In reply to Peterswindley:
Sorry to re-iterate, but it's probably worth repeating: As others have said, SAIS is running fine but full forecasts for Torridon don't start until later in the month. I've amended your thread title so no one is misled. Whether or not that service is running when you get there, you also need to be able to judge things for yourself.
At present there's no snow up here, but the weather is cooling down and conditions could change several times between now and when you come. By early December you could have anything from bare ground to full-on winter conditions; heavy snow and high avalanche risk definitely isn't unknown outside of the SAIS forecasting period.
It's worth mentioning that Spidean a' Choire Leith is one of the more challenging mainland Munro summits in winter conditions. In walking terms there is no easy way up or back down, and I've always felt like it's mountaineering. The standard path up onto the east end of the Liathach ridge from Glen Torridon is very steep at the top; it's high consequence ground in snow/ice, and potentially exposed to avalanche risk from crags overhead. Once up on the ridge, heading west it's easy scrambling in summer but snow cover gives it a real alpine edge and I think in full winter conditions you're basically doing grade I winter ridge traversing with lots of exposure in places. You'll be coming back down the same way too.
(Pictured here, the east ridge of Spidean a' Choire Leith - it's great, but depending on conditions I can imagine a lot of walkers finding it pretty scary)
In winter, pretty much any other single Munro summit in the area is less serious and technical via its easier routes. Does it have to be this particular summit? Forgive me making assumptions, but from the tone of your question I wonder if you'd be better off choosing something else? For example, Mullach An Rathain is considerably easier up and down from Glen Torridon, if you're fixed on doing a bit of Liathach. There are few crap hills around here, so you'll have a good day whatever you pick.