neckervd

There will be NO Glacier Express in the first half of December.
Therefore (and because Jamie is interested in the Bernina Express) I suggested to travel via Rhone Valley - Divedro Valley - Ossola Valley - Lake Mergozzo - Lake Maggiore - Milan - Lake Como - Valtellina Valley to Tirano and then via Bernina to Pontresina. The train change at Milan is really easy (no crowds of crazy foreign tourists in early December and plenty of time).
Other possibility:
Montreux dp 8.36 - Pontresina ar 16.56 (almost all by daylight) via Domodossola - Centovalli - Locarno - Bellinzona - Thusis.

PalenQ

Montreux dp 8.36 - Pontresina ar 16.56 (almost all by daylight) via Domodossola - Centovalli - Locarno - Bellinzona - Thusis.>

This is a nice option - ride the Centovalli scenic rail way which goes thru 100 valleys if the name is correct - not dramatic Alpine scenery but really sweet - Swiss Pass covers the whole route from Domodossola to Locarno even though much of it is in Italy - Locarno has frequent trains to Lugano - stay there and take the Majola Pass scenic bus (if running at that time of year) to St Moritz/Pontresina.

neckervd

In the first half of December the Palm Express buses run only Saturday, Sunday and Monday :
Montreux dp 6.35 - Domo 8.12/8.25 - Locarno 10.19/10.34 - Giubiasc 10.57/11.06 - Lugano 11.33/11.55 - St. Moritz ar 15.35.
That would be way too much for one single day. Leave Montreux 2 hrs later and sleep at Lugano.

PalenQ

Lugano is a really nice city and at that time of year I think rather warm compared to north of the Alps - it's only a few miles from Italy.

Great day Montreux to Lugano via the sweet Centovalli scneic railway - then Maloja Pass Bus to St Moritz/Pontresina.

PalenQ

https://www.google.com/search?q=cent...=1600&bih=1075

The Centovalli Railway in Pictures - one of the less heralded of Switzerland's iconic scenic railways (even though it goes largely thru Italy it's a Swiss train I think) = and a great way to go from the Brig/Domodossola area to Lugano and onto St Moritz.