This approach description assumes you are coming from the major trailhead at Lake Sabrina, west of Bishop. The route can also be done from the vicinity of Big Pete Meadow/LeConte Canyon in Kings Canyon NP.
Follow the Sabrina basin trail from the dam at Lake Sabrina (9,128') and follow it to Blue Lake. At Blue Lake, keep heading south towards Baboon Lakes. The trail can be difficult to follow through here, and kind of disappears 400 feet below Baboon Lakes. Just keep aiming up to the obvious bench that holds the lakes. Skirt the Baboon Lakes on the east side and follow the inlet stream up towards Sunset Lake. If you are camping, Baboon and Sunset Lakes are nice spots. If you are not camping at Sunset Lake, then do not follow the stream up to the lake. Instead, follow the right hand fork of this stream when it branches just above Baboon Lakes and follow it up to the saddle NW of Sunset Lake (between Peak 12,486' and unnamed point 11,680'+).
Contour above the NW shore of Sunset Lake and aim for the snowfield on the other side of the lake. The route should be obvious from here up to the Thompson Glacier. Once at the moraine, you will see Thompson on the left and Point Powell on the right. In between are two broad chutes, and a very steep and long couloir on the right. The couloir is the NE couloir of Point Powell and leads to the summit plateau of that peak. The middle (higher) chute is the Thompson-Powell Col. This photo paints a good picture of where you need to go. You'll be lucky if you are here in the early season when snow reaches to the top. Otherwise, the top part of the route to the col is filled with nasty scree and loose rock.
From the Thompson-Powell Col, your goal is to wrap around the backside of the prominent rock buttress that separates the Col from the NE Couloir of Point Powell, and then climb up to the broad summit plateau. Head to climber's right from the col, descending slightly where necessary, and aim for an obvious chute leading up to the summit plateau. The plateau forms a big triangle with Point Powell, Point Wesley and unnamed Peak 13,200'+ on the corners. Either peak is easily bagged from here. For Point Powell, head climbers right to the flattish summit ridge. Some small class 3 blocks guard the summit, but are easily climbed. The views from the summit plateau (and the summit proper) are outstanding.
Ice axe and crampons are nice for the steep ascent to the glacier and up Thompson Powell Col. The chute leading to the summit plateaud generally melts out early, but may still have snow as well.
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