This is one of the best ski lines in the White Mountains, and possibly the most aesthetic. From the parking lot in Pinkham Notch. This skinny couloir evokes inspiration and fear. Upon first look, you either instantly want to ski it, or are certain you don’t. This would be the most popular line in the range if not for that pesky Harvard Bulge. A 60 foot vertical ice bulge that seals off the bottom of the line, a fall or avalanche in Diagonal Gully could result in one being swept over the edge, with serious consequences. As a result, Diagonal is respected and feared. For the purposes of climbing and skiing the line, it is possible to climb the entry to Yale Gully, and climb a thin snow chimney to climbers right of the Harvard Bulge, so you can leave those ropes and ice screws at home. Top out the gully at a small snow patch just below the junction of the Huntington Ravine Trail and Alpine Garden Trail. Put skis on here and drop in. A steep convexity presents the first crux, as you drop into the high walled couloir. Consistently steep and memorable turns take you down Diagonal, with the constant awareness of the big exposure as a reminder to keep your slough beneath you. A number of safe zones are available to pull into, so you can ski the route in sections. As the walls open up, side slip to skiers left, getting uncomfortably close to the Harvard Bulge, until you can get into the skinny ribbon of snow. Side step down into the exit of Yale Gully and ski out to the fan.