This is one of my favourite Welsh winter climbs. When it's in condition it's definately worth checking out.
Climb into Cwm Cneifon
From the car park by the west shore of LLyn Ogwen on the A5 follow the trail that leads south to Llyn Idwal and follow its east bank. Climb into Cwm Cneifion (The Nameless Cwm) which is the left of the two Cwms to the south. Right Hand Y Gully is located on Clogwyn Du at the top of the Cwm on the right (western) side. Look for the distinctive gully towards the right hand side of the buttress. This is the left hand gully (IV,4). Right hand gully is to the right of this. The main gully section starts higher up so the start is not as visible as the prominent Left gully.
The route is mixed from the large part with plenty of torquing and hooking. There's also a great hand jam manveovre on the first pitch.
1) Follow the narrow gully and climb a steep section. This is possibly the crux pitch.
2) Bear right and continue up a well defined gully with a thin layer in ice to a belay spot to the right before the second steep section.
3) The third pitch begins with a steep climb before becoming easier. A harder route is possible by bearing right initially on the pitch. This route I'd rate as a IV.
Cwm Cneifon from Llyn Idwal
Rope (preferrably double rope)
Pegs (I didn't need to use any however)
Leave the ice screws as this is strictly a mixed route!