I went into the High Sierra in July 2008 right as the storms that wiped out the Mt. Whitney Fish Hatchery and closed 395 hit.
I had a small, one man tarp, down bag, and ditched a heavier GTX Paclite storm jacket for a Driducks top and a trash bag skirt to "save weight" because it was "summer".
Ended up fleeing from just above Vidette Meadow to over Forester (in a sleet/mild electrical storm), up Trail Crest (in a hailstorm, though it cleared by the top) and down to the portal in a day. Why? I tried to hunker down but winds and driven rain were so strong that my bag, bivy, and all insulation were soaked completely within 3 hours. I figured if I didn't run out, I'd freeze or get killed by a blowdown or lightning; moving was the only way I could keep warm. I'd say it ended up a good gamble; the storms kept up for a few more days- there would've been no drying my gear.
No more 5.5 pound baseweights at 12000+ feet for me unless it's a dayhike or run.