From Third Lake (see "Getting There" in main peak description) the North Couloir is the obvious gully to the right of the massive North Buttress. Find your way around the east end of the lake and head straight for the gully. The approach is a mixture of talus, scree and snow, depending on the time of year and amount of snowfall the previous winter.
The route becomes more interesting as you reach the top of the snow-covered debris cone beneath the gully proper. When I climbed this route in 1978 the snow field was much larger, and sported a modest Bergschrund near the top. The gully steepens significantly and narrows into a chimney here (Class 4-5, depending on conditions).
In 1978, this provided an enjoyable pitch of mixed rock and water ice (Class 5 under those conditions), and it still might, as the chimney probably never gets sun, and has an ample supply of meltwater from above.
Above the chimney the angle lays back. Follow the third class gully a few hundred feet until reaching some shallow gullies on the left. Choose the one that seems most appealing, and wander up towards the summit, climbing either in the chute or on the rokcs nearby. A third-class line can be found through clever route finding.
Descend the normal route by heading east to Contact Pass, and thence down to the North Fork basin. The descent involves either one rappel, or a short stretch of fourth class downclimbing. Do not take follow any of the large gullies angling towards the South Fork basin! You will not be able to get down without at least one rappel, and considerable extra effort finding your way back up to Contact Pass.
Unless your party is extremely confident on rock, a rope and a handful of rock pro is advisable. If undertaken when there is a significant amount of snow above the chimney, and ice axe and crampons are also advisable. There is plenty of protection in the rock along the gully, so specialized snow protection is not necessary.
No matter when you climb this route, BRING A HELMET. Everything that falls in a huge swath of the north face gets funnelled down this route (where did you think that big talus fan came from, anyway?). The area just above the chimney is the worst. Get an early start, and be well above the chimney before things get warm. We narrowly escaped being taken out by a rock the size of a VW due to being too slow on the route.
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