In reply to alex.murray:
With that time frame you won't be able to acclimatise much, but you could do a short trek and maybe climb a 5000+m hill.
Langtang valley is probably the best bet, as you can be up high in the valley a few days out of KTM and maybe trek up Tsergo Ri and nearby hills, snow permitting. There are also waterfalls that freeze on the southern side of the valley (facing north) and some have been climbed. You'd need to check it had been cold enough before lugging technical gear up there though. Since the 2015 earthquake devastated the villages, they have been rebuilt, and also the track has been re-done. For a year or so there was a new track on the other side of the valley, with fewer lodges, but I believe now (when I checked in KTM in Nov) that the old route is mostly restored.
You can also get high into the Manang valley (north side of Annapurna massif) now in two days from Pokhara, via bus and jeep, so that is also an option. If there wasn't much snow you could even do the Circuit, over the Thorung La to Jomsom and fly or bus back to Pokhara. There's probably less of a chance to top out on a small hill in Manang, but there are more lodges and bigger scenery.