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Snow and Water levels 2011

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Re: Snow and Water levels 2011

Postby texan » Thu Apr 14, 2011 8:03 am

oldranger wrote:kpeter,

Key is water content which at this time of the year refers to ice. The more ice the longer it takes to melt. Some of the relatively lower elevation sites (+9,000 have over 50 inches of water. And you are absolutely correct. The temp and weather this spring will be critical factor. Last year my typical extrapolations didn't work quite right due to the cold and snowy spring. Right now I'm thinking that last weekend of june will be about the start of some fairly conservative backpacking opportunities and I'm scheduling my midsierra hiking beginning mid July and a high Sierra trip (up to 11,000) a couple of days later and about 10 days earlier than I would like but family obligations trump my backpacking schedule. I'm really looking forward to my September trip.

Mike


Hello you are absolutely correct about water content. At the Leavitt Lake site right now the water content is over 80 inches and the April average is just over 50 inches. That means the site is 160 PERCENT aboove normal. If we have a cold spring who knows when you will be able to get up in the high country. This year water content is similar to 82-83, 94-95, and 05-06. In all of those years I wasn't able to go to some of my favorite locations in the Sierra until mid- August. I think 94-95 was the worst thats when Mammoth Mountain had its longest season. It closed on August 13th 1995.

Texan



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Re: Snow and Water levels 2011

Postby kpeter » Thu Apr 14, 2011 10:31 pm

Thanks for the feedback, and good point on water content.

I've gone back and looked at the historical records based on water content and not on snow depth, and it does change things a bit. Unfortunately the Charlotte station does not have water content data that goes back to 1993, but my other four stations do. Here is how they stack up

Station; Elevation; Water Content on 4/14/2011; WC on 4/14/1993; Melt in 93; Melt in 2010

Kibbie Ridge; 6700; 34; 32; 29 June; 24 June
Ostrander Lake; 8200; 54; 63; 13 June; 15 June
Slide Canyon; 9200; 61; 57; 10 July; 27 June
Bishop Pass; 11200; 40; 40; 8 July; 30 June

Taking water content 1993 is the closest fit of any previous year. 1995 was considerably heavier than 1993 or 2011. These four stations are all very close fits to 1993, with only Ostrander Lake being more than 10% off and Bishop Pass being a perfect fit. I'll go with 1993.

As you can see, Bishop Pass and Slide Canyon melted out 8-13 days later in 1993 than they did last year in 2010. For Ostrander Lake and Kibbie Ridge the melt out in 1993 and 2010 was at about the same time.

Hypothesis: Lower elevations (Kibbie and Ostrander) seem to melt out at the same time each year regardless of the snow pack. Higher elevations may well melt out 10 days later than last year. It will be interesting to see if this turns out to be true.
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Re: Snow and Water levels 2011

Postby stevet » Fri Apr 15, 2011 7:25 am

kpeter wrote:1998 was extraordinary. It had quite a lot more snow (water content) than this year and its Spring must have been cool, with the melt-out not finishing at Bishop Pass until July 19. That is really late!



1998 was an extraordinary year. Several late springs storms. Snow was still accumulating into June. I scrubbed an early season sierra hike and walked the CDT through the Weminuche instead.
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Re: Snow and Water levels 2011

Postby tim » Tue Apr 26, 2011 12:30 pm

What about a comparison with 2006? That has the helpful advantage of being plotted on the CDEC average snowpack data each day: http://cdec.water.ca.gov/cgi-progs/prod ... OT_SWC.pdf
Obviously 2006 had an extraordinarily snowy April, but it looks like we are now tracking at or below 2006 as of the end of April. It also gives a hopeful benchmark for best case melt out after a very warm May (which was the case in 2006).
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Re: Snow and Water levels 2011

Postby kpeter » Sat Apr 30, 2011 6:44 am

tim wrote:What about a comparison with 2006?


That is a great point, since it illustrates something I have been discovering (a lot of you probably knew this, but spending a month digging through the data has convinced me): the snow depth or even the water content of a given year is not nearly as relevant as is the warmth of May and June. In otherwords, when I will get to backpack in the high country has much less to do with how much it snowed and a lot more to do with how fast it melts.

Charlotte Lake, for example, had 41" of water content on May 1, 2006 and was completely melted out by 13 June that year. But in 1998 Charlotte had an identical 41" of water on May 1 and wasn't melted out until 7 July. That is a 20 day difference in melt with identical snowpack.

In 1998, Charlotte had lost only about 10% of its water by June 1. In 2006 Charlotte had lost about 35% of its water by June 1. So May does make a difference.

The first two weeks of June is where most of the melt normally occurs, though. In 2006, the first 12 days of June melted the remaining 65% of the Charlotte snowpack. In 1998, however, these were cool weeks and Charlotte only lost 20%, and it was not until June 16-July 7 that it got warm enough to complete the melt.

I wish we could predict when the high country will open up on the basis of snowpack, but it's becoming clear to me that the depth of the snowpack is not the key variable, so much as the air temperature from May 1-June 15.
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Re: Snow and Water levels 2011

Postby tim » Sat Apr 30, 2011 8:24 am

Isn't the critical factor when the temperature stays above freezing overnight?
That is what I thought led to rapid melt out. At high elevations that doesn't happen often before June, whereas at lower elevations it happens in May. The CDEC data averages all the snow pack from low and high elevation sensors and shows rapid loss in May if it is warm - presumably this is coming mainly from lower elevations, and then the even warmer nighttime temps in June are needed to melt the snow higher up.

