Eastern Sierra Avalanche Advisory - 2/15/17

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THIS AVALANCHE ADVISORY EXPIRED ON February 17, 2017 @ 5:14 pm
Avalanche Advisory published on February 15, 2017 @ 5:14 pm
Issued by Doug Lewis - Eastern Sierra Avalanche Center
bottom line

The primary avalanche concern for Wednesday thru Thursday will be increasing wind slabs at middle and upper elevations as pre-frontal winds increase Thursday. Wednesday, ahead of the next system warm temperatures will maintain the threat of loose wet avalanches on solar aspects at middle and lower elevations. Wednesday: Above about 9000 feet, natural avalanches are unlikely, but human triggered avalanches possible. Evaluate snow and terrain carefully and identify windloaded features such as below ridgelines and along the sidewalls of gullies. Thursday: natural avalanches possible; human- triggered avalanches likely on wind loaded slopes.

Wednesday: Below ~ 8000 feet, overall both natural unlikely and human triggered avalanches will be unlikely. Thursday, isolated pockets of Wind Slab may form in favored locations (gullies, shallow depressions, rock outcroppings, etc.) if the snowline falls further than forecasted. 

How to read the advisory

Bottom Line

The primary avalanche concern for Wednesday thru Thursday will be increasing wind slabs at middle and upper elevations as pre-frontal winds increase Thursday. Wednesday, ahead of the next system warm temperatures will maintain the threat of loose wet avalanches on solar aspects at middle and lower elevations. Wednesday: Above about 9000 feet, natural avalanches are unlikely, but human triggered avalanches possible. Evaluate snow and terrain carefully and identify windloaded features such as below ridgelines and along the sidewalls of gullies. Thursday: natural avalanches possible; human- triggered avalanches likely on wind loaded slopes.

Wednesday: Below ~ 8000 feet, overall both natural unlikely and human triggered avalanches will be unlikely. Thursday, isolated pockets of Wind Slab may form in favored locations (gullies, shallow depressions, rock outcroppings, etc.) if the snowline falls further than forecasted. 

Avalanche Problem 1: Wind Slab
  • Character ?
  • Aspect/Elevation ?
  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small
  • Trend ?
    Increasing Danger

Moderate Southwesterly winds accompanying the arrival of the next system Thursday will form wind slabs NW-N-NE-E-SE. Heightened avalanche conditions exist on NW-N-NE-E-SE wind loaded terrain at upper and middle elevations. Be wary of hollow, drum-like sounding snow or cracks shooting out from your feet.

advisory discussion

The precipitation from last week’s Atmospheric River with reports of extensive natural avalanches. Strong Southwesterly winds formed Wind Slabs on all aspects. As the system departed, the Southwest flow veered to the Northeast As the system departed, forming additional Wind Slabs primarily on NW-W-SW-S-SE aspects. Winds decreased through the early part of the week allowing the recently formed Wind Slabs to slowly stabilize. Winds are forecasted in increase Thursday with dense snowfall, which will begin a new round of Wind Slab instability throughout the the mid to upper elevations. 

Warming temperatures over the past few days helped to settle and strengthen the snowpack as a whole but southerly aspects began to shed some of the recent new snows with widespread Loose Wet avalanches, primarily below ~ 11,000’. The next system may well bring additional rain to the Lower elevations saturating the recent snowfall, which will increase the potential for Loose Wet releases. Be on the lookout for moist surface snow, pinwheels rolling down around you, and steep rocky terrain.

   

weather

...HIGH WIND WATCH IN EFFECT FROM LATE TONIGHT THROUGH THURSDAY AFTERNOON...

Dry conditions with increasing clouds ahead of the next system. Thursday will feature a windy day with mountain snow and lower valley rain. Friday into Saturday brings another system with less wind but additional rain and higher elevation snow. There will be a brief break before a much stronger storm brings wind and more significant precipitation early next 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. Mostly cloudy. Cloudy with snow.
Temperatures: 42 to 48 deg. F. 29 to 34 deg. F. 31 to 37 deg. F.
Wind direction: Light winds becoming southwest Southwest Southwest
Wind speed: 10 to 15 mph with gusts to 30 mph in the afternoon. 15 to 25 mph. Gusts up to 40 mph increasing to 70 mph after midnight. 20 to 35 mph with gusts to 85 mph.
Expected snowfall: 0 in. 0 in. up to 6 in.
Over 10,000 ft.
  Wednesday Wednesday Night Thursday
Weather: Sunny then becoming mostly cloudy. Mostly cloudy. Cloudy with snow.
Temperatures: 36 to 42 deg. F. 25 to 30 deg. F. 26 to 32 deg. F.
Wind direction: Light winds becoming southwest Southwest Southwest
Wind speed: 10 to 15 mph with gusts to 40 mph in the afternoon. 15 to 25 mph with gusts to 50 mph increasing to 25 to 35 mph with gusts to 85 mph after midnight. 40 to 60 mph. Gusts up to 110 mph increasing to 125 mph in the afternoon.
Expected snowfall: 0 in. 0 in. 2 to 6 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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