Formation of altocumulus clouds due to an unstable airmass at upper levels and also producing snow (precipitation) which has not reached the surface because of the presence of an extremely dry airmass at 700mb as indicated by the weather sounding (2nd thumbnail). The formation of such cloud was made possible because of the introduction of a warmer airmass at 500mb (3rd thumbnail) after the passage of the 536mb line. At the surface, a cold and dry wind was still blowing over the Maltese Islands at the time. The NW wind was originating from very cold Balkan Peninsula. The presence of this cold airmass could be proved by the temperature map at 850mb (4th thumbnail).