“Avalanches can be triggered when some slightly careless skier goes to the slope and moves a little bit of snow,” Schäuble said in Berlin on Wednesday evening.
It was impossible to tell at this point whether the avalanche had reached the valley floor or was still in the top third of the slope, he added.
The comments were a rare statement of position from Merkel's finance chief Schäuble, who has until recently confined himself to comments on the affordability of the refugee crisis.
Europe could only resolve the migration crisis by working together to face the “rendezvous of our society with globalization,” Schäuble said, adding that Germany could not solve the problem by itself – even by closing the borders between its federal states.
Either that, “or it can become extremely bad for all of us”.
But Schäuble's party colleague Volker Kauder, leader of Chancellor Angela Merkel's Christian Democratic Union (CDU) MPs in the Bundestag (German parliament) was more optimistic.
“Angela Merkel has for a long time had a clear plan for how we should react to the movement of refugees such that it doesn't damage Germany in the long term,” he told the Schwäbische Zeitung on Thursday.
“She's following up the points that are necessary for that. I don't see that there's any underhand change of course.”
In recent days, Germany has tightened its refugee policy, re-introducing the so-called “Dublin rules” for Syrian refugees, which would see them sent back to the first EU country they entered to apply for asylum.
Last week, Sweden asked refugees on their way to the Nordic country to stay in Germany as they were hitting their limit for accommodating migrants.
And Merkel faced a mini-rebellion over the weekend from her Interior Minister Thomas de Maiziere when he announced his own plans for stricter policies, apparently without the backing of other senior officials.