Good morning, this is Sue Burak with the Inyo National Forest with an
   avalanche advisory posted for Friday, Dec. 19, 2008.

   MOUNTAIN WEATHER

   The National Weather Service issued a High Wind Warning last night for
   Mono County. Southwest wind gusts of 60-65 mph are forecast along 395
   through Friday afternoon. Average hourly wind speeds of 90 mph have
   been recorded on Mammoth and Mt. Warren with tidgetop gusts will
   exceeding 100 mph. There goes the powder skiing.

   Winds picked up yesterday morning and while the wind provided welcome
   mixing and adiabatic warming, it ruined a lot of fine powder skiing.
   Strong winds will continue through today and diminish by the late
   afternoon. Temperatures today at the 8,000 ft elevation will be a few
   degrees cooler than Thursdays balmy 32F, though still not as cold as
   earlier in the week. Expect only a few inches of new snow above 8,000
   ft while the higher elevations and Mammoth Mountain could see up to 8
   of new snow if the wind doesnt blow it away.

   The advertised dramatic drop in temperatures for the weekend has been
   revised upwards a few degrees to reflect the warmer air mass moving
   into the Sierra in front of the approaching Sunday into Monday storm.
   Lows will be in the single digits. The Sunday/Monday storm is a Tahoe
   event with the best of precipitation occurring Monday night for Mono
   County. By mid week, a subtropical moisture plume will bring a warmer
   Sierra storm to the area with possibility of several feet of new snow
   over Christmas.

   SNOWPACK AND AVALANCHE DISCUSSION

   There are a couple of avalanche concerns for the next few days. The
   most immediate concern is wind slabs. With plenty of new snow to move
   around, the wind upped the avalanche danger in a couple of hours in the
   areas we were skiing yesterday. Slab were forming in the trees on edges
   of broad open gullies.These newly formed wind slabs are sitting on the
   fresh snow from the weekend or on old snow surfaces.

   The other concern is the thick layer of fully developed depth hoar- the
   real Rocky Mountain variety especially where the snowpack is shallow.
   We found a rain layer from the November 1 storm sandwiched within the
   depth hoar layer in the Virginia Lakes area at an elevation of 10,000
   ft. The snowpack was shallow compared to Mammoth and was 18-20 deep.
   Two extended column tests showed no results while two of three
   compression tests failed easily with the third test failing in the
   moderate range. The ECT tests fracture propagation over a 90 cm column
   (35 inches) and is effective is differentiating between stable and
   unstable slopes. Check the website later today for the latest research
   on this valuable tool for assessing snow stability. Depth hoar is
   common in the Sierra snowpack and does not create the same degree of
   instability that depth hoar causes in other snow climates. However, the
   depth hoar in our shallow early season snowpack is concerning,
   especially since large faceted snow was the bed surface for the
   avalanche that caught a patroller off the Dragons Back on Tuesday.

   For the next two days, the main avalanche concern is wind slabs in the
   higher terrain. If you want to ski a steep slope, give yourself a good
   factual reason why you should ski that slope. We are tend to make up
   our minds that we will ski or ride a slope and ignore the facts that
   tell us the slope may not be the one to ski. One reason the Rutschblock
   is an effective test is that it is hard to ignore the results of a
   block sliding into the pit with one jump.

   BOTTOM LINE

   The avalanche danger today is rated MODERATE in mid elevation terrain
   in the trees. The avalanche danger rating for exposed, wind loaded
   terrain above treeline is CONSIDERABLE. The strong winds yesterday and
   last night loaded north to east facing terrain above treeline and steep
   slopes above 35 degrees are especially dangerous. Windslabs are
   widespread at the top of gullies and in broad exposed gullies. With
   plenty of powder to blow around, yesterdays snow banners were a red
   flag warning that unstable wind slabs have formed at the top of ridges,
   in open bowls and open slopes in the trees. Avoid hard, drum like wind
   slabs that may sound hollow especially in alpine terrain or beneath
   scoured ridgetops.

   Please note that the avalanche danger rating in this advisory expires
   in 24 hours. This advisory is our best interpretation of snow pack
   conditions and NWS forecasts issued today. Backcountry travelers should
   be aware that elevation and geographic distinctions are approximate and
   that a transition zone exists between upper and lower elevations.

   Avalanches do not happen by accident and most human involvement is a
   matter of choice not chance. Most avalanche accidents are caused by
   slab avalanches that are triggered by the victim of member of the
   victim's party. Even small slides can be dangerous. Always practice
   route finding skills and carry avalanche rescue gear. Remember that
   avalanche danger ratings are only general guidelines. Distinctions
   between geographic areas, elevations, slope aspects and slope angles
   should be made.