So what might be good to know is what (daily low?) temperature it needs to be in (say) Bishop or Mammoth or Yosemite Valley to be above freezing overnight at (say) 10000ft in that part of the Sierra. A 70 degree day might not melt as much snow as a 40 degree night. This coming week is expected to be warm, but I wonder how high the nighttime freezing level will be?
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Re: Snow and Water levels 2011

Postby Electra » Sat Apr 30, 2011 8:38 am

Yes on nighttime temps. Melt is slower the next day on the top level and an already compressed base layer can be further hardened overnight and his also prevents melt from percolating out the'bottom' and it adds/freezes in the middle layers, further adding to the base layer if that makes sense.
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Re: Snow and Water levels 2011

Postby Wandering Daisy » Sat Apr 30, 2011 1:46 pm

CDEC data is great, but do not forget its purpose- prediction of water storage and potential flooding. The emphasis is on "water equivelent", not snow depth. The sensors are located to give a statistical sampling of the upper watersheds of the major downstream rivers. It is critical to look up the location data on each sensor - is it in an open field? or in the trees? on the north slope? or the south slope? A sensor may show 100 inches of snow, and there can be 50 inches of snow hundred of yards away on a different slope orientation.

Personally, I use the snow data to have a heads-up on the potential of snow travel and gear up appropriately. High snow years do not stop me, I just pack and plan differently. Mainly, I take more care in making sure there are bridges where I cross creeks. I spent many years backpacking in Wyoming, and if you were not willing to walk on snow, you lost half your backpack season. You have to have a different strategy - walk early in the day if you are sinking in, do passesw later in the day if it is icy and too hard. You can usually find dry spots to camp. My favorite campsite in early season is on top of a flat rock. I am actually excited about the high snow year!
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Re: Snow and Water levels 2011

Postby kpeter » Sat Apr 30, 2011 3:58 pm

The data is very inaccurate in a whole bunch of different ways. For example, the sensor data almost always shows less than the hand measured data, and I have noticed numerous blips where the sensor is obvious malfunctioning. I've been dropping certain locations and taking others just because some sensors were working better during our comparison years.

None of that inaccuracy really matters, though, if you are using the data strictly for comparisons across seasons. The gauges do reliably show you the day they run dry. And if they are on a sunny south slope in 1998 they will also be on a sunny south slope in 2006 (at least those alpine sensors!)

My goal is to figure out which other year this season best resembles, and then we will know that the conditions this year will most closely resemble the conditions from that known year. We could all chime in with our memories of the snow in year XXXX as a way of knowing what to expect in 2011. So far, the nominees include 1993, 1995, 1998, and 2006. Based on snowfall alone we are best matched by 1993. However, which year we ultimately end up resembling most closely will depend mostly upon the warmth of May and early June.

In a couple of days, when we have the May 1 data, I will let you know how we compare with the four candidate years as of May 1.

I agree, WD, that walking on snow is no barrier to some people and even enjoyable. I don't mind it, just so long as I do not have to cross dangerous fords or passes. There, I'm very conservative, and since I'm planning a long loop trip I don't want to start it and find my way is blocked. People, myself included, are prone to take undue risks when they are halfway through a trip and find a barrier. And so I am a little obsessive/compulsive when it comes to planning to avoid such things--it sounds like you are too--looking for trips with bridges, etc.
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Re: Snow and Water levels 2011

Postby Electra » Sat Apr 30, 2011 4:12 pm

I think this year will resemble 1995. That year, most everything above 10,500 was snow covered until mid to late august. Any pass above 11k on the muir trail had snow for miles, muir pass had snow down to just above sapphire until mid august. I recall guiding a cross country trip near black giant and langille peaks in northern kings in mid august and up on the flanks were 15 foot slabs and drifts in spots. Very impressive.
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Re: Snow and Water levels 2011

Postby kpeter » Sun May 01, 2011 7:09 am

The May 1 data is in and I am surprised. This is NOT shaping up to be a late snow year, so far.

Most of the stations have less water content than all four of the comparison years (2006, 1998, 1995, and 1993.) In the four comparison years very little if any melt happened in April--May 1 was pretty much the high point in all four years. In 2011, however, all the stations show some significant melting occuring in April.

So we are ahead of the usual melt so far, although this early in the season it would be easy for a cooling trend to reverse that.

I've been trying to monitor every working automatic station that is above 10,000 feet (there are not very many of them, actually), and none of them are showing any more water content than ANY of the four comparison years. The closest matches are 1993 and 2006. A few, like Bishop pass and Chagoopa Plateau are lower than last year.

Conclusion: the melt is ahead of 2006, 1998, 1995, and 1993 as of May 1.
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Re: Snow and Water levels 2011

Postby texan » Sun May 01, 2011 10:36 am

I think it depends where your at in the Sierras. The water content at Leavitt Lake on May 1st is around 86 inches. There are only two years that have a higher reading (82 and 95). Also Leavitt Lake usually has the most snow in the Sierras according to the snow sensor data. I know because I have been looking at it for years.
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