The first Nordstau of the season!

It’s finally September again, which means wePowder is back after a summer break! In the following weeks I will keep you informed of the first snowfall events and from October onwards, we will start again with the weather reports on Mondays, Wednesdays and Fridays. After a hot summer in the Alps, winter seems to be approaching fast. The past few days we already saw the first snow above 2500 metres, but now we even see the first Nordstau appearing on the weather charts before the end of the week!

In this weather report:

• Ex-Danielle causes very high temperatures
• Weather change with establishing northwest flow
• Nordstau with possibly a lot of precipitation
• Persistently cold

Very warm

Before we see some fresh snow, it will be very warm again. On the eastern flank of ex-hurricane Danielle, which lies off the coast of Portugal, a lot of warm air is being transported towards Central-Europe. Today, in many places, it is already causing maximum temperatures of around 25 degrees, but tomorrow it will be even warmer. In the Western Alps, temperatures of locally 30 degrees are possible and in Austria temperatures will rise to (well) over 25 degrees. It will also be particularly mild at higher altitudes. The freezing level could temporarily be at around 4000 metres. The sun will have more difficulty from Tuesday afternoon onwards, due to the supply of some Saharan dust and high clouds.

Weather change

However, this warmth will not last long, because from the middle of the week the weather will slowly but surely change. Wednesday it can still be quite warm, but in the Alps it is a lot more unstable, which can cause more (thunder) showers in the course of the day. On the north side, especially in Austria, it might stay dry a bit longer due to the föhn, but even here it will most likely not stay dry.

Northerly flow

From Thursday onwards we see the real changes on the weather charts. For that, we won’t focus on ex-Danielle, but more on the low-pressure area that deepens and stays over Scandinavia. From the end of the week, a high pressure area settles around the British Isles which opens the door for a strong northern flow towards the Alps. In the course of Thursday, the wind will increasingly turn to the northwest and a cold front will reach the Northern Alps. As it is still quite warm, the snow will be limited to the high mountains. The snowline will be around 3000 metres.

Friday, the strong north-westerly flow will bring in more and more cool air and the stau will keep on bringing (light) snow. In the evening, the snowfall will intensify and we’ll see a decreasing snowline to around 2000 metres, on Saturday morning even to around 1500 metres in the Northern Alps! It looks like the Nordstau will continue until the weekend. Higher up, we can expect serious snow accumulations for the first time, but how much snow it will bring is still uncertain. For now, I expect some 30 centimeters up in the northern (western) areas like Engelberg and the west of Austria from Friday morning, but things can still shift here. Also, I certainly don’t exclude higher snow totals over a larger area! Later this week I will give a short update on the expected snow amounts.

Ski resorts like Hintertux and Zermatt will gradually open (more) lifts and other glaciers will also be preparing for their ski openings in mid/late September. In any case, the snow is badly needed, because on many glaciers in the Alps all the snow has completely melted, even in the accumulation areas!

Cold after the weekend

The strong cooling caused by this northerly flow is clearly visible in the ensembles. We plunge from temperatures far above average to well below average. Also after the weekend it will remain cold. For now, the Alps seem to be in the northern flow until at least the end of next week, but the precipitation signals are clearly decreasing. The Eastern Alps seem to benefit the longest from the Nordstau.