In theory, Mickle Fell is an ideal ski ascent, approached from the north from Cauldron Snout. However, there are no rights of way and almost the whole route lies in the army's Warcop Training Area. While, in good snow cover, as noted in the Access section, trespass may not be a concern, even low flying over an army training area is frowned upon, and unexploded shells would be a real hazard, so this area is best avoided.
You could also approach from the minor road from Brough to Teesdale, above the Selset reservoir. The terrain north of this road (seen without snow cover) looks like very good nordic ski country, though perhaps rather heathery, with some splendid views over Brough to more distant hills like Wild Boar Fell. The provisos concerning the Army's Warcop training area apply equally to this approach, however. The road is also pretty vulnerable to snow (as you would expect from an approach that provides a high starting point), and has steep bits on the Brough side, though might be better from Teesdale.
The Tees - Lune watershed, with access on the north side at 240m on the Pennine Way south out of Middleton has some potential with a low snow line. Unfortunately, the logical summit of this ridge is Mickle Fell and the turning back point to avoid Warcop is in a rather unsatisfactory random place along the way: the highest point of Long Crag at 686m is about half a kilometre inside the danger area.
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