Avalanche Advisory: Sunday - Dec 30, 2018

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THIS AVALANCHE ADVISORY EXPIRED ON December 31, 2018 @ 6:50 am
Avalanche Advisory published on December 30, 2018 @ 6:50 am
Issued by Chris Engelhardt - Eastern Sierra Avalanche Center

Natural and human triggered avalanches will be unlikely today. Small avalanches in isolated or extreme terrain could be possible where Northerly winds have developed wind slabs. Terrain that will be loaded from the N-NE winds will be W-SW-S-SE aspects near and adjacent to ridgeline in the upper elevations.  Always maintain sound foundational protocols for backcountry travel, so you are practiced and prepared when avalanche conditions do increase.

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Below Treeline
Avalanche Problem 1: Wind Slab
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Northerly winds continued to rake the high country Saturday and visible plums of snow were streaming from the high peaks in the Mammoth Lakes area (see 12/29 San Joaquin Ridge Observation).  Seeing the snow aloft indicates that there is still enough snow available to be transported by the winds to the S-W aspects.  Recent low density snow (2-4”) combined with the Christmas Eve (5-8”) snowfall has provided the loose material for the winds to move.  Although there is likely not enough snow being deposited on the S-W aspects to develop avalanche activity, standard precaution should be taken in topography such as gullys adjacent to arêtes/ridges and other terrain features that are capturing suspended snow.

advisory discussion

Since our good start at the beginning of December and a few exciting days (12/8-12/10) with sensitive wind slabs being triggered in the alpine, conditions have become fairly monotonous and un-exciting in relation to avalanche activity the past 2 weeks. Most of the N-NE alpine terrain right now is scoured and stripped from our lengthy dose of northerly winds, and the sunnier aspects of W and S just have yet to build up much snowpack. In general, the snowpack is stable as observed in accessible terrain, and no natural avalanches or human triggered avalanches have occurred for some time. There has not been any glaring or surprising results with stability tests in the forecast area and overall snow depths are wavering on the thin side. There are wide spread residing conditions to keep track of with faceting snow layers, windboard deposits, and recent surface hoar development (see 12/28 mammoth bowl obs), but nothing of major concern at the present time.  Deepest snow total measurements have been taken on the east side of the Mammoth crest  at 120-160cm. Most other mid to upper non-wind loaded slopes average 60-90cm of snow and the lower elevations are struggling at 15-30cm. We should be thankful that we have had extended periods of fairly cold weather to preserve what snow we've got thus far this season. In the hope of future snow storms and better conditions, it’s a good time to hone the backcountry skills, get the gear spruced up and head out with friends for a little Avalanche Transceiver practice. 

Weather and CURRENT CONDITIONS
weather summary

A warmer day with above freezing temperatures is slated for middle and upper elevations today. Partly cloudy conditions leading to sunny skies with moderating wind speeds will make for a pleasent travels in the mountains. N winds continued through the night in the 30mph range and switched to the WSW early this morning. NW winds are still expected today although at much lighter (10-15mph) overall speeds with 50mph gusts at ridge tops. A decrease in the north wind will be a nice rest from the beating we've taken the past 3 days. We may get some snow flurries for New Years Eve, and speculation of a pattern change for snow hovers on the horizon over a week out. Some good New Year's resolutions may bring some snow to the forecast area.

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8,000 ft. to 10,000 ft.
Sunday Sunday Night Monday
Weather: Partly cloudy then becoming sunny Partly cloudy Partly cloudy. Slight chance of snow showers
Temperatures: 37 to 43. deg. F. 9 to 14. deg. F. 15 to 21. deg. F.
Mid Slope Winds: Northwest 10 to 15 mph with gusts to 40 mph. Northwest 10 to 15 mph with gusts to 40 mph. Northeast 10 to 15 mph with gusts to 50 mph.
Expected snowfall: 0 in. 0 in. 0 in.
Over 10,000 ft.
Sunday Sunday Night Monday
Weather: Partly cloudy then becoming sunny Partly cloudy Partly cloudy. Slight chance of snow showers in the afternoon
Temperatures: 30 to 35. deg. F. 6 to 11. deg. F. 10 to 15. deg. F.
Ridge Top Winds: Northwest 25 to 35 mph with gusts to 55 mph decreasing to 15 to 30 mph with gusts to 45 mph in the afternoon. Northwest 20 to 35 mph. Gusts up to 55 mph decreasing to 45 mph after midnight. Northeast 25 to 40 mph with gusts to 60 mph.
Expected snowfall: 0 in. 0 in. 0 in.
Disclaimer
This Avalanche Advisory is designed to generally describe avalanche conditions where local variations always occur. This product only applies to backcountry areas located outside established ski area boundaries. The information in this Snowpack Summary is provided by the Eastern Sierra Avalanche Center, who is solely responsible for its content.

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