I looked up when the sun comes up in Basel (where I live) and found out it's at 7:18. Later I did some googling to see if anyone else had noticed this and came across this article about something similar happening in 2008. It mentions polar stratospheric clouds as a likely cause. The following evening however, I didn't notice anything remarkable. And as I write this the next morning, The sun has now been up for an hour but due to clouds it looks darker than it did an hour and a half earlier in the morning yesterday.

So I'm wondering, what is the cause of this unusually bright morning twilight? And can I expect to see it again in the coming days/weeks/months?

Something that might relate to this is the siberian winter that seems to await Europe.

_{PS: I also wouldn't be averse to other people around Europe confirming that they also noticed this.}

Unfortunately, I'm not aware of any stratospheric forecast products for these clouds. The closest thing is an analysis of the 450 K $\theta$-surface showing area within the polar vortex with temperature at or below -78 C. These depict the area within the polar vortex that are favorable for polar stratospheric clouds. However, these do not show where the favorable area is, nor give an indication if these clouds will actually form. You can view the northern hemisphere plots here. The other stratospheric products deal with the size of the polar vortex, UV-B penetration and ozone analysis which do not aid in the forecast of these clouds.