I know how you feel. Back in the day, I was unique in having parents in their 30s when I was born. My husband's parents were about 40 when he was adopted. Today's kids have parents who, very often, were well into their 30s or early 40s when they were born. So more and more of us will be relatively young when we bury our parents. Contrast this with people like my mother who had all 4 grandparents alive when she was well into her 30s and beyond - so she "practiced" as an adult with the deaths of her grandparents long before she had to deal with her parents' deaths. That's not the same now for many families.
You're on the right track by facing tho snow. And your parents are fabulously realistic by getting so many of their ducks in a row long before exit's necessary. This is a huge blessing for you!
My advice is to be sure you know where all these papers are - life insurance policies, continuing care policies, info on pensions and investments, and so on. You need to know the name/number of their attorney, their tax accountant, etc.
You also need to have a health care proxy for each of them even if they are the other's primary proxy. You need to know their wishes regarding extraordinary measurers and end of life care. (In fact, much as you don't want to thing about it, you and your husband should have these for each other. A colleague of mine did not have this, her husband had a stroke and couldn't speak, and she had to take time off from being with him in the hospital and planning his rehab to pay $3000 to a lawyer (with her adult kids at her side) to get a court order so she could make medical decisions. It was awful. If only, she thought, we had done this for free with the primary care physician. But no, her stubborn husband refused to address it.
If you have siblings, be sure everyone is on board and informed - this should be a family meeting with them and your parents (not necessarily with your spouses. If you can't all get together, do something by Skype. If you don't all get along, have your parents write a letter to all the kids in their own words and expressing their wishes. This takes away a lot of the arguing if things are contentious, but even if they are cordial, it takes away a lot of the worry and decision-making angst if it's already decided. A lot of the "how do I prepare" stress comes from not knowing how to handle the many details and decisions. If that's all spelled out and understood ahead of time, you and your husband and your siblings/spouses can be on the same page emotionally, and that is a HUGE comfort.
When I was growing up, this stuff was all talked about openly. When my great grandmother died when I was in high school, I was with my mother and her brother/wife/kids and their parents in the funeral director's office. I listened to them collaborate on the details for the obituary, the time/location of the funeral, the location of the cemetery, and so on. I watched them cooperate, laugh, cry, argue (over her date of birth - she used to lie to make herself older!), and so on. I saw it again when my grandparents died, and I was fully prepared for everything but the grief when my dad died. It was a huge help to my mother to have me with her in the funeral director's office, as she had been with her parents when Great Grandma died. Something as small as "How many copies of the death certificate do you think you will need?" is complicated if you don't know how many pensions and insurance policies there are. So being prepared is helpful.
Like anything else, you get good at it with practice. I hope that doesn't sound morbid.
My mother was near death in December. Although she pulled through, she doesn't have a lot of time left. I have made lists of things like what papers get the obit, where memorial observance will be held, where donations may be directed in lieu of flowers, who needs to be notified (sort of a triage list: whom will I call, whom will my husband call, which people am I designating to notify different groups (the community chorus members, the retirement home friends, the old neighbors from "back home" who will need to know, my neighbors/friends, any other "constituencies" including friends I'll beg to clean my house and coordinate some food), and so on. I know people who have collected photos or poems or old wedding announcements etc. for a display. Sometimes the older grandkids can be pressed into service making a video to be shown at the home or even on endless loop at the calling hours.
When all this stuff is done, you can focus on the grief. But it's also strangely comforting to look at your parents over the course of their lives - individually, as a couple "courting" and before kids, your early years and college years, your children's births and the new role as grandparents, and so on. It helps you see them as full and complete people, not just your parents, but much more. Knowing that you will see each of them as having "A life well lived" will actually center you and comfort you before the time of comfort is upon you. It may move you into more of an "adult" or "shifted" relationship with your parents - you aren't just their daughter, you are their future caretakers and decision-makers when the dynamic changes. You will do for them what they have done for you - step into the bigger role.
And as for moving - seeing you on your own in a new state with your husband and children may actually relieve your parents of the responsibility to "be there" for you every day. That may bring them some peace and calm, knowing that you are okay on your own. If they have to worry that you will not be okay, it's going to stress them out. Now's the time to think about all that they have given you and how they have prepared you for life without them.
Good luck - I know this is so hard. But you will be glad you went through the process and did some of the difficult things now.