Avalanche Advisory: Saturday - Mar 31, 2018

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THIS AVALANCHE ADVISORY EXPIRED ON April 1, 2018 @ 6:37 am
Avalanche Advisory published on March 31, 2018 @ 6:37 am
Issued by Clancy Nelson - Eastern Sierra Avalanche Center

Near and below treeline the avalanche danger will quickly increase to MODERATE today as the snow thaws. Loose wet avalanches will become possible on steep slopes and especially in rocky or vegetated terrain. Above treeline, the danger for loose wet avalanches will be LOW where triggering even a larger avalanche will not be impossible, but the problem is expected to be more isolated. Watch for rollerballs and wet snow at the surface.

Early in the day firm snow conditions may be a slide-for-life hazard in steep consequential terrain. Crampons, ice axes, and a helmet can reduce your vulnerability in a event of a slip and fall.

1. Low

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Above Treeline
Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

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

Loose wet avalanches will again be a problem today as snow thaws and becomes less cohesive on steep slopes. Lower elevations that re-froze poorly overnight will develop wet snow quickly today. Northerly slopes, where the greenhouse effect kept the snow soft last night, will be more likely to have loose wet sluffs than previously. Rollerballs and boot-top penetration into wet snow are clues that you should move to less steep terrain. It will become increasingly possible to trigger small, or even large, loose wet avalanches today as temperatures climb in the lower elevation bands. At upper elevations triggering even a large wet sluff will not be impossible, but the problem will be more isolated to extreme terrain.

advisory discussion

Temperatures will be a few degrees cooler today than yesterday with partly cloudy skies and an increase in SW winds. Clouds will reduce the amount of incoming solar radiation, and moderate winds may provide some convective cooling at the snow surface. Combine today’s forecast with a solid re-freeze last night and you can expect lower chances of loose wet avalanches. That’s the situation that should play out today at higher elevations where any larger avalanches will most likely be limited to extreme terrain. At middle and lower elevations, however, the risk of triggering loose wet slides will be higher. Hazy clouds overnight and above freezing temps may have prevented the snow from setting up. So as the sun burns through the clouds today it will quickly warm steep slopes near and below treeline. At all elevations, specific terrain configurations will make the problem worse. Cirques and bowls, and rocky gullies will receive and retain more heat than open slopes. Loose wet avalanches often originate from cliffs or trees. Solar aspects will warm first and fast.

That’s all pretty complicated. But no matter where you plan to ride today, as the snow warms and thaws remember to look around for obvious signs of increasing instability. Pay attention the the extent and depth of the warming. Pinwheels or rollerballs coming down the hill around you indicate that the surface is losing cohesion. Boot-top penetration into wet snow is a sign that conditions are deteriorating. Move to shady, less steep terrain by the time the snow warms through and you can avoid the problem.

recent observations

Overnight LOWs (as of 5am) and Duration of Freeze:

Virginia Ridge, 9409’:  35 deg F, no freeze
Tioga Pass, 9972’:      27 deg F. 7hrs freezing
Agnew Pass, 9355’:    29 deg F, 4hrs freezing
June Mt., 9148’:          37 deg F, no freeze
Mammoth Pass, 9500’: 31 deg F, 1hr freezing
Sesame Plot, 9014’:    38 deg F, no freeze
Ch. 22-MMSA, 10,067’: 37 deg F, no freeze
Summit-MMSA, 11,053’: 30 deg F, 5hrs freezing
Rock Creek, 9600’:      28 deg F, 5hrs freezing
South Lake, 9580’:    26 deg F, 7hrs freezing
Sawmill, 10,200’:        26 deg F, freezing between 10pm and 2am

3/29- Thawing on Red Cone

3/29- Esha Canyon

Weather and CURRENT CONDITIONS
weather summary

Temperatures will remain well above average over the weekend with periods of high clouds in the forecast for our region and increase winds Sunday into Monday.

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8,000 ft. to 10,000 ft.
Saturday Saturday Night Sunday
Weather: Mostly cloudy then becoming partly cloudy. Partly cloudy then becoming clear. Sunny.
Temperatures: 50 to 58 deg. F. 28 to 33 deg. F. 50 to 58 deg. F.
Wind Direction: Light winds. W Light winds.
Wind Speed: Light winds. 10 to 15 mph with gusts to 30 mph in the evening becoming light. Light winds.
Expected snowfall: 0 in. 0 in. 0 in.
Over 10,000 ft.
Saturday Saturday Night Sunday
Weather: Mostly cloudy. Partly cloudy then becoming clear. Sunny.
Temperatures: 42 to 49 deg. F. 25 to 30 deg. F. 43 to 50 deg. F.
Wind Direction: SW W SW
Wind Speed: 15 to 25 mph with gusts to 35 mph. 10 to 20 mph. Gusts up to 35 mph in the evening. 15 to 20 mph with gusts to 35 mph.
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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