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Temperatures at higher elevations

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Re: Temperatures at higher elevations

Postby Wandering Daisy » Tue Aug 09, 2011 4:58 pm

The patio lunch I cited above is at Curry Village. Dennigans Deli near the Visitor's Center is also quite good. When you come into Yosemite at Tioga, they will give you a quartly flyer- it has good information on the places to eat and the stores. I think it also has a pretty good map.



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Re: Temperatures at higher elevations

Postby iHartMK » Tue Aug 09, 2011 8:37 pm

Just came out of Sequoia and Kings Canyon NP backcountry... never needed my jacket once. It was very warm up there.
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Re: Temperatures at higher elevations

Postby cahiker » Tue Aug 09, 2011 11:52 pm

I stayed in the Yosemite Valley BP camp one Friday night last August and had a pleasant drive in from 120. No traffic at all. I probably arrived around 7-ish. There is also parking along the road on the way from North Pines CG as you approach Curry Village, although it could be all taken. No bear boxes there, but presumably you'll have all your smell-ables with you in the bear box at the BP camp. Less than a 10 minute walk back to camp.

As others have said I'd take the Sierra weather forecasts with a grain of salt. I haven't had a night below 40 in the last couple of years but I've had a lot of unforecasted rain. I'm probably due for a cold snap on my trip next week...
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Re: Temperatures at higher elevations

Postby East Side Hiker » Wed Aug 10, 2011 8:38 am

We were at 8,300' last weekend, and didn't even need more than a comforter to keep us warm. Ah, California!
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Re: Temperatures at higher elevations

Postby amigo » Wed Aug 10, 2011 9:34 am

Sounding great. Thanks all for your inforomative feedback. Really appreciate it.
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Re: Temperatures at higher elevations

Postby Wandering Daisy » Fri Aug 12, 2011 9:29 am

I select the sleeping bag I take based on predicted night temperatures. I am leaving tomorrow for a week's trip to Sphinx Lakes and Brewer Creek and will be camping above timber at 11,000 feet elevation. NWS forecasts just at or a bit below freezing at that elevation. So I am taking my 10-degree bag since I only have a 45-degree and a 10-degree bag to choose from.

Oh the other hand, my clothing taken depends on daytime temperatures. There are big temperature swings at high altitude- I plan on being inside my bag as soon as shadows hit my campsite- so daytime clothes are geared to the 50's and for lots of wind. Right now I am trying to decide if to bring a down vest- not really needed but sure nice to have on cold mornings- we are going to climb so will be doing some crack-of-dawn mornings. I do have the option of staying in my sleeping bag and cooking breakfast in the vestibule of my tent. If you are the kind of person who likes to sit around in the evening and not go to bed early, a down vest or down sweater is really nice. You could however just wrap your sleeping bag around your shoulders.

I have found that the NWS predicted temperatures are pretty accurate. You can zoom in on their little map and click on the exact place you plan to camp. The temperatures are estimated using computer modeling based on elevation and terrain. When you zoom in, the NWS website now uses Google Maps so you even get contour lines! Also look at their "tabular forecast"- it gives you an hour-by-hour prediction of temp, wind, precip probability and other things. Again, it is all generated by computer modeling. It appears that you will be below 9000 feet and mostly camped in timber- in that case you will not likely have very cold night temperatures.
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Re: Temperatures at higher elevations

Postby markskor » Fri Aug 12, 2011 10:31 am

Spent more than a few nights at 1000 Island and have come to expect almost anything there. You could get lucky and it will be "balmy" - nightly lows in the 40º range, (in which case the bugs will probably eat you alive), or it could just as easily drop below freezing. Also, frequently high winds do arise there (which always totally messes up the great fishing). In short - hard to figure that place out beforehand, but always plan for the worse case scenario - just saying.
FWIW, was there 3 weeks ago and overnight temps always froze. Carrying a 15º bag (never zipped up at night) made sleep easy (hate being cold at night) and spent the entire days wearing shorts, with a good layer of fleece mornings and evenings.
Bring Deet!
Great trip and have fun.
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Re: Temperatures at higher elevations

Postby Shawn » Fri Aug 12, 2011 11:22 am

a week's trip to Sphinx Lakes and Brewer Creek and will be camping above timber at 11,000

Ah - one of my favorite places, hope you bring back photos. The first time I was up there, as a pure novice I really froze my backside off late in the season. Woke up in the middle of the night with everything on the interior side of the tent frozen. Last time I was up there, I slept like a baby in a properly rated sleeping bag out in the open (next to the upper most lakes).
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Re: Temperatures at higher elevations

Postby Hobbes » Fri Aug 12, 2011 12:41 pm

I don't know if any of you guys/gals are into utilizing CLO values, but I've found they're pretty useful for determining basic layering strategies - especially if you're playing around with UL limits.

For those who are unfamiliar with the process, there are models (developed by the military - 'natch) that project metabolic rates for different activities, ranging from sleeping, camp chores/light activities (eg fishing), to strenuous hiking.

Secondly, there are different CLO (thermal) values for various materials, including down, insulation, fiber, materials, etc. (The more reputable bag mfgs calculate their EN 13537 ratings based on CLO values, rather than just throwing some numbers out.) Again, almost all syn materials were developed for military use seeking max warmth/min weight + adverse conditions (read: wet).

