Very similar story above Aberfeldy today, the pics could have been from
here (I had to check the text twice to make sure it wasnt).

There were no clouds around so it was dramatic, naturally i was in the
car sans camera.

Alan White wrote:
Some time ago there was a thread which discussed cloud formation
caused by fire on the ground and the resulting plume of heated air
rising and forming a cloud.

Today, we witnessed an excellent example.

http://www.windycroft.gt-britain.co.uk/060306_01.jpg was taken at
11:50, looking SE from the summit of Cruach a'Bhuic (635m), when we
first noticed that cloud was forming above the plume generated by
quite a small blaze on the hills above Helensburgh. (Cruach a' Bhuic
is the prominent lump on the skyline in the centre of the webcam
pictures).

http://www.windycroft.gt-britain.co.uk/060306_02.jpg was taken four
hours later from a much lower altitude. The blaze is now considerable
and the plume has sufficient energy to form a small, well developed
cumulus. What's interesting is that the smoke has spread sideways up-
and downwind with the main downwind component drifting out of the LH
side of the picture. The 'natural' clouds, by comparison have very
little vertical development. The photograph doesn't really bring out
the apocalyptic nature of the cloud which, given that the UK's nuclear
arsenal is stored just around to the right...