Avalanche Advisory: Wednesday - Feb 14, 2018

THIS AVALANCHE ADVISORY EXPIRED ON February 15, 2018 @ 6:29 am
Avalanche Advisory published on February 14, 2018 @ 6:29 am
Issued by Josh Feinberg - Eastern Sierra Avalanche Center

Avalanche danger is MODERATE for isolated wind slabs on upper elevation slopes especially in the June Lake to Lee Vining areas which received up to 8" of new snow Monday and Monday night, compared with 2-3" for most other areas. This new snow was accompanied by moderate to strong NE winds thru yesterday afternoon.  Light to moderate SW winds today could form small fresh wind slabs on slopes that were stripped by the previously stronger NE winds.  Be wary of pockets of dense wind deposited snow on all aspects especially just below ridgelines and on the sidewalls of gullies.   

2. Moderate

?

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

2. Moderate

?

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

1. Low

?

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
  • Type ?
  • Aspect/Elevation ?
  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

Light snow fell around our region on Monday and Monday night.  Most areas only received up to a few inches of new snow at higher elevations, while areas around June Lake and Lee Vining received up to 8” of light snow due to Mono Lake-effect upslope flow.  This new snow was accompanied by moderate to strong NE winds at tree-line and above, gusting up to 70mph at times over ridge tops yesterday morning.  On Monday afternoon fresh knee-high drifts were observed along the ridge-top of the Negatives from snow being stripped by upslope winds from the top of NE facing slopes.  Today, light winds with moderate gusts are forecasted to be out of the SW, which could deposit small fresh wind slabs on these previously stripped slopes. 

Isolated wind slabs with lingering sensitivity to human triggering could be found on NW-W-S-SE facing slopes, while small fresh sensitive wind slabs could form today on NW-N-E-SE facing slopes.  These are most likely to be found at tree-line and above just below ridgelines, on the sidewalls of gullies, and around other features that promote drifting.  Be on the lookout for areas with deeper, denser snow deposits, and watch for signs such as shooting cracks from your skis indicating that new wind deposits are likely sensitive to human triggering.

advisory discussion

The thin snowpack is still of great concern, not only for the water situation in California, but for barely hiding obstacles under its surface.  Be careful out there!  Firm melt-freeze surfaces and old firm wind-board with just a few inches of new fluffy snow on top still pose slide-for-life conditions in many areas.  The need for such tools as an ice-ax, crampons and a whippet haven’t gone away for steeper alpine objectives. 

recent observations

New snow amounts from Monday and Monday night are reported to be around 3" in the Mammoth area, and closer to 8" at upper elevations in the June area.

2/13: VA Lakes - Small isolated sensitive windslabs

2/12: June - Negatives - Wind loading

2/12: Mammoth Crest - Blue Crag - New snow and light winds

 

Weather and CURRENT CONDITIONS
weather summary

Slightly warmer temperatures, light SW winds with moderate gusts above ridgetops, and sunny skies are on tap for today.  A weak low-pressure system impacting north-eastern CA will bring in some clouds in the afternoon, and a potential flurry or two after midnight. 

For Thursday thru Sunday expect sunny skies and warming temperatures thru the weekend before another weak, but potentially slightly stronger storm, moves in Sunday night thru Monday, hopefully leaving more than a trace of new snow, and ushering in much colder temperatures for the rest of the week. 

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8,000 ft. to 10,000 ft.
Wednesday Wednesday Night Thursday
Weather: Sunny then becoming mostly cloudy. Partly cloudy. Isolated snow showers after midnight. Partly cloudy then becoming sunny. Isolated snow showers in the morning.
Temperatures: 28 to 36 deg. F. 12 to 17 deg. F. 28 to 34 deg. F.
Wind Direction: Southwest Southwest Light winds
Wind Speed: 10 to 15 mph. Gusts up to 25 mph in the afternoon. 10 to 15 mph in the evening becoming light. Gusts up to 30 mph. Light winds. Gusts up to 35 mph in the afternoon,
Expected snowfall: 0 in. Trace in. Trace in.
Over 10,000 ft.
Wednesday Wednesday Night Thursday
Weather: Sunny then becoming mostly cloudy. Partly cloudy. Isolated snow showers after midnight. Partly cloudy then becoming sunny. Isolated snow showers in the morning.
Temperatures: 21 to 26 deg. F. 7 to 12 deg. F. 22 to 27 deg. F.
Wind Direction: Southwest Southwest North
Wind Speed: 15 to 20 mph with gusts to 30 mph. 15 to 25 mph with gusts to 35 mph. 15 to 25 mph. Gusts up to 30 mph increasing to 45 mph in the afternoon.
Expected snowfall: o in. Trace in. Trace 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.

ESAC receives support from ...