What sleeping system needed for Sierra hike nexst week

Pretty hard to tell how this will work for you without some further info. What temperatures have you experienced previously with that setup of quilt, pad and bivy?

The NeoAir Trekker is an R3 matt, if you believe Cascade Designs.

Depending on your resting metabolism, that may or may not be enough for 20°F.

If the forecast turns out to be optimistic you can always do 30 "crunches" every couple of hours ;-)

It's the first time I will have the snowyside bivy with the other gear.That should make a bit of difference. I have not been in temperatures this low with any gear. I've been in 30's and the pad was great.Headgear would be an addition. As you can tell I am not experienced with snow and cold backpacking. Heck I can always walk out. FIrst night I will only go in 5 miles :)
Clothing tips would b appreciated.Thanks for your responses

No you will not be comfortable. I needed more R underneath and more up top too. A good hat,gloves and puffy would make a big difference. You might not sleep well because of drafts but you'll be ok and have a decent story to tell.Nice up there this time of year.

Bivvy only, no tent/tarp?

I'm not as concerned about the temperatures as I am about the weather. I just checked the forecast for that area, and it says to expect increasing clouds starting Wednesday.

Be very careful heading into the Sierras as snow season begins, especially going for the first time and going solo. Think Donner Party. Be over-prepared. I have winter-camped in the Sierras for 30 years and skied the Winter Sierra High Route. I have been surprised by the weather more than once.

Personally, I wouldn't go to that location at this time of year without a 4-season tent that can support a snow load. If you're 5 miles in and it starts to come down, you may need to hunker down for days. You can't cook or melt snow in a bivvy. And the tent adds at least 5-10 degrees of warmth and will keep you drier.

Do you know how deep the snow cover is now? Will you be traveling on foot, snowshoes, XC skis? 5 miles can be a LONG distance in snow.

What trailhead are you hiking in from? Make sure the road to the trailhead is open and accessible.

I was gong out of Crabtree and heading to Gem lake. I say WAS as I am down with the flu this AM. After reading your posts I was rethinking the trip anyway. I talked to the rangers at Summit station(Pinecrest) and was going to check again today BUT these are VERY GOOD points. I will try again with someone experienced. It would be nice to be in the snow. You NorCal guys who have done it and have time to share your experiences or can direct me to such firsthand info, it would be greatly appreciated :)
Again thanks BPL responding members :)

Glad you are reconsidering. Winter is not the time to go alone, test new gear, or take chances. Hopefully next time you will have someone with winter experience along and have tried/tested gear up to the possible lows.