Avalanche Advisory: Thursday - Feb 15, 2018

 
 
 
 
 
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THIS AVALANCHE ADVISORY EXPIRED ON February 16, 2018 @ 6:31 am
Avalanche Advisory published on February 15, 2018 @ 6:31 am
Issued by Clancy Nelson - Eastern Sierra Avalanche Center

The avalanche danger remains MODERATE today. Recently deposited wind slabs may still be sensitive on NW-N-E facing alpine slopes. If the shifting winds are strong enough by this afternoon, fresh wind slabs may form on S-SW-W facing slopes, especially below ridgelines and in cross-loaded gullies. Natural avalanches are unlikely, but human triggered avalanches may be possible.

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
  • Size ?
    Historic
    Very Large
    Large
    Small

Continuous moderate to strong winds blew from the southwest through about midnight carrying snow onto E and NE facing slopes from Lee Vining to south of Mammoth. Several natural wind slab avalanches were observed in the June Lake area yesterday afternoon. Cold temperatures overnight may have slowed the bonding between these winds slabs and the old hard snow surface which means that human triggering may still be possible on N to NE facing alpine slopes today. Just below ridges, convexities, and cross-loaded gullies are the features of concern.

Winds are forecast to shift N today, increasing into the afternoon at upper elevations. In areas where the NE wind is strong enough, small new wind slabs may form on S-SW-W slopes, especially above treeline and where there is enough snow to slide on.

Look for cornices and round pillow shaped drifts which will indicate where older wind slabs have formed. Blowing snow will point to areas of newer drifting. Hollow sounding snow and shooting cracks are signs that wind slabs may be sensitive to human triggering.

advisory discussion

Several days of cold temperatures have brought the feel of winter back to the Sierra. We even got a few inches of light fluffy snow on Monday which covered over the hard crusts from early in the month. Moderate to strong winds have been redistributing that snow onto leeward slopes throughout the range. Several natrual avalanches were observed in the June Lake area yesterday. Some of these wind slabs may still be sensitive enough to trigger, especially early in the day. And if the shifting northerly winds are strong enough at upper elevations this afternoon fresh wind slabs may form just under south and west facing ridgelines. Watch for blowing snow to point towards newer wind deposits.

Obstacles abound in our area. The thin snowpack may have rocks and stumps lurking just under the surface. In steep alpine terrain, hard crusts and scoured areas still pose the threat of slide-for-life conditions in the event of a fall. Caution is advised, as well as crampons and ice axes.

recent observations
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2/14- Natural Wind Slab Avalanches, Negatives

2/14- Wind Transport in the Negatives

2/14- Consistent SW Winds Blowing Snow in the Mammoth Area

2/13- Isolated Sensitive Wind Slabs, Virginia Lakes

2/12- NE Winds Blowing Snow Up Slope, Negatives

Weather and CURRENT CONDITIONS
weather summary

A few light snow showers are possible through mid morning in Mono County, though no additional accumulation is expected. Cool northerly flow will keep temperatures below average today with gusty winds at the ridgetops as the front passes.

 

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8,000 ft. to 10,000 ft.
Thursday Thursday Night Friday
Weather: Partly cloudy then becoming sunny. Slight chance of snow showers in the morning. Clear. Sunny.
Temperatures: 28 to 34 deg. F. 11 to 17 deg. F. 40 to 46 deg. F.
Wind Direction: NE Light winds. Light winds.
Wind Speed: Light winds. Gusts up to 25 mph. Light winds. Light winds.
Expected snowfall: 0 in. 0 in. 0 in.
Over 10,000 ft.
Thursday Thursday Night Friday
Weather: Sunny. Slight chance of snow showers in the morning. Clear. Sunny.
Temperatures: 22 to 28 deg. F. 10 to 15 deg. F. 33 to 38 deg. F.
Wind Direction: N N W
Wind Speed: 10 to 15 mph with gusts to 30 mph increasing to 20 to 30 mph with gusts to 45 mph in the afternoon. 10 to 15 mph. Gusts up to 25 mph in the evening. 10 to 15 mph. Gusts up to 25 mph in the morning.
Expected snowfall: 0 in. 0 in. 0 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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