The Rockies in winter are known for their cold temperatures and fierce winds. When I’m climbing ice in these mountains I need a belay parka that blocks the wind, has enough loft to keep me warm at a long belay, and compresses enough to carry easily on the back of my harness.
Reviewed by: Drew Thayer, Senior Contributor
Arc’teryx designed the Nuclei AR jacket to perform in wild mountain weather. This jacket wraps 100 gram Coreloft synthetic insulation in a Windstopper shell that’s water-resistant and wind-proof. The idea is a jacket that’s warm enough and resistant to the elements, using neither down nor a waterproof membrane like GoreTex or eVent. Let’s see how it performs.
Resilient, compressible synthetic insulation:
Down insulation certainly has the best warmth-to-weight ratio, but is useless when wet. Down parkas can work great in dry winter cold, but spring conditions, rain-showers, or even the drips from a crevasse lip or iceflow can render a down jacket’s loft into gloppy wet lumps. For years down was the only serious choice for compressible jackets, but synthetic insulation these days has improved. Despite its warm loft, the Nuclei AR jacket stuffs into a small stuff sack 9 by 4 inches long and hangs unobtrusively off the back of my harness.
Medium weight: This jacket weighs 15.9 oz at size medium. That’s a couple ounces heavier than light synthetic parkas like the Patagonia Nano Air (13.6 oz) or Rab Xenon (14 oz), with much more warmth and weather protection. This jacket is still on the light side for winter parkas, and probably isn’t adequate for long static belays in single-digit temps. A full-on down parka like the Outdoor Research Virtuoso (1 lb 7.3 oz) feels like wearing a sleeping bag on my upper body, weighs 46% heavier, and takes up much more room on a harness or in a pack.
Fit and design: Overall, this jacket is intelligently designed for climbing and skiing. I appreciate the low-cut butt that guarantees I won’t get a cold ‘plummer shock’ when I bend over to adjust boot buckles or crampons. Lofty hoods on some parkas can remain pretty rigid, blocking my vision when I turn my head. The adjustable hood on the Nuclei AR turns with my head while sealing out wind, and works equally well with or without a helmet. The wrists lack the ultimate security of Velcro closure, but the tight elastic cuffs are adequate for sealing out wind and spindrift. Two external pockets sit above a harness, and an internal mesh pocket is handy for keeping an extra set of gloves warm. My only complaint is the minimalist zipper, which tends to catch at the bottom and can require some fine dexterity to engage. I’d rather Arc’teryx added a quarter ounce of weight and used a burlier zipper.
Weather-proof: I have yet to see this jacket get wet. Leaning against wet ice, getting dripped on at soggy belays, even skiing 7 hours in a wet blizzard in Flagstaff—the Windstopper coating does a great job repelling moisture. This jacket will protect from the elements in all conditions short of real rain.
Bottom Line: This jacket is an ideal belay parka for skiing or winter climbing down to teens temperatures, with enough warmth for long belays and total protection against wind. At temps into single digits a down parka with more loft might be necessary for most folks. The Windstopper fabric will protect against all but a downpour, and the synthetic insulation remains warm when wet anyway. It’s Arc’teryx, so it’s quite expensive, and you get what you pay for: the build quality is superb. I’ll trust this jacket to keep me warm on ice climbs in Rocky Mountain, ski descents in the San Juans, or mountaineering routes in the Coast Range.
Arc’teryx Nuclei AR Jacket (on backcountry.com)
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