Eastern Sierra Avalanche Forecast - 3/23/14

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THIS AVALANCHE ADVISORY EXPIRED ON March 24, 2014 @ 6:38 am
Avalanche Advisory published on March 23, 2014 @ 6:38 am
Issued by Sue Burak - Inyo National Forest
bottom line

The avalanche danger is generally LOW for the Mammoth Basin and June Mountain areas. The avalanche danger rating for the Rock Creek area is Low, though caution is advised in steep terrain where a thick layer of depth hoar continues to show the snowpack is weak. Low danger never means no danger. Today you could find shallow wet sluffs in steep terrain with daytime heating. 

 

The avalanche rose is filled out for alpine and mid elevation terrain in the trees. Areas with grey shading either have no snow or there is no snowpack information available from these aspects and elevations. 

How to read the advisory


  • Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

Bottom Line

The avalanche danger is generally LOW for the Mammoth Basin and June Mountain areas. The avalanche danger rating for the Rock Creek area is Low, though caution is advised in steep terrain where a thick layer of depth hoar continues to show the snowpack is weak. Low danger never means no danger. Today you could find shallow wet sluffs in steep terrain with daytime heating. 

 

The avalanche rose is filled out for alpine and mid elevation terrain in the trees. Areas with grey shading either have no snow or there is no snowpack information available from these aspects and elevations. 

  • Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
Avalanche Problem 1: Loose Wet
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The pattern of cold nights and mild daytime temperatures and cloud cover reduced the possibility of wet snow sluffs. Today will be sunny and warmer - with daytime heating, watch out for sluffs in steep east and southeast facing terrain around rocks that absorb more heat. We still have cool weather and the warming trend advertised by the NWS is mild compared to warm spells in January and February. . 

Avalanche Problem 2: Persistent Slab
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Persistent slabs are a tricky problem, especially above 10,000 ft in Rock Creek. Spring snow is found at mid elevations but high north through east facing terrain is still winter snow and weak facets or depth hoar are found at the bottom of the snowpack. Recent fracture propagation with sudden collapse failures on the basal depth hoar at high elevations in Rock Creek are a reminder that this layer is still capable of producing an avalanche in very steep terrain- the odds of triggering an avalanche on depth hoar on the ground is low but normal caution and common sense is always appropriate. Avoid slopes steeper than 35 degrees in areas with a relatively thin snowpack. 

advisory discussion

Persistent slabs are a tricky problem now as spring snow is found at mid elevations but high north through east facing terrain is still winter snow and weak facets or depth hoar on the bottom of the snow pack. Recent fracture propagation with sudden collapse failures on the basal depth hoar at high elevations in Rock Creek are a reminder that this layer is still capable of producing an avalanche in very steep terrain- the odds of triggering an avalanche on depth hoar on the ground is low. Avoid slopes steeper than 35 degrees in areas with a relatively thin snow pack. 

recent observations

Observations in an east facing bowl above 10,000 ft in the June Mountain area revealed the first snowpit in weeks that did not have depth hoar at the bottom. Instead, there was 10 cm (4 inches) of solid faceted particles. Two prominent melt freeze crusts with small facets below each crust bounded the February and early March storm slabs. Compression and extended column tests had no results, ECTX. Snow depths were around 3 feet. 

Exposed slopes had varying sizes of sastrugi alternating with wind drifted firm snow. North slopes were firm with areas of breakable wind board. East slopes were icy sastrugi.  Below 10,000 ft, areas of spring-like snow were found. No loose wet snow releases were observed. Numerous old crowns from the natural avalanche cycle in early March were seen on NE aspects under ridge lines. 

CURRENT CONDITIONS Weather Observations Between June (10,000 ft.) and Mammoth (11,000 ft.)
0600 temperature: 24 deg. F.
Max. temperature in the last 24 hours: 44 deg. F.
Average wind direction during the last 24 hours: NE, SW
Average wind speed during the last 24 hours: 10 mph
Maximum wind gust in the last 24 hours: 26 mph
New snowfall in the last 24 hours: 0 inches
Total snow depth: 38 inches
weather

After a couple of cool, breezy days, a ridge of high pressure builds today bringing above average temperatures today and tomorrow. On Tuesday, a low presure system drops into northeast California bringing snow to the higher elevations on Tuesday and Wednesday. 

High elevations will be sunny with light east winds. Expect highs in the mid 40's above 10,000 ft. Mid-elevations will warm up to the upper 40's and low 50's today. 

Snow is expected on Tuesday and Wednesday. There is alot of moisture associated with this storm but forecast models are uncertain regarding snowfall amounts. 

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: sun clear sun
Temperatures: 47 deg. F. 22 deg. F. 49 deg. F.
Wind direction: East NE south
Wind speed: 5 5 5
Expected snowfall: 0 in. 0 in. 0 in.
Over 10,000 ft.
  Sunday Sunday Night Monday
Weather: sun clear sun
Temperatures: 45 deg. F. 25 deg. F. 46 deg. F.
Wind direction: East NE south
Wind speed: 5-10 5 5-10
Expected snowfall: 0 in. 0 in. 0 in.
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