I have had so many beautiful weather days climbing in the Cascades – sunny days where you can see all the way from Mt. Rainier to Mt. Baker are my favorite. I’ve also had plenty of terrible weather days in the Cascades, with rain freezing sideways onto my ice axe. It’s hard to find a jacket that can be brought on both types of trips, but the Arc’teryx Nuclei FL fits that role.

Arc’teryx Nuclei FL Jacket Features:

  • Coreloft™ synthetic insulation provides warmth with minimal weight and bulk
  • Articulated patterning for unrestricted mobility
  • Gusseted underarms for mobility and comfort
  • Helmet compatible StormHood
  • Adjustable hood drawcord with single pull adjuster
  • Full front zip with wind flap
  • Adjustable harness compatible hem
  • Two hand pockets with zippers
  • Two internal dump pockets
  • Utility loop for easy, secure storage
  • Claimed weight: 11.5oz
  • MSRP: $299
Arc'teryx Nuclei FL Jacket Review

My face when it pours rain all day and the trail is snowed over. This is fun, right?

Big warmth in a tiny package

The Nuclei has been with me for a full summer of adventures, including some terribly wet and cold spring adventures, some really pleasant and warm summer climbs, and now again some wet fall adventures. What I’ve appreciated about the Nuclei FL is its versatility – it’s warm enough that it can cut it for the shoulder season adventures and its synthetic insulation shrugs off moisture. At the same time, it’s light enough that it can serve as my warm layer for summertime glacier travel when I might just need it at dusk or dawn when I’m out of the sleeping bag.

The profile of the jacket is pretty simple. You’ve got two zippered handwarmer pockets and two big dump pockets inside, which is great for stashing bars, gloves or whatever when you’re on belay. Otherwise there aren’t too many frills, except for an adjustable hem and Arc’teryx’s signature Halo hood. This fits a climbing helmet easily and has a single-pull adjustment. I like Arc’teryx’s hood design because it cinches nicely around your neck when it’s down, and when it’s up the single adjustment does a great job at keeping it in place and saving your peripheral vision.

Arc'teryx Nuclei FL Jacket Review

I love the Halo hood

The foundation of the jacket is the proprietary Arc’teryx Coreloft insulation at a weight of 65g/square meter. That’s a fairly light insulation weight. The active insulator Proton LT I tested in the spring had an 80 weight Coreloft. It points to the fact that that this is meant as a ‘fast and light’ piece – this isn’t meant to be a winter insulator for alpine pursuits.

It can be good in the shoulder season, especially on wet trips, when you’re in and out of the jacket or can easily dive into your cozy sleeping bag and tent when the temps really dip. For summer alpine climbing, I found it absolutely perfect – very light, and plenty warm. On the trips when it did get wet, including an epic springtime journey on the Loowit that circles Mt. St. Helens, I stayed warm when wet and it dried off quickly – just like you’d hope for from a synthetic.

Arc'teryx Nuclei FL Jacket Review

Love the nice tall collar when it’s zipped up

Layered over the Coreloft insulation is Arc’teryx Arato fabric in a 10D weight. This is essentially a 10D ripstop nylon, and it looks, feels and works like any other 10D nylon. The fabric weight is definitely another key point about this jacket: ultralight does not equate to being particularly durable. 10D fabric will hold up just fine, but it takes a little more care than heavier 20D or 30D fabrics. Bear this in mind if you’re scrambling around in rocky environments or don’t have your crampon points covered in your pack when you shove the coat back in there.

Speaking of shoving the coat in your pack, Arc’teryx chose to do a built-in stuff sack which I actually really like. It packs up plenty small and has a carabiner clip for easy access. Wearing this in a harness works fine, largely because the fit of the jacket is fairly billowy around the hem. There is a single hem adjustment which helps. I have to say, this is not a particularly sleek Arc’teryx jacket: the product page says slim fit but this is definitely built more like a belay jacket with room for layers beneath. Great for the outdoors, but might look a little baggy around town.

Arc'teryx Nuclei FL Jacket Review

The Nuclei is your friend for alpine starts

In practice, the jacket proved a perfect companion for the glacier climbing that I did this summer. The weight is just right for cool nights and cold mornings up on a glacier, especially when you have either a sleeping bag or hours of activity to look forward to to warm you up!

The one uncomfortable thing about the nylon fabric is that it feels very clammy if you’re sweaty at all. The insulation isn’t zoned, so I noticed this particularly in my forearms which are prone to feeling hot and clammy. In fairness, this isn’t meant to be an active insulator — but you’ll definitely notice it when you get sweaty in the jacket.

Arc'teryx Nuclei FL Jacket Review

Two big internal pockets and the built-in stuff sack are much appreciated

The Good

  • Really light and plenty warm for plenty of summer or shoulder season pursuits
  • All the zips, pulls and features work without issue
  • Big internal dump pockets are appreciated, as is the integrated stuff sack
  • I appreciate how small this packs down for summer or fall warmth
  • Arc’teryx’s Halo hood is one of the best

The Bad

  • Fit is very generous, erring towards voluminous
  • 10D fabric is light, but be mindful of abrasion

The Bottom Line: Arc’teryx Nuclei FL

This has been the perfect summer adventure buddy, and it has a lot to offer in the fall and spring, too. It’s great for those trips where the temps aren’t going to be too frigid or if there’s some precipitation in the forecast when you want a synthetic. It’s light enough that you hardly notice it in your pack or harness, which makes the Nuclei FL easy to love and easy to bring along.

Buy now: Available from Backcountry.com

About Author

Kevin Glover is an outdoorsman living, climbing and biking in Spokane, WA. Originally from the Nevada high desert, he moved to the PNW for its mild winters and allergen-free summers. He has guided throughout the Cascades and Enchantments for Peak 7 Adventures.

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