I just had my first experience bivying in a storm and it was only semi-successful. To keep condensation at a minimum I tried propping my jacket over the head with ski poles so I could keep the zipper unzipped mostly but ended up getting a nice amount of spindrift to the face every so often. I also was pretty frustrated just trying to get into the bag without letting in a whole bunch of spindrift.

Anyone have anything to relate as to tips to bivying in inclement weather?

I camped out on top of a 2200m high mountain over the weekend in my Jack Wolfskin Gossamer tent - which is basically a bivy with two poles. Got completely snowed in to the extent that the tent collapsed on top of me. Since I have a really good sleeping bag and was too lazy to act upon it, I decided to ignore the problem and go to sleep. I woke up in the morning (still toasty warm) and found out that there was about 1m of snow on top of me. Bad stuff.

My best advice would be to dig yourself slightly in and to place a tarp over the hole. Basically, you are making a coffin with a tarp on top. I did that before and from now on, will either leave the tent and use that tried and tested technique or I will get a better tent.

I have never successfully stayed warm and dry in a storm in a bivy sack.

A bivy sack may keep you alive, but not warm and dry. In order to stay out over successive nights in a storm, you need a tent.

Period.