Squaw Creek in combination with the North Ridge is the shortest approach available in winter without setting foot in the Squaw Valley ski area. A 2.8mi Shirley Canyon Trail runs from Olympic Village to the lowpoint on the Sierra crest between Tinker Knob and Granite Chief. In winter this trail is not marked and rarely followed directly. The lowpoint at the crest is a broad, tree-covered saddle, difficult to distinguish.
With snow cover, it is often hard to find the start of the trail in Olympic Village. While some say to look behind the Fire Station, there seems to be even more over-snow traffic at the far west end of the village, just north of the creek.* Lots of folks wander up Squaw Creek in winter and boot/snowshoe prints usually abound. Most folks seem to go upstream less than a mile before turning around. They also seem to wander about, leaving a multi-threaded path to follow. Pick whatever looks the most travelled and go with it. If you find snowmobile tracks, even better. Snowmobilers often use Squaw Creek to access the OSV area north of the Granite Chief Wilderness, and their tracks make progress on fresh snow far faster than without.
Follow the general direction of the creek upstream, staying north and high above the creek on good benches. Following the creek directly is a mostly miserable affair due to the steep ravine in its vicinity. The only possible difficulty is encountered at the steep slopes approximately 2mi from the TH. Watch for possible avalanche danger here and pick one of several lines leading diagonally up through the cliff band. Above the cliff band you can continue west to the saddle to the start of the North Ridge, or start angling towards Granite Chief earlier and intersect the ridge higher up. Do be cautious concerning skiers in the Shirley Lake area if you are encroaching upon the ski area boundary during operating hours.
For those that are of the opinion that because Squaw Valley lies within a National Forest, free access to all is a public right, consider that like most ski areas, Squaw Valley operates under a special permit. A primary responsibility of the ski area is for the safety of those that ski there. Removing persons deemed hazardous to the safety of skiers is within their right and part of their responsibilities, just like avalanche control. Just because you didn't get booted the last time, doesn't mean you won't the next. In general, if you stay in the trees and/or to the side of the ski area, you will probably not be hassled. Don't just start walking up the middle of a ski run like you own the place - because you don't.
adds: i've also heard that the trailhead is "behind the fire station". The easiest way I have found to the Shirley Canyon trail is to drive past the fire station and into the parking lot behind the random old run down looking lodge (I think it is called the Olympic Valley Lodge). Right behind it there is a fire lane with lots of no parking signs, and you'll see the trail leave right from the edge of the asphalt of the parking lot. There is tons of parking there in summer, as it is the squaw valley employee lot and is usually quite empty.
The North Ridge itself is 1.5mi long, with several intermediate highpoints along the way (pt. 8436ft & pt. 8615ft) that can be skirted on the left or right. Depending on snow conditions, the North Ridge can be a straightforward hike, an avalanche zone, or a steep, icy climb. The northern exposure often means that powder conditions last longer here than on other slopes, and when icy conditions develop it takes a lot of sunshine to soften it up. Consider recent weather conditions before deciding what gear to take with you.
The steepest section is just before the summit. If conditions make a direct approach untenable, you may be able to traverse right to the west side and climb the gentler slope found on that side.
Skis or snowshoes needed in winter. Consider bringing crampons and axe if icy conditions are a possibility.
If you have information about this route that doesn't pertain to any of the other sections, please add it here.