Avalanche Advisory: Tuesday - Feb 20, 2018

THIS AVALANCHE ADVISORY EXPIRED ON February 21, 2018 @ 6:26 am
Avalanche Advisory published on February 20, 2018 @ 6:26 am
Issued by Josh Feinberg - Eastern Sierra Avalanche Center

The avalanche danger rating has dropped to LOW for today.  Be on the lookout for small isolated wind slabs in steep upper elevation terrain that may remain sensitive to human triggering.  Slide-for-life conditions and obstacles still abound! 

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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    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
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    Very Large
    Large
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Snowfall amounts were on the low-end of the spectrum for yesterday’s storm, with storm totals not exceeding a few inches by much for the most part.  Winds decreased significantly by mid-morning yesterday as they shifted from out of the SW to out of the NW, and little new snow transport occurred after that.  Some isolated drifted areas were found yesterday to be over a foot deep, with slab-like characteristics.  Winds are forecasted to be light today.  The greatest avalanche concern today is for lingering isolated small wind slabs in steep upper elevation terrain.  While these have had almost an entire day to settle, it is possible that some could still remain sensitive to human triggering.  Be on the lookout for these isolated slabs of denser snow below ridgelines, in the sidewalls of gullies, and around other features that promote drifting on all aspects.  Look for signs such as shooting cracks from your skis indicating unstable snow.        

advisory discussion

The CONSIDERABLE danger rating yesterday ended up being a conservative call, as new snowfall totals ended up being on the minimal end of the forecasted 2-6” spectrum.  While 2” is certainly enough snow for the right winds to transport into dangerous wind slabs, this did not appear to materialize as much as expected yesterday due to the very light low-density of the new snow combined with its timing in relation to how the winds played out.  It’s important to keep in mind that this statement is based off of limited observations and data, and that new concerning wind slabs did form yesterday morning in some areas, but certainly not nearly as widespread as feared.

On another note, June Lake appeared to have received at least an additional 2” of new snow yesterday afternoon / evening, while most other areas received a trace.  This can most likely be attributed to Mono-Lake, and its effect on increased snowfall amounts for these types of cold inside slider storms.  This extra snow’s low density and the associated light winds won’t add much to the avalanche concern.   

recent observations
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-2/19: Mammoth - Minaret Vista - Wind Slabs

-2/19: Mammoth - Redcone - Light new snow, cold temps

-2/18: Bishop to Mammoth - Turbulent snow transport

-2/17: June - Negatives - increasing winds, snow stability

 

 

Weather and CURRENT CONDITIONS
weather summary

A low-pressure trough will remain over us thru the week keeping temperatures well below average.  For today expect highs in the mid-teens around 10,000’, light westerly winds, and sunshine. 

Another small disturbance similar to the last one will move thru the region tomorrow night into Thursday morning, only without the strong winds, bringing similarly low moisture amounts.  The low-pressure trough sitting over us will keep the storm door open and the weather pattern active through the following weeks into March.  While these storms appear to be similar “inside-sliders” like the last one, there is finally some talk of the possibility of some stronger storms for the beginning of March coming out of the Gulf of Alaska.  Fingers crossed! 

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8,000 ft. to 10,000 ft.
Tuesday Tuesday Night Wednesday
Weather: Sunny Mostly cloudy. Slight chance of snow showers after midnight. Mostly cloudy. Chance of snow showers.
Temperatures: 12 to 22 deg. F. 2 to 7 deg. F. 15 to 25 deg. F.
Mid Slope Winds: Light Light Light
Expected snowfall: 0 in. 0 in. up to 1 inch in.
Over 10,000 ft.
Tuesday Tuesday Night Wednesday
Weather: Sunny Mostly cloudy. Slight chance of snow showers after midnight. ostly cloudy. Chance of snow showers.
Temperatures: 7 to 17 deg. F. -2 to 3 deg. F. 8 to 18 deg. F.
Ridge Top Winds: West Light Light
Expected snowfall: 0 in. 0 in. up to 1 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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