Both this image and the first thumbnail photo show an extensive area of bright white cloud without shading formed from the spreading out of contrails under a very cold upper-level airmass above 7km with a 100% humidity level. The cloud was of the genus Cirrocumulus, consisting of small elements with an apparent width of less than 1°. These upper-level conditions are very ideal to produce such long-lasting aircraft contrails which gradually spread out transforming into Cirrocumulus homomutatus. The weather situation was practically the result of a rare split polar vortex as shown in the 500mb chart on the third thumbnail that was about to send an out of season upper-level trough towards the Mediterranean generating a low pressure system. Such widespread high-level clouds which were photographed here are the first to form in a bad weather system acting as clear harbingers of bad weather.