Snow and Water levels 2011

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kpeter
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Re: Snow and Water levels 2011

Post by kpeter »

Here are the latest snow depths as of April 13

Format = Station; elevation; depth two weeks ago; depth on the 13th

Kibbie Ridge; 6700; 95.8; 61
Ostrander Lake; 8200; 156.1; 124
Slide Canyon; 9200; 147.6; 119
Charlotte Lake; 10400; 143; 112
Bishop Pass; 11200; 118.5; 96

As you can see, we had a warm first half of April and depths are already coming down. However, when I checked the water content the levels had not come down nearly as much as snow depth. It is getting warm enough to melt the top layers which drain into lower levels and refreeze, making our famous Sierra concrete. Still, this is the normal progression.

Looking at the progression at Bishop Pass I note that there are 40 inches of water content there as of April 13. On April 13, 1993, there were 40 inches of water content there. We seem to be exactly on the 1993 progression. In 1993 passes melted out before they did last year, even though 1993 (and 2011) had more snow than last year.

Conclusion so far: If April, May, and June all stay as warm as the first two weeks of April have been then this will not be a particularly late snow year for backpacking, despite the heavy snowpack. It all hinges on the next 8 weeks of air temperature.
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oldranger
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Re: Snow and Water levels 2011

Post by oldranger »

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
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texan
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Re: Snow and Water levels 2011

Post by texan »

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.

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kpeter
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Re: Snow and Water levels 2011

Post by kpeter »

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

Post by stevet »

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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tim
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Re: Snow and Water levels 2011

Post by tim »

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" onclick="window.open(this.href);return false;
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

Post by kpeter »

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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tim
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Re: Snow and Water levels 2011

Post by tim »

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

Post by Electra »

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

Post by Wandering Daisy »

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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