[pct-l] Sierra Snow

[goslowgofar at yahoo.com (goslowgofar)]

Here's an excerpt from the Tuolumne Meadows winter rangers' report:

Park News

TUOLUMNE MEADOWS - WINTER CONDITIONS UPDATE - March 23, 2005

WEATHER: (from March 17 to March 23)

High temp: 41° (March 21)

Low temp:  5° (March 21)

New snow: 59?(March 18-23)

Total settled snow depth: 97? (March 23) Deepest depth so far this winter and spring.

 

SKIING CONDITIONS: Back to trail breaking conditions. With five feet of new snow it will be awhile before we see the return of last week?s spring conditions. The new snow can settle fast this time of year although new snow depth may vary widely with altitude and aspect (see avalanche discussion).  

 

AVALANCHE/SNOW CONDITIONS: (above 8000?) Avalanche danger is CONSIDERABLE and avalanche consequences are also very considerable with five feet of new snow on a firm base in the last few days. Be extremely cautious of wind loaded slopes formed during strong SW winds. If you only consider the steeper wind loaded slopes the avalanche danger would be HIGH.

 

DISCUSSION: Two storms over the last weekend and early part of this week left us with five feet of new (not so light) snow. Strong SW winds also accompanied these storms leaving some wickedly deep wind loads on lee slopes. On Monday the 21st (the only break in this storm series) we found some 5-6 foot wind loads at tree line on Unicorn Peak. Some of the steeper roll over areas (change in slope) had so much blown in snow they appeared much smoother than before. We also saw evidence of several sizable slab avalanches off the lee side of the Cathedral Range with crown fractures of 5 feet or more. At about 10,000? on a N aspect and 37º slope we tried isolating shovel size columns of snow which either collapsed in the digging or failed after one finger tap on a shovel. The failure took place 2 ½? deep at the interface between the old snow surface and the newly fallen snow. Now add another 3-4 feet of heavy new snow on top and you have present conditions, yikes.

Altitude and aspect can create quite a difference in snow conditions. On the same Monday that I described above we found the old snow/new snow interface quite different on the south facing side of Lembert Dome at 8,600?. The snow pack down lower, and on many south aspects, had turned isothermal (32º F throughout) last week and assimilated or melted the new snow much more quickly. At Lembert we found 8?of new snow sticking to the wet corn snow surface underneath forming a reasonably good bond. Of course another 3 feet of snow has also fallen since then, enough to stress any bond.

 

WILDLIFE: Just before this storm cycle we spotted our first Violet-green Swallows winging their way westward. They were low to the ground as they zipped past us on top of Pothole Dome. Another pre-storm report from Bill who was staying at the ski hut: he saw several Gray-crowned Rosy Finches bathing in the snow surface melt water near the summit of Mammoth Peak. I guess they knew about the coming storm and that it would be awhile before their next bath.  

 



Hiker97@aol.com wrote:
I went to the Bear Valley website and this is what it said:

"The latest storm has delivered 54 inches of fresh snow as of Wednesday at 
8:00am, with 20 inches falling in the past 24 hours! Check the hourly log for 
more details." 

Go to www.bearvalley.com.

Later, Switchback



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