Ac cas clouds, in Maltese known as `Dahar il-fekruna`, indicating a change in the weather, in this case the arrival of a Mistral wind bringing a cooler airmass. These clouds formed at a height of between 3.1km and 5.1km in a steep but rather dry airmass background due to the arrival of a developing cold front lifting the airmass column. These clouds did not produce any rain or thunderstorms due to convective inhibition and indeed the upper-level dryness of the airmass involved.