The mornings and nights during your week-long climbing trip to Vedauwoo can be chilly when you aren't sending it. Throw on the Arc'teryx Men's Nuclei Hooded Insulated Jacket to maximize your warmth without being weighed down. The Aieretica lining and face fabric is tightly constructed and highly tenacious, which means it can take the abrasion of the sharp Vedauwoo rock if you brush up against it.
The Nuclie is stuffed with Coreloft insulation, which is made with highly crimped multi-denier siliconized polyester yarn, so, basically, it is lightweight and breathable, compressible and has an excellent loft retention. You can put the Nuclie in the interior stow pocket when not in use, and you can also use the clip-in point for attaching it to a harness.
Trekking, climbing, snowshoeing and cross-country skiing build up a lot of core body heat where the Nuclei has the most insulation, in the torso area. This is the reason the Nuclei warmer and is lighter than the Atom LT. If you are wearing a good shell jacket over the Nuclei or the Atom LT, use the pit zips to dump heat when you need to.
IMHO the Atom LT and the Nuclei are both great mid-layer and stand alone jackets for similar conditions. The Nuclei would be better with a drawstring hood like the Atom SV.
The Nuclei and the Atom LT have proven to me over and over they are great jackets for any active Fall to Spring pursuits. They are cut similarly and offer space for layering, the Nuclei offering just a little more. I wear an Ibex heavyweight woolly and a mid-weight Patagonia base-layer with either jacket and a shell if the weather calls for it and there is still room to spare if you want more insulation. The shoulder to arm articulation (angel-wing cut) and longer sleeve-length is great in reaching as you ski or climb or trek or in base camp because your wrists and midsection remain covered and heat is kept in; also the wrists closures on the Nuclei jacket are not as tight as those on the Atom LT and Atom SV. However if you trek or hike in weather that's equally snowy and rainy or more rainy you might like the Atom LT a little better as the front edge of the Nuclei hood is shaped to cover more of the face and is a little more exposed to the rain. Lessons learned. Overall the Nuclei and the Atom LT are both Great Lightweight Jackets! I've given the Nuclei five stars despite the shortcomings because it is so well made and the company is dedicated. I just really like what great gear does, a lot!
The Nuclei is very warm, well, even without taking into account the weight, or lack of it. Packs into a very small bundle, cuffs fit well, though not quite as good as the Atom LT. Sizing, for me, is a bit on the small side, especially across the chest. I was a little surprised at that. I had hoped that it would be a bit of a looser fit than the Atom LT. Especially as I was wanting to use (the Nuclei) as a minimalist belay jacket-however, that is not a deal-breaker, by any means. The best part is the warmth of this thing, flat amazing for the weight. That is enough to earn my respect.
Very warm - comfortable by itself to the 30s, and that with a wind. Sheds light precipitation. Packs to nothing into a tiny stuffsack. Layers smoothly. Well constructed hood (non helmet compatible - a plus for me - yet bigger than "scuba" with excellent visibility and coverage). Arm length and cuffs are spot on. Then as a bonus, looks very sharp as well - have worn the heron color proudly around town and to my executive meetings over a button-up shirt. And all for 10 ounces? (That's what my hoodless, gridded, non-wind blocking ultralight fleeces have weighed). Perfect!