SRF Meteo warns of a dangerous situation on the roads. Jan Eitel explains why it is better to leave the car and bike parked early in the morning.
SRF Meteo warns of a precarious weather situation. What awaits us?
Jan Eitel: Snow clouds and drizzle are already on the way on Tuesday afternoon and evening. So there is some snow, especially between the foothills of the Alps and the northern edge of Switzerland. And you have to reckon with snow. However, the quantities are relatively modest.
Legend:
SRF
At the same time, drizzle is on the way in a lower cloud layer, which falls in the form of liquid, fine rain on the frozen ground. And so you have to reckon with slippery streets and sidewalks. This on Tuesday evening until around midnight. In the second half of the night it will be mostly dry.
But when does it get really dangerous? And why?
Warm and humid air will arrive from the west from early Wednesday morning. It starts to rain. The temperatures there are around -2 degrees, i.e. still below zero. That’s why it can happen in an initial phase that freezing rain comes about. So when warm air layers over cold air and rain falls into the cold air below, the raindrops can supercool. When the raindrops hit the ground, they freeze immediately, creating a clear, very smooth layer of ice. A veritable ice shell can even form.
So you have to reckon with black ice, generally on Wednesday mornings, in the eastern part of the country perhaps even into the early afternoon. Only from Valais to Graubünden and in Ticino does it mostly stay dry.
There is a real thaw on Wednesday afternoon.
After that the air is mild, about plus four or plus five degrees and there is also a brisk south-west wind. And then it rains far up, up to about 1400 to 1800 meters. So there is a real thaw on Wednesday afternoon.
How often does such a change in the weather occur where this freezing rain can also occur?
That can actually happen again and again in the winter months. Often, like this time, we have a cold phase with a few ice days like we have now. Temperatures below zero all day long.
Especially on Wednesday morning it will be precarious, even really dangerous.
And at some point warm, humid air will come from the west from the Atlantic in connection with a warm front. And then it slides onto this huge cushion of cold air. The liquid, supercooled rain then falls into the mighty cold air lake, directly on the ground and freezes into a layer of ice. Actually a not atypical phenomenon in winter.
What are your recommendations for Tuesday evenings and Wednesday mornings?
On Tuesday evening it will only be slippery in places due to snow or black ice. I think it will be precarious, even really dangerous, especially on Wednesday morning. And if it’s somehow possible, then it makes sense to work from home. But if you have to get out, it’s better to take the train or the tram – i.e. use the rails. Anything with wheels is better left standing. Because otherwise it will be a pretty big slide.
The conversation was conducted by Claudia Blangetti.