Good morning, this is Sue Burak with the Eastern Sierra Avalanche
   Center with an avalanche advisory posted on Saturday, February 16,
   2008. 

   Tonight, Ned Bair from the UCSB Bren School and I will be hosting a
   Nerd Night at 6 PM at the Mammoth Community Water District. I will
   talk about teleconnections; how the weather and climate around the
   world is strongly linked to weather and climate in other places
   through atmospheric connections. The Madden Julian Oscillation, El
   Nino and La Nina will also be discussed. Ned will present his findings
   on Patterns of slab avalanche release on Mammoth Mountain, a
   presentation that is sure to challenge the nerdiest of snow nerds.

   MOUNTAIN WEATHER
   
   The wind storm of Wednesday moved south and east and created
   significant snow for the mountains east of Los Angeles as well as
   Flagstaff and central New Mexico.

   Friday's temperatures were 20-25 degrees F warmer than Thursday's with
   Bishop warming from 42 F on Thursday to 59 F on Friday afternoon.
   Todays mountain temperatures will climb a few more degrees and remain
   in the mid to the upper 40s. Night time temperatures have also warmed
   15 to 20 F into the mid 20s in mountain locations above the inversion
   that keeps lows in Lee Vining, Crowley Lake and Toms Place in the low
   teens.

   North winds will calm down today with ridgetop gusts in the 30-40 mph
   range.

   A pattern change from dry to wet weather is expected mid week. After a
   couple of weak shortwaves break down the ridge, a strong mid latitude
   jet will bring a succession of wet storms into central California for
   Wednesday night through Friday

   SNOWPACK AND AVALANCHE DISCUSSION

   After two cold and windy days, snowpack temperatures in the upper 6
   inches of the pack have cooled off to -6 to -14 C on north and east
   aspects above 9,000 ft. Mid pack temperatures are warmer- temperature
   gradients and the resulting vapor pressure gradients are conducive for
   faceting to occur in the upper 4- 6 inches of the pack and water vapor
   moves from areas of high concentration to areas of low concentration.
   Strong gradients are turning rounds to facets. This process will
   continue on high north and east aspects for the next day or so and do
   not pose a stability problem right now. This layer will have to be
   monitored to see if gradients lessen before the weather changes next
   week.

   In the meantime, clear night time skies and light winds are the
   perfect conditions for surface hoar formation. Look for the sparkly,
   feather like crystals on open slopes the next few mornings.

   With little, if any new snow falling Thursday, I found only a few
   isolated pockets of wind drifted snow below the ridge tops today. I
   did not see any point releases today on southern aspects but this will
   change as snow temperatures increase in the upper 4-6 inches of the
   snowpack. However, I do not anticipate widespread wet snow instability
   because light north winds are forecasted to continue and temperatures
   are not expected to reach the mid to upper 50s as they did during the
   first few days of the week.

   BOTTOM LINE
   The avalanche danger rating remains LOW. This is a good time to ski
   big lines if you are not picky about skiing good quality snow from top
   to bottom. Many ridge top approaches have been stripped bare by
   southwest and north winds and exposed slopes can be very firm.

   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.