Beginning from the Bear Lake trailhead, you may need snowshoes immediately, or you may carry them to put on later. The trail goes steadily upward through conifer forest, likely to be cloaked in winter wonder. Broad switchbacks lead up the mountainside, and the snow is likely to get deeper and softer as you go. Eventually the trail breaks above treeline, into the alpine zone where conditions are highly variable. Depending on snow depth and firmness, you may stay in snowshoes or find it more useful to switch to shoe traction. Either way, you’ll continue upward at the mercy of the alpine sun and wind. Be sure to bring ample layers of clothing and sun protection.

The steepest part is the few hundred feet above the treeline. There, the trail zigzags through talus, and reaches the edge of the ridge overlooking Emerald Lake. Hallett Peak is clearly visible, looming above. The designated path may or may not be traceable through the snow. Just keep a close eye for the path of least resistance among the rocks and drifts.

Eventually the gradient mellows, but remains steadily uphill, on the shoulder of Flattop Mountain. This mountain has no pronounced summit, but a large cairn marks the highpoint. On Flattop you’ll be standing on the Continental Divide, and this makes a perfectly good turnaround point. You’ll see the jagged summit of Hallett within reach, however, and the ultimate view awaits on top. If conditions permit, simply continue along the broad ridgeline and up the final stretch to Hallett. Just beware of cornices near the edge which may be unstable. On top of Hallett you’ll look over the cliff-lined basin of Emerald Lake, and across at the route you just climbed on Flattop.

Source: https://www.nps.gov/romo/planyourvisit/upload/Bear-Lake-Winter-Trail-Guide-2017-digital.pdf