Eastern Sierra Avalanche Forecast - 12/28/14

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THIS AVALANCHE ADVISORY EXPIRED ON December 29, 2014 @ 7:00 am
Avalanche Advisory published on December 28, 2014 @ 7:00 am
Issued by Sue Burak - Inyo National Forest
advisory discussion

Most of the snowpack structure consist of new dry powder snow sitting on top of the widespread thick crust that formed following the Dec 20-21-22-23 warming event, but there are areas on slopes without the crust.  In either case, the snowpack is not reacting in extended column tests. Small facets are found in a 6 inch thick layer above the ground and above the crust that separates the end of November snow to the early December snow. Total snowpack depths ranged from 20 to 30 inches- it appears there is more snow on the ground than there really is- hitting rocks is to be expected as part of the day’s skiing adventure.

recent observations

Isolated pockets of small, shallow, unstable wind slabs were observed along east and northeast slopes at the top of bowls along the San Joaquin Ridge. Blowing snow during the storm and northeast winds created small shallow wind slabs- surprising to find wind slabs on northeast aspects when the winds at the top of Mammoth have been from the northeast but it is a good reminder that winds at the top of Mammoth can be isolated to the mountain while winds on the Sherwins will be from a different direction. Experienced backcountry users know the wind speed and direction recorded at the top of Mammoth may not reflect local conditions.

The snowpit is 38 cm in depth. The crust that formed during last week's warm weather can be seen with about 8 cm of new snow ( 3 inches). 

An observer reported wind stripped conditions at the top of Red Cone with numerous ski tracks in the middle sections of the bowl. Snow depths ranged from 4" near the top of the bowl to about 2 ft at the bottom of the bowl. 

CURRENT CONDITIONS Weather Observations Between June (10,000 ft.) and Mammoth (11,000 ft.)
0600 temperature: 14 deg. F.
Max. temperature in the last 24 hours: 28 deg. F.
Average wind direction during the last 24 hours: WSW
Average wind speed during the last 24 hours: 20 mph
Maximum wind gust in the last 24 hours: 45 mph
New snowfall in the last 24 hours: 0 inches
Total snow depth: 21 inches
weather

Expect below normal, but not record breaking, cold temperatures Tuesday-Thursday this coming week. Light snow showers are expected Monday night and Tuesday. 

A strong cold front is projected to barrel through Monday night into Tuesday. There may be a few snow showers in the mountains but nothing more than an inch or two is expected.  Forecasters are confident a period of strong east to northeast winds could impact our area. As a massive high pressure ridge builds off the coast of Canada into the Gulf of Alaska, a deep trough digs down the east side of the ridge, a favorable setup for “inside sliders” to produce a few inches of snowfall. The only positive benefit of a building ridge is that the farther north the ridge shifts, storms may be able to move onto the West Coast.

For the next two days, daytime highs gradually warm a few degrees to seasonal temperatures in the upper 30's. Nights will remain in the teens. North winds will be light to moderate along the high elevation ridgetops, shifting to the west and southwest later today.

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: sunny sunny sunny
Temperatures: 35 deg. F. 13 deg. F. 32 deg. F.
Wind direction: W SW SW
Wind speed: 10-15 10-15 15-25
Expected snowfall: 0 in. 0 in. 0 in.
Over 10,000 ft.
  Sunday Sunday Night Monday
Weather: sunny clear sunny
Temperatures: 32 deg. F. 12 deg. F. 27 deg. F.
Wind direction: NW W W
Wind speed: 20-30 30-35 30-40
Expected snowfall: 0 in. 0 in. 0 in.
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