Eastern Sierra Avalanche Advisory - 3/11/17

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THIS AVALANCHE ADVISORY EXPIRED ON March 12, 2017 @ 1:38 am
Avalanche Advisory published on March 11, 2017 @ 1:38 am
Issued by Josh Feinberg - Eastern Sierra Avalanche Center
bottom line

Warming slopes resulting in small loose-wet point releases is the main avalanche concern for today (Saturday).  These could be large enough to knock riders of balance, and in rare instances could entrain enough snow to potentially bury a person.  These natural releases will be increasingly likely with prolonged sun exposure on slopes, and riders on these steep slopes could likely start these small slides with their turns. Pinwheels and roller-balls are signs that slopes are decreasing in stability, as is sinking past your boot-top in wet snow.  More concerning than avalanches is potentially firm snow conditions that could result in a slide-for-life.    

How to read the advisory

Bottom Line

Warming slopes resulting in small loose-wet point releases is the main avalanche concern for today (Saturday).  These could be large enough to knock riders of balance, and in rare instances could entrain enough snow to potentially bury a person.  These natural releases will be increasingly likely with prolonged sun exposure on slopes, and riders on these steep slopes could likely start these small slides with their turns. Pinwheels and roller-balls are signs that slopes are decreasing in stability, as is sinking past your boot-top in wet snow.  More concerning than avalanches is potentially firm snow conditions that could result in a slide-for-life.    

Avalanche Problem 1: Loose Wet
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  • Size ?
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    Increasing Danger

Air temperatures are again forecasted to reach almost 50 degrees F at 10,000’ today. These warm air temperatures combined with mostly sunny to partly cloudy skies and low winds will warm and moisten slopes, beginning with easterly facing in the morning and moving to westerly facing in the afternoon, with increased effects on slopes with southern exposure.  Small point releases will become likely on these slopes.  Small point releases are concerning as they could knock a person off balance in steep terrain or could potentially entrain enough snow to bury someone especially if the slope ends in a small gully.  These small slides are most likely to originate near warming rock bands, and could be triggered by a rider’s turns on steep slopes.  Get off slopes before they soften enough that you sink past your boot-top in wet snow.  If skies are cloudy, solar aspects will warm more slowly, and northern aspects at mid to low elevations could start seeing loose wet activity as well.

advisory discussion

Yesterday was a surprisingly cloudy day, keeping solar aspects (east to south to west) much firmer later in the day than the day before.  The very warm air temperature and clouds reflecting heat did cause them to soften however, and some small wet point releases were witnessed.  The warm air temps and clouds also caused northerly aspects below 9000’ to get moist and thick.  Today’s warm temps and lighter cloud cover (partly cloudy instead of mostly cloudy) will likely allow solar aspects to soften a big quicker, and increase the likelihood of small wet point releases.   

 The last snowfall in the area occurred on Sunday, and was accompanied by very strong SW winds through Monday.  Since then spring like conditions have dominated the region with above average temperatures, sunshine (except for yesterday) and low winds.  Windslabs that formed during the storm event have now stabilized, and the avalanche concern has shifted toward loose-wet point releases as slopes warm throughout the day from sun exposure and warm air temperatures.  Cold clear nights have for the most part refrozen the snow, but last night, especially around the mammoth area, cloudy skies kept temperatures warm and above freezing almost as high as 11,000’.  On the one hand, snow surfaces could soften more rapidly in areas where overnight clouds kept the snow surface warmer last night, but on the other hand continued clouds throughout the day could cut-down the sun slopes receive and lessen the amount they soften. 

Besides loose-wet snow instability, the combination of firm melt-freeze crusts on solar aspects before they soften and areas with firm wind-board on more northerly aspects create an even greater hazard to backcountry travelers with slide-for-life conditions.  Consider carrying and using crampons and an ice ax or whippet, and don’t be afraid to turn around or change your route due to firm conditions.

weather

Spring-like conditions will continue into at least early next week with above average warm temperatures, low winds, and mostly sunny to partly cloudy skies. 

Highs today (Saturday) will reach near 50 degrees at 10,000’, with partly cloudy skies, and calm to light winds. 

Sunday, expect more of the same, except skies should be clear of clouds.

Long-Term: High pressure with warm temperatures, clear skies and light winds should continue through early next week before a minor disturbance will likely bring some increased winds Tuesday and Wednesday afternoon.

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8,000 ft. to 10,000 ft.
  Saturday Saturday Night Sunday
Weather: Partly cloudy Partly cloudy then becoming clear Sunny
Temperatures: 50 to 56 deg. F. 27 to 33 deg. F. 53 to 58 deg. F.
Wind direction: Light Light Light
Wind speed: Light Light Light
Expected snowfall: 0 in. 0 in. 0 in.
Over 10,000 ft.
  Saturday Saturday Night Sunday
Weather: Partly cloudy Partly cloudy then becoming clear Sunny
Temperatures: 44 to 50 deg. F. 25 to 30 deg. F. 42 to 50 deg. F.
Wind direction: Light Light Light
Wind speed: Light Light Light
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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