Eastern Sierra Avalanche Advisory - 4/1/17

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THIS AVALANCHE ADVISORY EXPIRED ON April 2, 2017 @ 6:14 am
Avalanche Advisory published on April 1, 2017 @ 6:14 am
Issued by Josh Feinberg - Eastern Sierra Avalanche Center
bottom line

Blizard today!!  15 ft of snow in 5 hours!!  ...APRIL FOOLS!! ;-)  Spring conditions return.  Clear skies, warm temperatures, and decreasing winds will allow slopes to warm throughout the day with sun exposure (easterly, then southerly, then westerly).  Natural and human triggered small loose wet avalanches will become increasingly possible, especially near rock bands which will heat surrounding snow more dramatically.  Even small wet slides are heavy and dense and could carry a rider into undesirable terrain or entrain enough snow to bury a person.  Start early and be off steep slopes before they become saturated and unsupportable.  Avoid being under or on top of cornices that could fail, and beware of very firm conditions before slopes soften to where a fall could result in a slide-for life even on less steep slopes.  Evaluate snow and terrain carefully and consider bringing crampons, ice ax and whippet.

How to read the advisory

Bottom Line

Blizard today!!  15 ft of snow in 5 hours!!  ...APRIL FOOLS!! ;-)  Spring conditions return.  Clear skies, warm temperatures, and decreasing winds will allow slopes to warm throughout the day with sun exposure (easterly, then southerly, then westerly).  Natural and human triggered small loose wet avalanches will become increasingly possible, especially near rock bands which will heat surrounding snow more dramatically.  Even small wet slides are heavy and dense and could carry a rider into undesirable terrain or entrain enough snow to bury a person.  Start early and be off steep slopes before they become saturated and unsupportable.  Avoid being under or on top of cornices that could fail, and beware of very firm conditions before slopes soften to where a fall could result in a slide-for life even on less steep slopes.  Evaluate snow and terrain carefully and consider bringing crampons, ice ax and whippet.

Avalanche Problem 1: Loose Wet
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As slopes warm, soften, and become wet throughout the day, natural and human triggered small loose wet avalanches will become increasingly possible.  Cold temperatures yesterday and last night (along with clear overnight skies) will have led to a solid thick surface freeze.  E-S-W facing slopes will be very firm before they begin to soften more slowly with sun exposure due to this solid freeze.  East facing slopes will soften first in the morning, followed by south, then west in the afternoon, and this softening will be intensified near cliffs and rock outcrops.  North-facing slopes will soften as well at lower elevations.  Pay attention to signs such as large pinwheels and sinking past your boot top as indicators of slopes becoming unstable, and that steep terrain on these aspects should be avoided.  The small amount of new snow that fell Thursday will lead to some sticky conditions as it softens, as well as to a possible increase in widespread small loose wet point releases.   

*Small isolated wind slabs may also be encountered at upper elevations where Thursday’s 1-4” of new wind-blown snow was deposited.  While unlikely, it is possible that some of these could be sensitive to human triggering, and caution should be taken in steep exposed areas where even a small wind slab popping could result in a bad fall.   

advisory discussion

We have fallen into a springtime pattern this month with periods of fast windy storms hitting our area followed by periods of clearing and sunshine.  Avalanche concern has been shifting back and forth between concern over new sensitive wind slabs as we receive new snow and wind, to loose-wet avalanches as the sun comes back out and temperatures rise.  1-4” of new snow fell Thursday accompanied by high winds (which began out of the SW and then shifted out of the N) which brought avalanche concern to small isolated wind slabs.  Today we are back to full sunshine and warm temperatures, shifting the concern back to small loose-wet activity as firm frozen slopes soften and melt.  Along with avalanche concern, very firm conditions exist either where the wind has swept slopes and/or where slopes are frozen before they warm and soften.  Falls in many places could result in a slide-for-life.  Depending on your objective, crampons, ice ax and whippet are advisable.    

weather

Our spring-time pattern continues with brief low accumulation storms and high winds followed by periods of clearing and sunny skies.

Saturday will be a sunny warm spring day.  Expect highs in the low 40s around 10,000’, and light to moderate NE winds with ridgetop gusts up to 50mph, diminishing throughout the day. 

Sunday will be just about the same except for only light NW winds, before a weak disturbance moves quickly thru the area Sunday night into Monday morning bringing a trace of snow or drizzle and some increased north wind.     

Long Term: A brief high pressure ridge bringing warm dry conditions returns thru mid week, before yet another fast short-wave disturbance breaks it down on Thursday, leading the way for more pacific moisture and multiple waves of moisture thru the weekend. 

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: Sunny. Clear then becoming partly cloudy. Sunny.
Temperatures: 40 to 46 deg. F. 24 to 32 deg. F. 38 to 44 deg. F.
Wind direction: NE Light NW
Wind speed: 10 to 20 mph with gusts to 30 mph Light winds 10 to 15 mph
Expected snowfall: 0 in. 0 in. 0 in.
Over 10,000 ft.
  Saturday Saturday Night Sunday
Weather: Sunny. Clear then becoming partly cloudy. Sunny.
Temperatures: 37 to 43. deg. F. 23 to 28 deg. F. 35 to 41 deg. F.
Wind direction: NE Light NW
Wind speed: 15 to 25 mph with gusts to 50 mph decreasing to 10 to 20 mph with gusts to 35 mph in the afternoon. Light winds 10 to 15 mph with gusts to 25 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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