Avalanche Advisory: Sunday - Jan 27, 2019

THIS AVALANCHE ADVISORY EXPIRED ON January 28, 2019 @ 6:42 am
Avalanche Advisory published on January 27, 2019 @ 6:42 am
Issued by Steve Mace - ESAC

Avalanche danger will rise to MODERATE at low and mid elevations today while remaining LOW at upper elevations.  Temperatures remained above freezing overnight with a low of 35° recorded at the summit of Mammoth Mountain (11,000’).  Loose wet avalanches will be possible at all elevations particularly on more solar aspects.  It may be possible to find isolated pockets of wind slab at upper elevations or in extreme terrain.  While Persistent Slab avalanches will be unlikely today the consequence of triggering one is very high. Safe travel protocols are recommended. 

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
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Loose wet avalanches will be possible today.  This will be most concerning on solar aspects however temperatures remained above freezing last night even at upper elevations. It will not be impossible to find loose wet activity on more shaded aspects at lower elevations.  Wet snow surface, roller balls and snow shedding off of cliffs and trees are all signs of increasing hazard.  While resulting loose wet avalanches are likely to be small, they could be large enough to cause a fall or carry a skier through unpleasant terrain. 

Avalanche Problem 2: Persistent Slab
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While it has now been over a week since we have received reports of persistent slab avalanches the structure remains poor.  Loose faceted snow continues to be found near the bottom of the snowpack underlying a well-consolidated slab. This layer seems to be more reactive in areas where the snowpack is generally thinner.  Well preserved buried surface hoar continues to be found in specific areas particularly at low and mid elevations in more sheltered locations.  Keep an eye out for signs of instability such as recent avalanches, shooting cracks or wumphing and dig in to investigate these layers. Forecaster confidence in the distribution and sensitivity of persistent slabs is low. Triggering a persistent slab avalanche will be unlikely, but a resulting avalanche may be catastrophic.

Avalanche Problem 3: Wind Slab
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Winds have shifted around the compass over the last 24hr.  Although loose snow available for transport is limited, it will not be impossible to find isolated pockets of wind slab at upper elevations or in extreme terrain. With temperatures expected to be well above freezing today expect to see these wind slabs become more sensitive, especially on solar aspects .

advisory discussion

High temperatures have been the driving force of change to the snowpack over the past couple of days. A low of 35° recorded last night at the summit of Mammoth Mountain (11,000’). It’s likely that continued high temperatures today will increase the sensitivity of all of our avalanche problems.  It's also important to remember that we're dealing with a complex snowpack right now.  While a healing trend has been noted in many areas, the presence of two persistent weak layers within a meter of the surface in some areas is concerning. Remember that avalanches are possible even in times of relatively low danger. Safe travel protocols such as limiting your exposure to one skier at a time are always recommended. 

recent observations
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01/26- Preserved Surface Hoar and Propagating results in the Shwerwins- Mammoth area

01/26- Mammoth Rock Snowpack

01/26- Buried Surface hoar in the Mammoth rock area

01/26- Matterhorn snow conditions- Bridgeport Area

Weather and CURRENT CONDITIONS
weather summary

Warm, mild weather will continue today with partly cloudy skies and temperatures expected to reach a high of 43° at upper elevations.  Winds will be light to moderate out of the northwest. Temperatures are expected to drop below freezing tonight as light winds continue and shift more to the north. 

For tomorrow expect to see cloud clover increase as winds shift more to the north.  Temperatures will be similar tomorrow reaching a high of 40° at upper elevations.

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8,000 ft. to 10,000 ft.
Sunday Sunday Night Monday
Weather: Partly cloudy. Partly cloudy. Mostly cloudy.
Temperatures: 40 to 50. deg. F. 28 to 34. deg. F. 39 to 49. deg. F.
Mid Slope Winds: Light winds. North 10 to 15 mph with gusts to 25 mph in the evening becoming light. Light winds becoming northeast 10 to 15 mph with gusts to 30 mph in the afternoon.
Expected snowfall: None in. None in. None in.
Over 10,000 ft.
Sunday Sunday Night Monday
Weather: Partly cloudy. Partly cloudy. Mostly cloudy.
Temperatures: 33 to 43. deg. F. 23 to 28. deg. F. 30 to 40. deg. F.
Ridge Top Winds: Northwest 15 to 20 mph with gusts to 30 mph. North 10 to 15 mph with gusts to 25 mph. North 15 to 20 mph with gusts to 30 mph.
Expected snowfall: None in. None in. None 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 Avalanche Advisory is provided by the Eastern Sierra Avalanche Center, who is solely responsible for its content.

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