SierraNevada, thank you for the fantastically knowledgeable, well-reasoned, and on-point response! I really appreciated understanding your logic and theory in arriving at an answer to my question and your accounting for the particulars of the situation here. Given little difference between water levels at 4am vs 6am, I think I'll probably depart from WP closer to 6am than 4am in order to take advantage of the daylight. Of course, that means slightly warmer temps and softer snow near the end of my approach to Icerberg Lake, but life is full of trade-offs.
