Avalanche Advisory: Sunday - Feb 18, 2018

THIS AVALANCHE ADVISORY EXPIRED ON February 19, 2018 @ 6:52 am
Avalanche Advisory published on February 18, 2018 @ 6:52 am
Issued by Josh Feinberg - Eastern Sierra Avalanche Center

Avalanche danger will remain LOW through most of today, despite very strong SW winds at all elevations, due to the limited amount of loose snow that is available for transport.  Isolated small new wind slabs sensitive to human triggering may form in more sheltered mid to low elevation areas where greater amounts of loose snow is likely to exist.  For areas that receive the upper end of the 1-6” of new snow forecasted for tonight into tomorrow, avalanche danger will increase to MODERATE for wind slabs.  *Be aware of widespread firm windswept surfaces and frozen melt-freeze crusts creating slide for life conditions, and the many obstacles that exist do to our shallow snowpack.  

1. Low

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

1. Low

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

1. Low

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Below Treeline
Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
    Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
Avalanche Problem 1: Wind Slab
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  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

Very strong SW winds at all elevations today could form isolated small wind slabs around features that promote drifting that could be sensitive to human triggering.  This concern may actually be greater at mid to lower elevations in typically more sheltered locations at all aspects, as very little loose snow is available for transport at more exposed higher elevations.  If snowfall amounts exceed the up to 1” expected today, this concern will be greater.  Be on the lookout for patches of fresh smooth dense snow, and watch for shooting cracks from your skis indicating potentially unstable fresh wind slabs.  Tonight into tomorrow snowfall is expected to increase with up to a few inches of new snow tonight and a couple more inches tomorrow.  This new snow, along with decreasing winds more ideal for wind slab formation, will likely increase avalanche danger to MODERATE for tonight and tomorrow in the more usual wind deposition areas below ridgelines and across gullies. 

advisory discussion

The light 2-8” of new snow that fell a week ago was followed by a period of strong shifting winds, leaving many exposed mid to upper elevation areas wind effected with either wind slab / wind board, or wind stripped surfaces.  The isolated wind slabs that did form have had plenty of time to stabilize.  The clear sunny skies and warmer temperatures over the past few days have led to melt freeze crust formation on solar aspects.  (E-SE-S-SW).  All these firm surfaces present slide for life conditions making crampons, ice ax and whippets prudent for travel in steep exposed terrain.  Beware of the many obstacles that exist do to our shallow snowpack.   

Weather and CURRENT CONDITIONS
weather summary

A wind advisory is in effect until 10pm this evening.  A strong cold front is making its way south into our region today, moving thru this evening, bringing strong SW winds, cold temperatures, and scattered snow showers.  Winds gusts are likely up to 75mph even at low elevations, with 100mph gusts over ridge tops.  Up to an inch of accumulation could be possible this afternoon and evening.  Expect high temperatures in the low 30s near 10,000’, dropping significantly this evening and tonight into the single digits even at low elevations.

As the cold front passes this evening, a few inches of accumulation could be possible tonight, and a couple more inches possible tomorrow.  Winds will gradually decrease, but very cold temperatures will remain thru the week, with the coldest temperatures yet this season on Monday and Tuesday.   

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. Chance of snow showers. Mostly cloudy. Chance of snow showers. Mostly cloudy. Chance of snow showers.
Temperatures: 32 to 40 deg. F. 4 to 9 deg. F. 13 to 19 deg. F.
Wind Direction: Southwest Southwest becoming west after midnight Northwest
Wind Speed: 20 to 30 mph increasing to 25 to 40 mph in the afternoon. Gusts up to 75 mph. 30 to 40 mph with gusts to 75 mph becoming west 20 to 30 mph with gusts to 50 mph after midnight. 15 to 25 mph with gusts to 40 mph.
Expected snowfall: up to 1 in. 1-3 in. up to 2 in.
Over 10,000 ft.
Sunday Sunday Night Monday
Weather: Partly cloudy. Chance of snow showers. Mostly cloudy. Snow showers likely. Mostly cloudy. Snow showers likely.
Temperatures: 26 to 32 deg. F. 0 to 5 deg. F. 6 to 11 deg. F.
Wind Direction: Southwest Southwest becoming west after midnight Northwest
Wind Speed: 45 to 65 mph. Gusts up to 85 mph increasing to 95 mph in the afternoon. 45 to 60 mph with gusts to 95 mph becoming west and decreasing to 30 to 45 mph with gusts to 60 mph after midnight. 20 to 30 mph with gusts to 40 mph.
Expected snowfall: up to 1 in. 1 to 4 in. up to 2 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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