Another member asked the question of how you navigate above treeline in a whiteout (blowing snow & fog)?
As a disclaimer I should say that being above treeline in a whiteout is not the preferred condition for climbing. It is dangerous and generally not very fun. Although, it does happen and if you are doing a Presidential Traverse its hard to avoid.
My first piece of advice is to not lose the trail. Theoretically you can navigate from cairn to cairn in the worst summer fog, so you should be able to do it in winter. Having two people in this situation is very helpful as one person can stay at a marker while the other goes searching for the next one. Blowing snow obviously complicates the matter and rime covering the next cairn can make it even harder to spot.
Most people would say, "Use a compass, duh!" Easier said than done. Following a bearing in a whiteout with the wind pushing and no reference points is not easy. Using a compass is a viable technique, but it takes practice and you need to know where you are going. Chauvin Guides has an excellent whiteout navigation plan in their guide to doing a Presidential Traverse on their website. You could always design the same whiteout navigation plan for a climb up Lion's Head, just be sure to adjust your declination properly.
This is where GPS really comes in handy. You need to be an expert at using one, even with thick gloves on and frosted over goggles. You also have to be prepared if the GPS fails. Before you leave for your trip program the GPS with several waypoints. If you lose the trail you can then use the GPS to travel from waypoint to waypoint. You probably don't want to have the GPS on for the entire hike so once you get to a waypoint I would use a compass as the primary source for navigation, then as you get closer use the GPS to hone in on the next waypoint. Again, this is a serious reliance on a your GPS so there is risk here.