The airport of Caernarfon lies on a promontory, surrounded by sea on three sides. On the approach to runway 08, the mountains of Snowdonia tower in the background. On this day, perfect visibility over the Irish sea is interrupted by a wall of moisture running NW-SE, capped by an inversion layer just level with the peak of Snowdon (3560'). Cloud spills over the ramparts of the great mountains from the East, while inside the wall visibility is 5 miles at best. Hazardous conditions for a little aeroplane...