|Flattop Mountain - N side
Flattop Gully is a nice snow climb on the north side of Flattop Mountain. The couloir is tight and curvy so that you can't see very far ahead of you. This gives it a fun maze-like quality. I'd guess it's mostly about 45 degrees, but at the very top it might approach 60 degrees. Depending on snow conditions there might be a couple of short rock steps in the middle but these are easily scrambled over.
For the easiest climbing, angle toward climbers left at the first fork and then bare to climbers right above that. Angling toward climbers right at the first fork may get you into some more interesting mixed climbing and eventually you'll be forced to climbers left.
I shot this video of an ascent on 5/20/06: video.google.com/videoplay?docid=-1034977532508729600
To get there, hike above Lake Helene to the tarn below Notchtop Mountain. From the tarn, I advise ascending the snow field on climber's right (closer to the Notchtop side) so that you can get a good view of Flattop Gully. If you hug the Flattop side, you won't be able to see the route very well or the branch options.
You can't miss the start of the route.
The couloir tops out right at the summit of Flattop Mountain. You can then either hike back to your car down the Flattop trail or glissade the Ptarmigan Snow Fields and hike back the way you came.
Under ideal conditions no protection is necessary. If you're not comfortable on steep snow then maybe a couple of snow pickets and a rope would be nice. The route is mostly about 45 degrees but possibly approaches 60 degrees at the very top for 50' or so.