Good afternoon. This is Sue Burak with the Eastern Sierra Avalanche
   Center with a backcountry avalanche warning posted on Saturday February
   23, 2008.

   A SPECIAL AVALANCHE ADVISORY IS IN EFFECT FOR THE EASTERN SIERRA FROM
   SONORA PASS SOUTH TO MT WHITNEY. STRONG WINDS AND HEAVY SNOWFALL WILL
   CREATE DANGEROUS AVALANCHES IN THE HIGHER ELEVATIONS AND THE DANGER IS
   EXPECTED TO REACH HIGH BY EARLY SUNDAY MORNING. AS SNOWFALL AND STRONG
   WINDS CONTINUE ON SUNDAY, THE AVALANCHE DANGER MAY RISE TO EXTREME.

   MOUNTAIN WEATHER

   After phone discussion with NWS in Reno, there is a very good
   probability that over 4 feet of snow will fall above the 9,000 ft
   elevation in Mono County. Models indicate 3 feet of snow could fall at
   the 7,000 ft elevation. This is one of the most impressive storms I
   have seen in a while: check out
   http://squall.sfsu.edu/gif/sathts_pac_500_00.gif

   The low is still off the West Coast and rain is falling in the San
   Francisco area. Light snow is falling from the Sherwin Summit to north
   of June Mountain. Snow levels may rise to 7,000 ft this evening but
   then drop to the 6,500 ft elevation. The Owens Valley will see rain at
   the valley floor.

   There is a winter storm warning for Inyo and Mono counties for this
   afternoon through Sunday night. For the southern Sierra, 20-30 inches
   of new snow is expected above 8,000 ft by Sunday evening. Strong and
   gusty winds over 70 mph are likely in the southern Sierra with whiteout
   conditions. For Mono County, 2 to 3 feet of new snow is expected above
   7,000 ft by Sunday morning. Terrain above 9,000 ft could see 4 ft of
   new snow by Sunday night.

   As the jet stream passes over the Tahoe area, winds in Mono County will
   reach 50 mph along 395 and over 130 mph on exposed ridgetops. Storm
   wind directions will begin from the south and southeast and shift to
   the southwest by Sunday. Temperatures for Saturday and Sunday will
   range from the teens to low 20s.

   SNOWPACK AND AVALANCHE DISCUSSION

   The only thing that could make conditions worse would be a buried
   surface layer deep in the pack. Things are bad enough with up to 4 feet
   of higher density snow falling on top of 1.5 to 2 feet of 6% snow from
   the Thursday night and Friday storm, though Mammoth Mountain reported
   11%.

   Snow stability yesterday was good in non wind loaded areas- this was
   helpful as we needed steep terrain to keep skis turning through two
   feet of new. Stuffblock tests and extended column tests had hard
   results. The old snow/new snow layer seemed well bonded at the 10,000
   ft elevation in Rock Creek. Control results from Mammoth Mountain
   showed steep slopes went on hand charges on either density changes in
   the storm snow down to the old sun crust.

   With forecasted snowfall rates of 2-3 inches an hour for tonight and
   tomorrow, it is easy to visualize the load being applied to yesterdays
   snow. Add the additional loading brought on by strong winds and the
   probability of large,deep avalanches running to the old snow surfaces
   of the last two weeks increases. A widespread avalanche cycle is
   expected to occur during this storm.

   BOTTOM LINE

   The avalanche danger rating increases to HIGH this evening. Natural and
   human triggered avalanches are likely. Likely means it is almost
   certain a light load will trigger an avalanche. Unstable slabs will be
   found on a variety of aspects and slope angles. Travel in avalanche
   terrain is not recommended.

   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.