Avalanche Advisory: Monday - Feb 12, 2018

 
 
 
 
 
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THIS AVALANCHE ADVISORY EXPIRED ON February 13, 2018 @ 7:00 am
Avalanche Advisory published on February 12, 2018 @ 7:00 am
Issued by Josh Feinberg - Eastern Sierra Avalanche Center

MODERATE avalanche danger may develop today and tonight in isolated exposed areas at tree line and above where up to 3-4” of new snow falling could be blown into small wind slabs by light winds.  If winds or snowfall amounts exceed expectations, these wind slabs will likely become more wide-spread and dangerous.      

2. Moderate

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Above Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

2. Moderate

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Near Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

1. Low

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Below Treeline
Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
    Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
Avalanche Problem 1: Wind Slab
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    Certain
    Very Likely
    Likely
    Possible
    Unlikely
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    Very Large
    Large
    Small

Small isolated wind slabs sensitive to human triggering may develop today and tonight in exposed areas at tree line and above as a result of light snow showers picking up throughout the day accompanied by light westerly winds, shifting out of the northeast in the afternoon.  With 10-15mph winds with gusts only expected up to 30mph, and 3-4” of new snow, these wind slabs will likely form only on the leeward side of the more wind-prone exposed areas, below ridgelines, the sidewalls of gullies, and across higher elevation exposed slopes.  Be on the lookout in these types of areas for deposits of deeper smooth dense snow, snow being blown across the surface, and for signs such as shooting cracks from your skis to indicate that new wind deposits could be sensitive to human triggering.  In areas that snowfall and/or winds exceed expectations, fresh wind-slabs will likely be more widespread and dangerous.  Be wary of all aspects, as the winds shift from out of the west to the northeast mid-day.  

Firm underlying old snow in the form of melt-freeze crusts to firm windboard will act as good bed-surfaces for any new snow deposits to slide on, in addition for humans to slide on!  Crampons and ice-axs remain a good idea, and even essential on many mid to upper elevation steep slopes.  And watch out for obstacles!   

advisory discussion

In addition to the fresh wind slabs that will likely form today into tonight as mentioned above, there is a small possibility that some isolated small wind slabs formed yesterday and last night as the result of very strong SW winds, which gusted over 100mph above ridge-tops.  The reason this concern is so limited is simply the lack of loose snow available for transport.  No new snow has fallen since Jan 25th.  Most slopes prior to today have either gone thru melt-freeze cycles and remained frozen yesterday, or else are mostly firm from already being heavily wind-effected.  There are however limited areas where patches of soft surface snow has remained.   Snow banners were seen yesterday afternoon over ridge-tops.  While most of this snow likely sublimated into the atmosphere, it is quite possible that in isolated areas some of this old snow was deposited into a small wind-slab that could be human triggered.  While an avalanche resulting from snow being transported prior to today’s new snowfall would likely be small, it could be enough to knock a rider off their feet and lead to a bad fall.  

Widepsread firm surface conditions, even with a few inches of new snow on top, can easily lead to a slide-for-life.  Crampons, ice ax or whipet are still a good idea on many steep mid to upper elevation slopes.  

 

 

Weather and CURRENT CONDITIONS
weather summary

The feel of winter is back in the Eastern Sierra, at least for the moment!  Leave your t-shirts in the drawer, as high temperatures will be in the mid to upper teens today around 10,000’, and scattered light snow showers are expected thru today, increasing into tonight, and possibly lingering into Tuesday morning, with up to 3-5” of total new snowfall.  Winds should be light out of the west with gusts up to 30mph at higher elevations, shifting out of the NE this afternoon.  This will be due to an upper level low-pressure system centered over the OR-NV-ID border this morning that will gradually move south over Mono County this afternoon and evening. 

For Tuesday, temperatures will remain cold, and winds will increase ahead of another light disturbance that could bring isolated flurries on Wednesday.  High pressure will then return thru the weekend, before another cold front pushes in from the north, again dropping temperatures significantly, and bringing in the possibility of more light snow showers. 

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8,000 ft. to 10,000 ft.
Monday Monday Night Tuesday
Weather: Partly cloudy then becoming mostly cloudy. Chance of snow in the morning, then widespread snow showers in the afternoon. Mostly cloudy. Scattered snow showers. Mostly cloudy. Isolated snow showers in the morning.
Temperatures: 21 to 29 deg. F. 11 to 16 deg. F. 26 to 32 deg. F.
Mid Slope Winds: West shifting to the northeast in the afternoon. Northeast Northeast
Expected snowfall: Up to 1 inch in. Up to 3 inches in. up to 1 inch in.
Over 10,000 ft.
Monday Monday Night Tuesday
Weather: Partly cloudy then becoming mostly cloudy. Chance of snow in the morning, then widespread snow showers in the afternoon. Mostly cloudy. Widespread snow showers in the evening, then scattered snow showers after midnight. Mostly cloudy. Isolated snow showers in the morning.
Temperatures: 14 to 19 deg. F. 6 to 12 deg. F. 18 to 26 deg. F.
Ridge Top Winds: West shifting to the northeast in the afternoon. Northeast Northeast
Expected snowfall: up to 1 inch in. p to 3 inch in. ip to 1 inch 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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