So, simply by finding your own baseline comfort range, you can then add up the necessary layers required to keep you warm for different situations. Here's a quick example:

1. At what temperature are you comfortable if sleeping nude? 80, 75, 70? Note that this is the temperature where you would never be chilled or reach for a blanket - for the entire night.
2. Next, add in shorts/t-shirt for a CLO of .4; after than polypropylene LJs for .7. At this point, you've got a CLO of 1.1, which for many people will get them comfortably down to 65. (Again, no reaching for a blanket!)
3. Now we get to the bag. Based on EN, 1.2" of loft (for APEX) achieves a CLO of 4.1 or around 48-52 degrees. (This also coincidentally agrees with Jardine's (100-(40*L)) calculation.) If you add your 1.1 of clothing to the 4.1, you then get 5.2, which is good for around 40 degrees.
4. To get to freezing, you need to come up with another CLO of around 1.0. A down vest is good for 1.3, so that actually gets you to 30. Or, you could go with more insulation and forget the vest. By adding another .6" of loft, that buys you 6.1, or 32 degrees.
5. Add back the vest, and you should be able to get down to around 20-22 degrees without flirting with danger.

Note: all these calcs assume min wind and/or you're using either a bivy and/or tarp.

From a UL perspective, a synthetic (APEX) 30-32 degree/quilt with 1.8" loft weighs around 32 oz (2lbs). Since the LJs come in handy for base layering anyway, they are in essence 'free' add'l insulation. A 12 oz down vest comes in handy if you're hanging around + provides great insurance if temps drop below zero.

Add a tarp/bivy weight of 1lb (including guys/stakes) and a pad/ground cover of another 1lb, and you can see you have 4 lbs for 3 of the big 4. At this rate, a pack can come in under 1lb, so your big 4 comes in under 5 lbs. If you've got 4 lbs of clothing (including rain gear, hoody, gloves, etc) and 1 lb of the 10 essentials, you're now a UL BPer @ 10 lbs base weight. Voila.

Actually, my base is 9, so by adding in bear can+food/water/fuel+accessories, my std 20 degree min, 4-5 day pack is around 17-18lbs. Under 20lb, and a lot of BPers could carry this weight on their shoulders alone. If you add a sternum strap + waist belt + proper compression/load balancing, it feels like you've got nothing on at all.

That's how you can walk miles with your *head up*, looking around and enjoying the day.
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Re: Temperatures at higher elevations

Postby rlown » Fri Aug 12, 2011 1:07 pm

technically complete, Hobbes.. but.. it's easier to assume that a 15 degree bag is "good enough" for the Sierra (with or w/o a tent depending on pending conditions), and be done with it. For daytime stuff out of the bag, It really depends on the individual to pick his/her gear, if fishing, reading, cooking gourmet meals, or doing camera stuff. It's the "extras" that add the weight. I love the extras.. :)
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Re: Temperatures at higher elevations

Postby quentinc » Fri Aug 12, 2011 8:51 pm

Hobbes, I think I'd overheat just trying to do that computation. :)

At this point, I just have a 15 degree bag -- it's a Marmot Helium and it's so light I can't see any possible need to get a 30 or 45 degree bag too just to save a few ounces. That said, for September and October backpacks, I find I sometimes need to put on many layers even in the 15 degree bag. I also go through warm and cool spells when I sleep -- sometimes wake up and I'm too cold, put on something and later wake up and I'm too warm. And then the whole cycle repeats...
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Re: Temperatures at higher elevations

Postby Hobbes » Sat Aug 13, 2011 9:17 am

quentinc wrote:I have a 15 degree bag -- it's a Marmot Helium

Getting a bag, down or otherwise, from a reputable mfg like Marmot (they use EN) solves a lot of problems. The only issues I have relate to the classic down v syn trade-offs.

I fall in the paranoid category, so like Jardine, my brother, and others, we all swear off down in the Sierra. I've had experience with hypothermia from surfing, and one semi-close call @ 11k, my brother had a very close call once in the winter (coincidentally, along Donner - imagine that :eek: ), and of course Jardine has his own two famous episodes which he relates in his book.

I mean, just for example, the stream crossings this year have been treacherous. One slip, and I don't care how carefully you've sealed your bag, and you might be SOL. As some here might have noticed, I almost always go solo, I tend to avoid popular trails, and I fish - all these add up to perhaps a higher risk.

The other issue, of course, is dew/condensation/rain, which practically dictates that you need to carry a 2-ply tent if going in with a down bag, rather than something UL like a silnylon tarp. So, at the end of the day, a 1lb down bag needs a 2lb tent, whereas a 2lb syn bag can get away with a 1lb tarp. Same difference.

Now, if you decide to go with syn, there's a whole world of trade-offs, because the stuff tends to degrade (ie lose its thermal efficiency) much quicker than down. And, of course, it's bulkier and doesn't possess the same thermal qualities (even the newest APEX is a poor comparison to 850 FP), so you're dealing with a heavier, bulkier bag than necessary if it isn't appropriate for the particular conditions.

Since I'm a bean-counter by trade, it was easy for me to pull together the basic research in order to design equip for my own needs, rather than rely on a commercial provider. I know where I go, how I go, and what I do when I get there - I want to minimize risk, but also minimize weight. Ergo, the detailed analysis.
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