Good morning, this is Sue Burak with the Inyo National Forest with your
   avalanche advisory for Wednesday, Dec. 24, 2008. 
   MOUNTAIN WEATHER
   The next storm should be a Big Christmas present for all backcountry
   skiers and riders- after the avalanche danger has subsided. The storm
   for Christmas Day will come down harder and be more significant in
   terms of water content and snowfall than previous storms this winter.
   This means higher density snows than the fluff that fell last weekend.
   Add a good period of strong winds along with the higher density snow
   and we have the ingredients for high avalanche danger from wind slab
   avalanches.

   By the time the storm moves east Thursday night, there could be several
   feet of new snow above 9,000 ft in Mono County and up to two feet of
   new for the high elevations of Bishop Creek south to Whitney.

   A winter storm warning has been posted from 4 PM Wednesday through 4 PM
   Thursday for the Sierra in Inyo County. Snow is expected to begin over
   the southern Sierra Wednesday afternoon and continue through most of
   Christmas Day. Snow will be heavy at times and expect over 1 foot of
   snow above 8,000 ft. In addition...strong winds will develop over the
   Sierra Crest early Christmas Day which will cause blowing and drifting
   snow. Expect significantly colder temperatures Thursday night.

   For the mountains of Mono County: WINTER STORM WARNING REMAINS IN
   EFFECT FROM 4 AM WEDNESDAY TO 12 PM PST THURSDAY...SNOW WILL MOVE INTO
   THE SIERRA WEDNESDAY MORNING WITH PERIODS OF HEAVY SNOW WEDNESDAY
   AFTERNOON THROUGH THURSDAY MORNING.TOTAL SNOW ACCUMULATIONS: 5 TO 10
   INCHES BELOW 7000 FEET AND EAST OF HIGHWAY 395 IN MONO COUNTY. 18 TO 36
   INCHES OF SNOW IS EXPECTED IN THE HIGH SIERRA. SOUTHWEST WINDS OF 15 TO
   30 MPH WITH GUSTS UP TO 50 MPH WEDNESDAY NIGHT AND THURSDAY WILL CREATE
   AREAS OF BLOWING AND DRIFTING SNOW. LOCAL GUSTS TO 60 MPH ARE POSSIBLE
   IN WIND PRONE AREAS. RIDGE GUSTS OF UP TO 130 MPH ARE POSSIBLE.

   The first low impacts southern California today with the bigger low and
   the big snowproducer for the Sierra coming in Wednesday evening and
   Christmas Day. Locations east of the Sierra Crest will be shadowed out
   of the bulk of the precipitation but expect snow in Bishop, Tom's
   Place, Aspendell and Lee Vining by sunrise on Christmas Day.

   Temperatures will warm to the mid and upper 20's for the next two days
   but drop Thursday night. Ridging will occur Friday. The long term
   pattern could be unsettled as a moist jet flows over the PNW for 7
   days. if the jet sags south, the Sierra will receive snow.

   SNOWPACK AND AVALANCHE DISCUSSION

   Conditions are sketchy out there! There are numerous reports of skiers
   experiencing tree shaking slope settlement along with shooting cracks.
   Thanks to the Southern California nordic ski patrol for their thorough
   observations. Also thanks to the phoned in reports from local skiers.
   All report seeing the fist hardness layer of depth hoar previously seen
   in Virginia Lakes, with stability tests failing in the easy range.
   Skiers reportedly left an area off the Mammoth Crest because of
   shooting fractures in the surface wind affected snow.

   There are two primary concerns today and tomorrow. With high density
   snow forming wind slabs in exposed terrain, watch out for freshly
   formed wind pillows today on the lee side of ridges and gullies. Any
   wind loaded slope will be especially dangerous and should be avoided.

   The second, less obvious concern, is the weak snow at the bottom of the
   snowpack. Conditions have allowed the weak depth hoar layer to persist
   and the weak faceted snow has not gained strength. The upcoming storm
   will add significant weight to the prexisting snow. With the snow
   already in a weakened state, expect rather unstable conditions on all
   mid to upper elevation slopes. Additional loading will increase the
   avalanche danger from Moderate to the Considerable and High ratings.

   BOTTOM LINE
   The avalanche danger rating today is MODERATE. Dangerous avalanche
   conditions exist on steep exposed slopes and convex terrain features.
   Pay attention to newly formed wind pillows and avoid rock outcrops
   where large areas of weak depth hoar can be found. Evaluate the snow
   and terrain carefully and use good travel habits.

   The avalanche danger rating will increase towards the end of the day as
   the storm moves in and accumulations exceed 6-10 inches. This advisory
   will be updated on Christmas Day.

   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.