I do a lot of Winter backpacking. I've used a goretex military bivy several times right on the snow. A little story in regards.
Last year my brother in law came on a trip with me, and my girlfriend at the time. Hes a workhorse, and well experienced in the outdoors. He used the goretex bivy on this trip because we had planned on camping in backcountry cabins. This particular cabin had been condemned recently so we kept going. We ended up making camp about a mile off the ridge, trying to get out of some weather. Knowing they were calling for about 8" of snow in the valley, we figured up on the ridge would be a blizzard. Well, I woke up at about 2am to exactly that, a blizzard. Our tent was caving in from the snow so I had to get out and push the snow off the edges of the tent. It had dumped almost three feet of snow so far, way more then we had ever expected. I knew the general area he setup the bivy, but we setup camp in the dark while it was snowing, so I never got a good visual of the campsites surrounding. Never found where he setup cause he was 4 feet under a snow drift. He had setup the bivy in between two huge rock formations thinking they might keep the drift off him, but instead the wind blew all the snow right into that crack. I stayed up the rest of the morning, and I finally see him pop up out of the snow. He said he had one of the best nights of sleep hes ever had. Said he was overly warm. Said he woke up once over the night, and felt the heavy snow on him. He said it was almost like a gentle hug. He fell right back to sleep till the sun came up. Just happy as a pig in shit. My gf on the other hand, in a roomy tent, plush pad, warm sleeping pad was fighting back tears thinking we weren't gonna make it out alive.
I use mostly a bivy / tarp setup if I'm solo, and I feel pretty confident with it in most weather.
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