I'm more concerned about the October snow that sticks around on north faces in the high alpine. That snow faceted (because of the sun and the long period without precipitation) and formed a lousy base for the rest of the season. We've seen too many avalanche accidents the last couple of seasons that happened because of the poor winters and the lousy base layer... That's the reason why we're monitoring the snowfall right now. Not to get you at there in October, but to inform you what's happening so you can make better decisions later this season.

Mild temperatues, colder on Tuesday

It's still mild in the Alps the next couple of days, with some dropping temperatures on Tuesday. A front touches the Alps bringing some precipitation, but it will only come down as snow in the high alpine. The weather will be mild, sunny and dry on Wednesday and Thursday. It's a true Indian Summer.

Temperatures will drop on Friday and... precipitation

According to the latest calculations, the high-pressure area does not stand and a strong current from the north will take over on Friday. That is if the calculations right now will be right. I can probably tell you on Monday/Tuesday with more certainty if that northern Stau will actually kick in or if the high-pressure area will stick around. Check out the two comparisons of the past 48 hours below where you can see the uncertainty. You're looking at the calculations for this Friday.

High pressure above the Alps
High pressure above the Alps

Strong current from the north
Strong current from the north

The weather is still subject to change the next couple of days (what's new), but it's interesting to look at the ensembles. You can see the low temperatures coming on Tuesday on GFS, but also the rapid drop in temperature on Friday. That drop is not as strong on GFS, but normally rapidly incoming cold air causes a lot of precipitation, because the hot and humid air has to cool down quickly.

GFS for the northern Alps
GFS for the northern Alps

Check out the ensembles of ECMWF. You can both see the drop in temperature, as the peak in precipitation on Friday.

Drop in tempature
Drop in tempature

Peak in precipitation on Friday
Peak in precipitation on Friday

This all corresponds with our snow maps this morning. You can see the drop in temperature and the snowfall in the northern Alps on Friday. But again, the models are dynamic and we'll see how it will develop the next 96 hours. It will be an interesting week!

And pssst, the wePowder shop is online.

Stay stoked
Morris


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