Avalanche Advisory: Thursday - Mar 29, 2018

 
 
 
 
 
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THIS AVALANCHE ADVISORY EXPIRED ON March 30, 2018 @ 6:45 am
Avalanche Advisory published on March 29, 2018 @ 6:45 am
Issued by Clancy Nelson - Eastern Sierra Avalanche Center

The avalanche danger will rise to MODERATE today as all elevations begin to thaw. Rapid warming, light winds, and sunny skies will make natural loose wet avalanches increasingly possible and human triggering increasingly likely. Carefully evaluate the snowpack for thaw instabilities such as rollerballs and deep boot penetration in wet snow. Features of heightened concern include gullies and cirques, especially near rocks and trees. Timing is critical to avoid the problem. Plan to be off of steep sunny slopes before the snow becomes too saturated with melt water.

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.

2. Moderate

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Below Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
    Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
Avalanche Problem 1: Loose Wet
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    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

The recent warming trend will continue today with highs expected to be even warmer than yesterday. Natural loose wet avalanche will become increasingly possible, and human triggered point releases increasingly likely as slopes thaw. Temperatures will climb quickly on E aspects and follow the sun across the sky to S and then W facing slopes. Evaluate the snowpack around you for the depth and extent of the melting. Rollerballs and small point releases indicate that the snow is losing cohesion and becoming more unstable. Specific terrain features that will increase the risk of thaw instabilities include gullies and cirques, rock bands and trees, steep sunny slopes, and especially areas that will experience deeper melting for the first time today. Upper elevation solar aspects and lower elevation northerly aspect may warm more today than they have before increasing the risk of new loose wet avalanches. Timing is critical to avoid the problem. Plan to be off of steep sunny slopes before the snow becomes too wet.

advisory discussion

High pressure over the Southwest increases the warming trend today. Hourly forecasts across our area show rapid warming beginning mid-morning and continuing through the afternoon at all elevations. Snow levels are set to rise to 9000’ by evening. Typical spring thaw instabilities are expected to accompany the balmy weather. As the sun rises it will heat E aspects first, then S, then W by afternoon. Lower elevations will heat up before higher elevations. Wet snow melting at the surface will lose cohesion and become less and less stable as it warms through. Rollerballs coming down the slope around you and sinking into wet snow above your boot tops are signs of increasingly unstable conditions. The daily melt cycle has repeated itself already at middle and lower elevations on more southerly slopes. Higher elevation E-S-W aspects, and low elevation NE and NW aspects, may see more warming today than they have before. Specific terrain features that increase the risk of deep thawing include areas that will receive and retain more solar radiation. Gullies, bowls, and cirques will warm more than open slopes. Steep rocky terrain or slopes with tree cover are suspect. Areas with shallow, low density snow cover often become unstable first.

Even small loose wet avalanches can be dangerous if they carry you into hazardous terrain. They are heavy and hard to escape. And smaller point releases often indicate that larger and more dangerous wet slides are becoming possible. The good news is that you can avoid the problem all together. Timing is everything. Plan to be off of steep sunny slopes before they warm too deeply. Riding slush is no fun anyhow, so why risk it?

Weather and CURRENT CONDITIONS
weather summary

Expect dry and warm weather through Easter weekend. Slowly weakening high pressure over the southwest US will keep the region in a quiet weather pattern through Saturday with a slight increase in clouds going into the weekend.

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: Sunny. Partly cloudy then becoming clear. Sunny then becoming partly cloudy.
Temperatures: 50 to 56 deg. F. 27 to 32 deg. F. 51 to 59 deg. F.
Mid Slope Winds: Light winds. Light winds. Light winds.
Expected snowfall: 0 in. 0 in. 0 in.
Over 10,000 ft.
Thursday Thursday Night Friday
Weather: Sunny. Partly cloudy then becoming clear. Sunny then becoming partly cloudy.
Temperatures: 43 to 48 deg. F. 25 to 30 deg. F. 44 to 49 deg. F.
Ridge Top Winds: N Light winds. SW
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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