High pressure haze

Met office chart - high pressure

We're in the middle of a high pressure weather system - a 'blocking high'. Stable high pressure is more common on continental land masses, low pressure with its weather fronts and instability comes to us from the Atlantic. Sometimes the high pressure stays still and blocks the weather from the sea, giving us warm temperatures and light wind. The high pressure sits like a cap, holding down any dust, smog or vapour, so it can usually give us quite hazy and indistinct visibility especially later in the day - which is not so good for photography. 
So as we found on Friday, we have to work with the conditions. Hazy visibility can allow us to use longer (telephoto) lenses that actually exaggerate the haze, which gives a sense of distance. Haze is a distance cue - it indicates that something is far away. More haze can suggest greater distance. Long lenses flatten the perspective, which makes foreground and backgrounds - such as mountain horizons - stack up on top of each other and appear to continue forever. The haziness can also give a soft, pastel single colour effect too, leaving you with simple colour shapes to arrange in your picture frame.

Telephoto shot in Glencoe in hazy mid-day light

Often the weather can be claggy, foggy and unpleasant, especially if north sea fog comes in, and this can  give us one of the most spectacular effects - the temperature inversion and its cloud sea. Cold damp air stays low, but on the hill tops it is actually warmer and you can emerge above the clouds. 
It is worth checking the met office, whose mountain forecasters seem to have an interest in photographic weather conditions, to see what's happening during a high, and if an inversion is forecast, get up as high as possible.

Cloud sea in the Cairngorms

A happy state of affairs