30* quilt for April NoBo start on AT. Doable or just stupid?

I think you're fine. You could be a little cold if a cold snap came through, but I think you'll be fine. The average low on Clingman's Dome in April is 34 degrees. http://www.hikinginthesmokys.com/weather.htm Of course it can get colder but I would expect Clingman's Dome to be about as cold as you'll see. I think I'd take to 30 degree quilt with your extras. But I might be stupid.

I agree, it should be fine. Remember, if it's colder than you expected, you can always buy a summer sleeping bag or something on the way to boost your sleep system. Lots of EMS, REI, and mom-and-pop outfitters up here.

Alternatively

If you get really cold by the Western Massachusetts leg over Mt. Greylock, get in touch with me and I'll come bring you a warmer bag. I've got a ~3lb 20º Synthetic you can freakin' keep!

like others have said, you should be fine. Having a warm pad under you like the xtherm goes a long way. I use my 40 degree quilt in CO with an xtherm for about 5 months a year and I'm fine. You could probably leave behind the extra weight of the mylar and slippers too, but you're call.

enjoy the trail!

During a normal spring you will be completely fine. Last winter & spring were colder than normal, but the 2-3 years before that were extremely mild. So mild that several thru's decided to start in February last year. They were met with two feet of snow in the Smokies and 10deg weather. It's a crap shoot.

I would take the 30deg bag and wear the extra layers if needed. Besides, you will be ~5 deg warmer in the tent which will help.

Ryan

I started early April a few years ago and didn't have a single night below freezing for the first month. And only a couple the whole trip.
Also, in the south you can totally get ahold of different gear if you need to, so you'd probably only risk discomfort for a few days.
Honestly, if I was buying new gear for the AT that RevX 30 is totally what I'd buy.

Cannot speak directly to the conditions, etc, of the place at those times, but i've found that i can easily extend my sleep system down to 15 degrees below the rating of my quilt(s).

On my last trip, the forecasted low was 23 f. I used a 40 degree quilt and was fine. Some caveats. I used a polycryo VBL shirt below my down jacket (Stoic Hadron Anorak), and i also wore down pants.

Oh and i added an M50 fabric sleeve to the quilt which really helps to cut down on convective heat loss. (for about 2 oz weight increase, highly recommended!).

Probably really important to add…

I was in a somewhat closed up double walled tent with an IR reflective liner on the inside on that trip mentioned above. Might have made a bit of a difference too!

But, it was not as closed up as i wanted it to be, so there was plenty of venting and air convection going on.

(for those interested my tent was a 1.2 Mil polycryo 7X10 "tarp" with SOL heetsheets taped to most of the inside, it looks REALLY cool inside with a candle!)

I also think this is a totally reasonable decision. I did the same for the JMT and had a few nights that were into the low 20s and found eating a candy bar before going to sleep (or when you wake up at 1am freezing) really helped to warm you up when things were a bit tough. have fun.

Slightly different scenario, but I did the PCT with an April start and a 40 degree quilt … I ran out of money and decided to roll the dice.

Despite a low snow year, I had snow at both borders because that is how my life generally turns out. With all my clothing I wound up being fine, but I accidentally stumbled onto the positive attributes of VBL when in real need of extra warmth. At first I wrapped myself in my polycryo groundsheet, which actually worked very well in a pinch, but later I acquired silnylon raingear with waterproof front and pit zips (Lukes Ultralight) and it became my "oh crap" sleepwear, plus raingear, plus windshirt, plus bug proof temple. Funny how you can fall in love with such a simple piece of gear. I actually used that same system back down the GDMBR through October and into November. I was cold but I survived.

Best luck.

(EDIT: Just saw that Justin mentioned VBL above so … uh … basically +1 to what he said.)