Eastern Sierra Avalanche Forecast - 1/9/14

Avalanche Advisory published on January 9, 2014 @ 7:57 am
Issued by Sue Burak - Inyo National Forest

We are waiting for snow. There is not enough snow to warrant regional danger ratings. For an update on snowpack conditions, see the text discussion.

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advisory discussion

With sparse snow cover, there is a high level of variability in snow depths but not in the snow structure. Snowpack depths range from bare to 4” to 32” depending on aspect, elevation, slope configuration and whether slopes are shaded or non-shaded.  

The “snowpack” in the Rock Creek area is shown below.  The snow structure is similar in shallow north aspects. The sun crusts at the snow surface and within the “snowpack” assist the faceting process.

The depth hoar of today is the same depth hoar of a month ago because depth hoar has been shown to recycle over and over. Depth hoar and facets are increasing in size and the texture is becoming coarser due to the water vapor moving through the snow and encountering barriers to vapor transport in the form of multiple sun crusts.  Ned Bair recently reported 2 meter ECT’s propagating on steep shaded north aspects in the Red Lake area.

The snowpack contains a several persistent weak layers: depth hoar from October and November snow, a thick layer of large facets resulting from the biggest snowfall of this miserable year, December 3-6, and a couple of thin layers of facets formed from mid and later December snow.  

As the dry, clear weather continues, so does the faceting process. Possible weather scenarios include small cold “inside slider” storms that bring only a few inches of new snow, adding to the smorgasbord of weak layers. This happened last winter after the December storms. The scenario we all hope for is a multiday, multi footage event that will open up the backcountry and add water to offset the current drought. The downside is that big snows will bury these persistent weak layers, create storm and wind slabs and create unpredictable avalanche conditions.  Given a choice, I’ll take big storms and avalanche conditions over shallow snow anytime.

weather summary

The National Weather Service forecast calls for mostly sunny skies today- however, skies are cloudy and southwest winds are blowing 30-40 mph, gusting to 50 mph. Expect mostly cloudy skies, colder temperatures and gusty southwest winds today as a weak system rides over the entrenched high pressure ridge. Highs will reach the mid 30’s today, falling 10 to 15 degrees from yesterday. Higher elevations will be about 10 degrees colder with highs in the upper 20’s.  

As a side note, winter weather advisories are posted for north east Nevada- SNO-TEL sites at 8,000 ft. show snow depths of 22-23” compared to 14” at the Sesame Street study plot and 19-20 inches on the Mammoth Pass snow pillow. A similar situation existed last winter with storms riding over the ridge and snowing in central Nevada.

The main weather story is the wind- west and southwest winds 25 to 35 mph with wind gusts over 55 mph have been recorded at … There is slight chance of an inch or two of snow today.

Friday will warm up back to the mid to upper 40’s under sunny skies.

This morning’s NWS discussion mentions a chance for a pattern change after January 17.

Weather Observations Between June (10,000 ft.) and Mammoth (11,000 ft.)
0600 temperature: 18 deg. F.
Max. temperature in the last 24 hours: 45 deg. F.
Average wind direction during the last 24 hours: sw
Average wind speed during the last 24 hours: 25 mph
Maximum wind gust in the last 24 hours: 55 mph
New snowfall in the last 24 hours: 0 inches
Total snow depth: 14 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8,000 ft. to 10,000 ft.
Thursday Thursday Night Friday
Weather: mostly cloudy partly cloudy partly cloudy
Temperatures: 33-39 deg. F. 16-23 deg. F. 46.52 deg. F.
Mid Slope Winds: SW and W NW 6NW
Expected snowfall: 0 in. 0 in. 0 in.
Over 10,000 ft.
Thursday Thursday Night Friday
Weather: mostly cloudy partly cloudy partly cloudy
Temperatures: 27-33 deg. F. 16-22 deg. F. 40-46 deg. F.
Ridge Top Winds: West NW NW
Expected snowfall: 0 in. 0 in. 0 in.
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